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Radio frequency identification by rfid project team . faculty of electronic engineering . communication department. menoufia university [combined and uploaded by a member of the team ( mohammed ali )]
 

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Radio Frequency Identification By RFID Project Team . Faculty of Electronic Engineering . Communication department
. Menoufia University Combined and uploaded by a member of the team ( Mohammed Ali )

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    Radio frequency identification by rfid project team . faculty of electronic engineering . communication department. menoufia university [combined and uploaded by a member of the team ( mohammed ali )] Radio frequency identification by rfid project team . faculty of electronic engineering . communication department. menoufia university [combined and uploaded by a member of the team ( mohammed ali )] Document Transcript

    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Menoufia University Faculty Of Electronic Engineering Department Of Electronics & Communication Engineering Graduation Project Supervised by Dr. Hend Abd-El Azim Malhat 2013 Supervisors Head of the Department Dean Radio Frequency Identification Antennas -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Preface ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ Preface The use of computerized systems to process information has changed lifestyles around the world. Many automated systems have been developed for information tracking and automated identification, simple decision response and control. Radio frequency identification (RFID) is one of several types of automatic identification (Auto-ID) procedures. Auto-ID procedures include barcode systems, contact-based smart cards, and biometrics such as voice and fingerprint identification. RFID is an emerging and leading technology in item identification. RFID is a wireless communication technology that is used to uniquely identifying tagged objects or people. The roots of RFID technology can be traced back to the World War II in which, the Germans discovered that if pilots rolled their planes while they were returning to base, the RFID tag changed the signal that was reflected back. This had allowed the German base to identify the planes as friendly fighters or not and is essentially a very basic RFID system. In RFID systems, a reader communicates to a transponder with an attached microchip that carries data and, in some systems, processes data. Data transfer occurs between a tag and a reader through their antenna coupling. Thus, the RFID tag and reader antennas play the major role in RFID system operation. In general, RFID tags can be categorized as active and passive. The active tags get their energy completely or partially from an integrated power supply, i.e., battery, while the passive tags do not have any power supply and rely only on the power extracted from the radio frequency signal received from the reader. The use of RFID depends on the frequency bands licensed by governments. Operating frequencies include 135 kHz, 13.56 MHz, 868 MHz (Europe), 915 MHz (USA), 2.45 GHz, and 5.8 GHz among others. The RFID tag and reader antennas play significant role in determining the covered zone, range and accuracy of communication. Different -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Preface ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ types of antennas have been introduced for RFID tag. The antennas include printed dipoles, folded dipoles, loop antennas, meander line printed antennas, and slot antennas. The antenna impedance should be inductive in order to achieve conjugate matching with the capacitive impedance of the IC-microchip. Adding an external matching network with lumped elements is usually prohibitive in RFID tags due to the cost and fabrication issues. Matching network has been added as an integral part to the tag to provide a better match for the chip capacitive impedance. There are several techniques to achieve complex impedance matching such as T-mach, the proximity-loop, loading bar, and the nested-slot layouts. Most of the previous work in the RFID tag antenna design does not include the effect of the object and the surrounding environments. Also, some of these tag antennas are designed and optimized for virtual IC-microchip, which is not practically available. Few RFID tag parameters are calculated in the published work such as return loss (reflection coefficient relative to 50 Ω), the input impedance, and the radiation pattern in free space. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | i Contents 1 Automatic Identification Systems 1-1 1.1 Introduction 1-1 1.2 Barcode systems 1-2 1.2.1 One-dimensional 1.2.2 Two-dimensional 1.2.3 Advantages of Barcode systems 1.2.4 Disadvantages of Barcode systems 1.2.5 Bar-coding 1.2.6 Advantages of 2-D Barcode systems 1.3 Optical character recognition 1-6 1.4 Biometric procedures 1-6 1.4.1 Voice identification 1.4.2 Fingerprinting procedures 1.4.3 Applications of Biometric procedures 1.4.4 Advantages of Biometric procedures 1.4.5 Disadvantages of Biometric procedures 1.5 Magnetic stripe card 1-8 1.5.1 The magnetic stripe 1.5.2 Magnetic stripe coercivity 1.5.3 How does a magnetic stripe on the back of a credit card work? 1.6 Smart cards 1-12 1.6.1 Memory cards 1.6.2 Microprocessor cards 1.7 Electronic Article Surveillance (EAS) 1-14 2 History of RFID 2-1 2.1 It All Started with IFF 2-1 2.2 RFID Technology 2-3 2.3 Components of an RFID System 2-4 2.4 Basic Operation 2-5 2.5 Different Types of RFID 2-5 2.5.1 Frequency bands are being used for RFID -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | ii 2.5.2 RFID tags are further broken down into two categories 2.5.3 There are two basic types of chips available on RFID tags, Read-Only and Read-Write 2.6 Advantages of the Technology 2-7 2.6.1 Contactless 2.6.2 Writable Data 2.6.3 Absence of Line of Sight 2.6.4 Variety of Read Ranges 2.6.5 Wide Data-Capacity Range 2.6.6 Support for Multiple Tag Reads 2.6.7 Rugged 2.6.8 Perform Smart Tasks 2.6.9 Read Accuracy 2.7 Disadvantages of the technology 2-15 2.7.1 Poor Performance with RF-Opaque and RF- Absorbent Objects 2.7.2 Impacted by Environmental Factors 2.7.3 Limitations on Actual Tag Reads 2.7.4 Impacted by Hardware Interference 2.7.5 Limited Penetrating Power of the RF Energy 2.7.6 Immature Technology 2.8 Applications 2-19 2.9 Security and Privacy Issues 2-21 2.9.1 Tag Data 2.9.1.1 Eavesdropping (or Skimming) 2.9.1.2 Traffic Analysis 2.9.1.3 Denial of Service Attack 2.9.2 RFID Reader Integrity 2.9.3 Personal Privacy 2.10 RFID Security Trends 2-22 2.10.1 Approaches for Tackling Security and Privacy Issues 2.10.1.1 Solutions for Tag Data Protection 2.10.1.2 Solutions for RFID Reader Integrity 2.10.1.3 Solutions for Personal Privacy 2.11 “RSA” Selective Blocker Tag 2-25 -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | iii Conclusion 2-25 3 RFID Chip Tag 3-1 3.1 Definition 3-1 3.2 Tag Characteristics 3-1 3.2.1 Identifier Format 3.2.2 Power Source 3.2.2.1 A passive tag 3.2.2.2 An active tag 3.2.2.3 A semi-passive tag 3.2.2.4 A semi-active tag 3.2.3 Operating Frequencies 3.2.3.1 Low Frequency (LF) 3.2.3.2 High Frequency (HF) 3.2.3.3 Ultra High Frequency (UHF) 3.2.3.4 Microwave Frequency 3.2.4 Functionality 3.2.4.1 Memory 3.2.4.2 Read Only (RO) 3.2.4.3 Write Once, Read Many (WORM) 3.2.4.4 Read Write (RW) 3.2.4.5 Environmental sensors 3.2.4.6 Security functionality, such as password protection & cryptography 3.2.4.7 Privacy protection mechanisms 3.2.5 Form Factor 3.3 Antennas 3-16 3.4 Basic Concepts 3-17 3.4.1 Tag Collision 3.4.2 Tag Readability 3.4.3 Information, Modulation, and Multiplexing 3.4.4 Backscatter Radio Links 3.4.5 Link Budgets 3.4.6 Reader Transmit Power 3.4.7 Path Loss 3.4.8 Tag Power Requirement 3.4.9 Factors which affect read range for RFID 3.4.9.1 Passive, BAP, NFC or Active RFID? 3.4.9.2 RFID Frequency 3.4.9.3 Surrounding materials -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | iv 3.4.9.4 Tag Type 3.4.9.5 Type of reader 3.4.9.6 Orientation 3.4.9.7 Time to read 3.4.9.8 Number of tags being read 3.4.9.9 Density of Tags Conclusion 3-32 Simulation & Results A-1 A. Half wave dipole antenna A-2 A.1 Radiation Pattern in different planes B. Printed Dipole antenna A-4 B.1 Radiation pattern in different planes RFID Chip Tag Analysis B-1 Numerical Results B-3 UHF tag models A. First model B. Second model Microwave tag models B-13 A. First model B. Second model 4 RFID Chip-less Tag 4-1 4.1 Introduction 4-1 4.2 Difficulties of achieving low cost RFID 4-1 4.3 Definition of Chip less RFID tag 4-1 4.4 Specifications for chip less RFID tag 4-1 4.4.1 Electrical specifications 4.4.2 Mechanical specifications 4.4.3 Commercial 4.5 Operation of the chip less RFID 4-2 4.6 Types of Chip less RFID tag 4-3 4.6.1 TDR-based chip less RFID tags 4.6.1.1 Non-Printable TDR-based 4.6.1.2 Printable TDR-based 4.6.1.2.1 Delay-line-based 4.6.2 Spectral signature-based chip less tags 4.6.2.1 Chemical tags -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | v 4.6.2.1.1 Nano-metric materials 4.6.2.1.2 Ink-tattoo chip less tags 4.6.2.2 Planar circuit chip less RFID 4.6.2.2.1 Capacitive tuned dipoles 4.6.2.2.2 Space-filling curves 4.6.2.2.3 LC Resonant 4.6.2.2.4 4.7 Chip less RFID tag 4-5 4.8 Spiral Resonators 4-6 4.9 Theoretical Modeling of Spiral Resonator 4-6 4.10 Spiral Resonator Modeling Using Distributed Components 4-7 4.11 Ultra Wideband Antennas 4-8 Simulation & Results C-1 A. Chip-less Tag (Rectangular) C-2 A.1 Variation of Frequency with length B. Chip-less Tag (Ellipse) C-4 B.1 Variation of Frequency with length 5 Modern RFID Readers 5-1 5.1 Introduction 5-1 5.2 RFID Reader Architecture 5-1 5.3 Review of RFID Readers 5-3 5.4 Towards Universal Reader Design 5-6 5.5 Proposed Chip-less RFID System 5-6 5.6 Review of Chip-less RFID Transponders 5-8 5.7 Chip-less RFID Transponders 5-10 5.8 Chip-less RFID Reader 5-12 5.9 Differences Between Chipped and Chip-less Tag Readers 5-13 5.10 Transceiver Specifications for Chip-less Tag Reader 5-14 5.11 Gen-1 Transceiver 5-16 5.12 Gen-2 Transceiver 5-19 5.13 UWB Transceiver 5-20 -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Contents ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــ‬‫ــــــــــــــــ‬ P a g e | vi 5.14 Chip-less RFID Tag-Reader System Components 5-23 5.15 RFID Reader Digital Control Section 5-24 5.16 Chip-less RFID Reader Tag Interrogation/Detec- tion Algorithm 5-25 5.17 Application Software for Chip-less RFID System 5-27 Conclusion 5-27 Simulation & Results D-1 A.1.1 Folded Dipole Antenna A.1.2 Simulated return losses of the proposed antenna A.1.3 Impedance A.1.4 Measured gain of the proposed antenna A.2 Measured radiation patterns at 922MHz for the proposed antenna References 1 -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 1 1 Automatic Identification Systems 1.1 Introduction In recent years, automatic identification procedures (Auto-ID) have become very popular in many service industries, purchasing and distribution logistics, industry, manufacturing companies and material flow systems. Automatic identification procedures exist to provide information about people, animals, goods and products in transit. The barcode labels that triggered a revolution in identification systems some considerable time ago are being found to be inadequate in an increasing number of cases. Barcodes may be extremely cheap, but their stumbling block is their low storage capacity and the fact that they cannot be reprogrammed. The technically optimal solution would be the storage of data in a silicon chip. The most common form of electronic data-carrying device in use in everyday life is the smart card based upon a contact field (telephone smart card, bank cards). However, the mechanical contact used in the smart card is often impractical. A contactless transfer of data between the data-carrying device and its reader is far more flexible. In the ideal case, the power required to operate the electronic data-carrying device would also be transferred from the reader using contactless technology. Because of the procedures used for the transfer of power and data, contactless ID systems are called RFID systems (Radio Frequency Identification). Figure 1.1: Overview of the most important auto-ID procedures. Auto - ID Barcode s 1-D 2-D OCR Biometri cs Voice identificatio n Fingerprinti ng procedures Magneti c stripe card Smart cards Memory cards Microprocess or cards EAS RFID -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 2 1.2 Barcode systems 1.2.1 One-dimensional Barcodes have successfully held their own against other identification systems over the past 20 years. The barcode is a binary code comprising a field of bars and gaps arranged in a parallel configuration. They are arranged according to a predetermined pattern and represent data elements that refer to an associated symbol. The sequence, made up of wide and narrow bars and gaps, can be interpreted numerically and alphanumerically. It is read by optical laser scanning, i.e. by the different reflection of a laser beam from the black bars and white gaps, as shown below. However, despite being identical in their physical design, there are considerable differences between the code layouts in the approximately ten different barcode types currently in use. Barcode systems require three elements: 1. Origin: You must have a source of barcodes. These can be preprinted or printed on demand. 2. Reader: You must have a reader to read the barcodes into the computer. The reader includes and input device to scan the barcode, a decoder to convert the symbology to ASCII text, and a cable to connect the device to your computer. 3. Computer system: You must have a system to process the barcode input. These can be single-user, multi-user, or network systems. The most popular barcode by some margin is the EAN code (European Article Number), which was designed specifically to fulfill the requirements of the grocery industry in 1976. Figure 1.2: Example of the structure of a barcode in EAN coding. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 3 The EAN code represents a development of the UPC (Universal Product Code) from the USA, which was introduced in the USA as early as 1973. Today, the UPC represents a subset of the EAN code, and is therefore compatible with it. The EAN code is made up of 13 digits: the country identifier, the company identifier, the manufacturer’s item number and a check digit (Figure 1.2). In addition to the EAN code, the following barcodes are popular in other industrial fields: • Code Coda bar: medical/clinical applications, fields with high safety requirements. • Code 2/5 interleaved: automotive industry, goods storage, pallets, shipping containers and heavy industry. • Code 39: processing industry, logistics, universities and libraries. 1.2.2 Two-dimensional Within the Auto-ID family, a new two-dimensional system of bar-coding has evolved which allows barcodes to hold more data than the traditional method. Data is encoded in both horizontal and vertical dimensions and, as more data is encoded, the size of the barcode can be increased in both the horizontal and vertical directions. Two-dimensional barcodes (Matrix Codes) are already being used for concert tickets by sending a barcode to a mobile phone and then scanning the message at the door by a laser gun. Bar codes and readers are most often seen in supermarkets and retail stores, but a large number of different uses have been found for them. 1.2.3 Advantages of Barcode systems  Fast and Reliable Data Collection.  10,000 Times better Accuracy.  Faster Access to Information. 1.2.4 Disadvantages of Barcode systems  Require line of sight to be read.  Can only be read individually (Can only be read one at a time).  Cannot be read if damaged or dirty.  Can only identify the type of item. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 4  Cannot be updated (Cannot be written to or reprogrammed).  Require manual tracking and therefore,  Susceptible to human error.  Low storage capacity, low read range.  They only represent a series of items and not an individual or unique item.  Durability (as mostly printed paper). 1.2.5 Bar-coding Barcodes are part of every product that we buy and has become the “ubiquitous standard for identifying and tracking products”, Traditional bar-coding is coupled with the Universal Product Code (UPC) and every day accounts for billions of scans all over the world. According to a survey conducted by Zebra Technologies in 2006, over 96% of European companies cited improved efficiency as the main benefit of using bar-coding. Other reasons that European companies gave for using barcodes were: increasing the accuracy of ordering and in-voicing (32%), cost reduction (26%), and the fact that newer technology isn’t ready yet (16%). Within the Auto-ID family, a new two-dimensional system of bar-coding has evolved which allows barcodes to hold more data than the traditional method. Figures show the differences between one- and two-dimensional barcodes. Product data is encoded in both horizontal and vertical dimensions and, as more data is encoded, the size of the barcode can be increased in both the horizontal and vertical directions thus maintaining a manageable shape for easy scanning and product packaging specifications. Two-dimensional code systems have become more feasible with the increased use of moving beam laser scanners, and Charge Coupled Device (CCD) scanners. The 2-D symbol can be read with hand held moving beam scanners by sweeping the horizontal beam down the symbol. However, this way of reading such a symbol brings us full circle back to the way 1D bar code was read by sweeping a contact wand across the symbol. The speed of sweep, resolution of the scanner, and symbol/reader distance take on the same criticality as with contact readers and one-dimensional bar code. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 5 Two-dimensional barcodes are already being used for concert tickets by sending a barcode to a mobile phone and then scanning the message at the door by a laser gun. In Japan, mobile phones are being adapted to scan two- dimensional barcodes placed in magazines adverts. The barcode is scanned and connects the mobile to the internet and shows the user the film clip or plays the ring tones. Further developments in the lasers used to scan barcodes help improve the efficiency and speed in which barcodes can be scanned. Barcodes can be printed on durable materials and are not affected by substrate materials or electromagnetic emissions, all of which lend them a competitive edge in some industries and environments. Improvements in how barcodes are printed are evolving all the time as manufacturers strengthen the barcode system. Two-dimensional barcodes can be read even when damaged, so this further shortens the gap between the two technologies. Developments in the range at which barcodes can be scanned similarly reduce the apparent performance gap between RFID and bar-coding. It is questionable why there has been no significant research around these developments that can purportedly improve the quality and performance of existing systems. 1.2.6 Advantages of 2-DBarcode systems 2-D codes can store up to 7,089 characters (the 20-character capacity of a one- dimensional barcode). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 6 1.3 Optical character recognition Optical character recognition (OCR) was first used in the 1960s. Special fonts were developed for this application that stylized characters so that they could be read both in the normal way by people and automatically by machines. The most important advantage of OCR systems is the high density of information and the possibility of reading data visually in an emergency (or simply for checking). Today, OCR is used in production, service and administrative fields, and also in banks for the registration of cheques (personal data, such as name and account number, is printed on the bottom line of a cheque in OCR type). However, OCR systems have failed to become universally applicable because of their high price and the complicated readers that they require in comparison with other ID procedures. 1.4 Biometric procedures Biometrics is defined as the science of counting and (body) measurement procedures involving living beings. In the context of identification systems, biometry is the general term for all procedures that identify people by comparing unmistakable and individual physical characteristics. In practice, these are fingerprinting and hand printing procedures, voice identification, less commonly, retina (or iris) identification and, DNA. In order to being able to recognize a person on base of its biometric features, these features first have to be captured, processed and stored as reference sample. The reference template such way formed of the biometric features is stored in a data-base. Figure 1.3: Course of the verification. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 7 1.4.1 Voice identification Recently, specialized systems have become available to identify individuals using speaker verification (speaker recognition). In such systems, the user talks into a micro-phone linked to a computer. This equipment converts the spoken words into digital signals, which are evaluated by the identification software. The objective of speaker verification is to check the supposed identity of the person based upon their voice. This is achieved by checking the speech characteristics of the speaker against an existing reference pattern. If they correspond, then a reaction can be initiated (e.g. ‘open door’). 1.4.2 Fingerprinting procedures Criminology has been using fingerprinting procedures for the identification of criminals since the early twentieth century. This process is based upon the comparison of papillae and dermal ridges of the fingertips, which can be obtained not only from the finger itself, but also from objects that the individual in question has touched. When fingerprinting procedures are used for personal identification, usually for entrance procedures, the fingertip is placed upon a special reader. The system calculates a data record from the pattern it has read and compares this with a stored reference pattern. Modern fingerprint ID systems require less than half a second to recognize and check a fingerprint. In order to prevent violent frauds, fingerprint ID systems have even been developed that can detect whether the finger placed on the reader is that of a living person. 1.4.3 Applications of Biometric procedures Biometric-based solutions are able to provide for confidential financial transactions and personal data privacy. The need for biometrics can be found in federal, state and local governments, in the military, and in commercial applications. Enterprise-wide network security infrastructures, government IDs, secure electronic banking, investing and other financial transactions, retail sales, law enforcement, and health and social services are already benefiting from these technologies. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 8 An example of the reverse side of a typical credit card: Green circle #1 labels the Magnetic stripe 1.4.4 Advantages of Biometric procedures Can provide extremely accurate, secured access to information; fingerprints, retinal and iris scans produce absolutely unique data sets when done. Automated biometric identification can be done very rapidly and uniformly, with a minimum of training. Your identity can be verified without resort to documents that may be stolen, lost or altered. 1.4.5 Disadvantages of Biometric procedures The finger prints of those people working in Chemical industries are often affected. Therefore these companies should not use the finger print mode of authentication. It is found that with age, the voice of a person differs. Also when the person has flu or throat infection the voice changes or if there are too much noise in the environment this method may not authenticate correctly. Therefore this method of verification is not workable all the time. For people affected with diabetes, the eyes get affected resulting in differences. Biometrics is an expensive security solution. 1.5 Magnetic stripe card A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron- based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called swipe card or magstripe, is read by swiping past a magnetic reading head. Magnetic recording on steel tape and wire was invented during World War II for recording audio. In the 1950s, magnetic recording of digital computer data on plastic tape coated with iron oxide was invented. In 1960 IBM used the magnetic tape idea to develop a reliable way of securing magnetic stripes to plastic cards, under a contract with the US government for a security system. A number of International Organization for Standardization standards, ISO/IEC 7810, ISO/IEC 7811, ISO/IEC 7812, ISO/IEC 7813, ISO 8583, and ISO/IEC 4909, now define the physical properties of the card, including size, flexibility, location of the magstripe, magnetic characteristics, and data formats. They also provide the standards for financial cards, including the allocation of card number ranges to different card issuing institutions. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 9 Figure 1.4: Visualization of magnetically stored information on a magnetic stripe card (Recorded with CMOS-MagView). 1.5.1 The magnetic stripe Initially IBM considered and rejected using bar codes and perforations, because these methods did not offer sufficient density of information storage required for the credit cards. Magnetic storage was already known from World War II and computer data storage in the 1950s. The process of attaching a magnetic stripe to a plastic card was invented at IBM in 1960 under a contract with the US government for a security system. There were a number of steps required to convert the magnetic striped media into an industry acceptable device. These steps included: 1) Creating the international standards for stripe record content, including which information, in what format, and using which defining codes. 2) Field testing the proposed device and standards for market acceptance. 3) Developing the manufacturing steps needed to mass produce the large number of cards required. 4) Adding stripe issue and acceptance capabilities to available equipment. These steps were initially managed by Jerome Svigals of the Advanced Systems Division of IBM, Los Gatos, California from 1966 to 1975. In most magnetic stripe cards, the magnetic stripe is contained in a plastic-like film. The magnetic stripe is located 0.223 inches (5.66 mm) from the edge of the card, and is 0.375 inches (9.52 mm) wide. The magnetic stripe contains The first prototype of magnetic stripe card created in IBM in 1960'. A stripe of cellophane magnetic tape is fixed to a piece of cardboard with clear adhesive tape -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 10 three tracks, each 0.110 inches (2.79 mm) wide. Tracks one and three are typically recorded at 210 bits per inch (8.27 bits per mm), while track two typically has a recording density of 75 bits per inch (2.95 bits per mm). Each track can either contain 7-bit alphanumeric characters, or 5-bit numeric characters. Track 1 standards were created by the airlines industry (IATA). Track 2 standards were created by the banking industry (ABA). Track 3 standards were created by the Thrift-Savings industry. Magstripe following these specifications can typically be read by most point- of-sale hardware, which are simply general-purpose computers that can be programmed to perform specific tasks. Examples of cards adhering to these standards include ATM cards, bank cards (credit and debit cards including VISA and MasterCard), gift cards, loyalty cards, driver's licenses, telephone cards, membership cards, electronic benefit transfer cards (e.g. food stamps), and nearly any application in which value or secure information is not stored on the card itself. Many video game and amusement centers now use debit card systems based on magnetic stripe cards. Magnetic stripe cloning can be detected by the implementation of magnetic card reader heads and firmware that can read a signature of magnetic noise permanently embedded in all magnetic stripes during the card production process. This signature can be used in conjunction with common two factor authentication schemes utilized in ATM, debit/retail point-of-sale and prepaid card applications. Counterexamples of cards which intentionally ignore ISO standards include hotel key cards, most subway and bus cards, and some national prepaid calling cards (such as for the country of Cyprus) in which the balance is stored and maintained directly on the stripe and not retrieved from a remote database. 1.5.2 Magnetic stripe coercivity Figure 1.5: Detailed visualization of magnetically stored information on a magnetic stripe card (Recorded with CMOS- MagView). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 11 Magstripes come in two main varieties: high-coercivity (HiCo) at 4000 Oersted and low-coercivity (LoCo) at 300 Oersted but it is not infrequent to have intermediate values at 2750 Oersted. High-coercivity Magstripes are harder to erase, and therefore are appropriate for cards that are frequently used or that need to have a long life. Low-coercivity Magstripes require a lower amount of magnetic energy to record, and hence the card writers are much cheaper than machines which are capable of recording high-coercivity Magstripes. A card reader can read either type of magstripe, and a high-coercivity card writer may write both high and low-coercivity cards (most have two settings, but writing a LoCo card in HiCo may sometimes work), while a low-coercivity card writer may write only low-coercivity cards. In practical terms, usually low coercivity magnetic stripes are a light brown color, and high coercivity stripes are nearly black; exceptions include a proprietary silver-colored formulation on transparent American Express cards. High coercivity stripes are resistant to damage from most magnets likely to be owned by consumers. Low coercivity stripes are easily damaged by even a brief contact with a magnetic purse strap or fastener. Because of this, virtually all bank cards today are encoded on high coercivity stripes despite a slightly higher per-unit cost. Magnetic stripe cards are used in very high volumes in the mass transit sector, replacing paper based tickets with either a directly applied magnetic slurry or hot foil stripe. Slurry applied stripes are generally less expensive to produce and are less resilient but are suitable for cards meant to be disposed after a few uses. 1.5.3 How does a magnetic stripe on the back of a credit card work? The stripe on the back of a credit card is a magnetic stripe, often called a magstripe. The magstripe is made up of tiny iron-based magnetic particles in a plastic-like film. Each particle is really a very tiny bar magnet about 20 millionths of an inch long. The magstripe can be "written" because the tiny bar magnets can be magnetized in either a north or South Pole direction. The magstripe on the back of the card is very similar to a piece of cassette tape fastened to the back of a card. Instead of motors moving the tape so it can be read, your hands provides the motion as you "swipe" a credit card through a reader or insert it in a reader at the gas station pump. Your card also has a magstripe on the back and a place for your all-important signature. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 12 1.6 Smart cards A smart card is an electronic data storage system, possibly with additional computing capacity (microprocessor card), which for convenience is incorporated into a plastic card the size of a credit card. The first smart cards in the form of prepaid telephone smart cards were launched in 1984. Smart cards are placed in a reader, which makes a galvanic connection to the contact surfaces of the smart card using contact springs. The smart card is supplied with energy and a clock pulse from the reader via the contact surfaces. Data transfer between the reader and the card takes place using a bidirectional serial interface (I/O port). It is possible to differentiate between two basic types of smart card based upon their internal functionality: the memory card and the microprocessor card. One of the primary advantages of the smart card is the fact that the data stored on it can be protected against undesired (read) access and manipulation. Smart cards make all services that relate to information or financial transactions simpler, safer and cheaper. For this reason, 200 million smart cards were issued worldwide in 1992. In1995 this figure had risen to 600 million, of which 500 million were memory cards and100 million were microprocessor cards. The smart card market therefore represents one of the fastest growing subsectors of the microelectronics industry. One disadvantage of contact-based smart cards is the vulnerability of the contacts to wear, corrosion and dirt. Readers that are used frequently are expensive to maintain due to their tendency to malfunction. In addition, readers that are accessible to the public (telephone boxes) cannot be protected against vandalism. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 13 1.6.1 Memory cards In memory cards the memory, usually an EEPROM, is accessed using a sequential logic (state machine). It is also possible to incorporate simple security algorithms, e.g. stream ciphering, using this system. The functionality of the memory card in question is usually optimized for a specific application. Flexibility of application is highly limited but, on the positive side, memory cards are very cost effective. For this reason, memory cards are predominantly used in price sensitive, large-scale applications. One example of this is the national insurance card used by the state pension system in Germany. 1.6.2 Microprocessor cards As the name suggests, microprocessor cards contain a microprocessor, which is connected to a segmented memory (ROM, RAM and EEPROM segments). The mask programmed ROM incorporates an operating system (higher program code) for the microprocessor and is inserted during chip manufacture. The contents of the ROM are determined during manufacturing, are identical for all microchips from the same production batch, and cannot be overwritten. The chip’s EEPROM contains application data and application-related program code. Reading from or writing to this memory area is controlled by the operating system. The RAM is the microprocessor’s temporary working memory. Data stored in the RAM are lost when the supply voltage is disconnected (Figure 1.6). Microprocessor cards are very flexible. In modern smart card systems it is also possible to integrate different applications in a single card (multi-application). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 14 The application-specific parts of the program are not loaded into the EEPROM until after manufacture and can be initiated via the operating system. Microprocessor cards are primarily used insecurity sensitive applications. Examples are smart cards for GSM mobile phones and the new EC (electronic cash) cards. The option of programming the microprocessor cards also facilitates rapid adaptation to new applications. 1.7 Electronic Article Surveillance (EAS) EAS are typically a one bit system used to sense the presence/absence of an item. The large use for this technology is in retail stores where each item is tagged and large antenna readers are placed at each exit of the store to detect unauthorized removal of the item (theft). These systems were the first form of RFID to be commercially available and have been in use since the 1960’s. Figure 1.6: Operating principle of the EAS radio frequency procedure. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 1Auto-ID systems ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬ P a g e | 1 - 15 -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-1 2 HISTORY OF RFID 2.1 It All Started with IFF By the 1930s, the primitive biplanes of fabric and wood that had populated the skies above the battlefields of World War I had become all-metal monoplanes capable of carrying thousands of kilograms of explosives and traveling at hundreds of kilometers per hour: by the time observers could visually identify an incoming flight, it was too late to respond. Detection of airplanes beyond visual range was the task of microwave radar, also under rapid development in the 30s, but mere detection of the presence of aircraft begged the key question: whose side were they on? It was exactly this inability to identify aircraft that enabled the mistaken assignment of incoming Japanese aircraft to an unrelated United States bomber flight and so ensured surprise at Pearl Harbor in 1941. The problem of identifying as well as detecting potentially hostile aircraft challenged all combatants during World War II. The Luftwaffe, the German air force, solved this problem initially using an ingeniously simplemaneuver1. During engagements with German pilots at the beginning of the war, the British noted that squadrons of fighters would suddenly and simultaneously execute a roll for no apparent reason. This curious behavior was eventually correlated with the interception of radio signals from the ground. It became apparent that the Luftwaffe pilots, when they received indication that they were being illuminated by their radar, would roll in order to change the backscattered signal reflected from their airplanes (Figure 2.1). The consequent modulation of the blips on the radar screen allowed the German radar operators to identify these blips as friendly targets. This is the first known example of the use of a passive backscatter radio link for identification, a major topic of the remainder of this book. Passive refers to the lack of a radio transmitter on the object being identified; the signal used to communicate is a radio signal transmitted by the radar station and scattered back to it by the object to be identified (in this case an airplane). As a means of separating friend from foe, rolling an airplane was of limited utility: aircraft can be rolled and no specific identifying information is provided. That is, the system has problems with security and the size of the ID space (1 bit in this case). More capable means of establishing the identity of radar targets were the subject of active investigation during the 1930s. The United States and Britain tested simple IFF systems using an active beacon on the airplane (the XAE and Mark I, respectively) in 1937/1938. The Mark III system, widely used by the Britain, the United States, and the Soviet Union -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-2 during the war, used a mechanically tunable receiver and transmitter with six possible identifying codes(i.e., the ID space had grown to 2.5 bits). By the mid- 1950s, the radar transponder still in general use in aviation today had arisen. Modern transponders are interrogated by a pair of pulses at 1030 MHz, in the ultra-high frequency (UHF) band about which we will have a lot more to say shortly. The transponder replies at 1090 MHz with 12 pulses each containing1 bit of information, providing an ID space of 4096 possible codes. A mode C transponders connected to the aircraft altimeter and also returns the current altitude of the aircraft. A mode-S transponder also allows messages to be sent to the transponder and displayed for the pilot. Finally, the typical distance between the aircraft and the radar is on the order of one to a few kilometers. Since it takes light about 3μs to travel 1 km, the radar reflection from a target is substantially delayed relative to the transmitted pulse, and that delay can be used to estimate the distance of the object. An aircraft transponder thus provides a number of functions of considerable relevance to all our discussions in this book: • Identification of an object using a radio signal without visual contact or clear line of sight: radio-frequency identification. • An ID space big enough to allow unique identification of the object. • Linkage to a sensor to provide information about the state of the object identified (in this case, the altitude above ground). • Location of each object identified (angle and distance from the antenna). • Transmission of relevant information from the interrogator to the transponder. These functions encompass the basic requirements of most RFID systems today: RFID has been around for a long time. However, for many years, wider application of these ideas beyond aircraft IFF was limited by the cost and size of the equipment required. The early military transponders barely fit into the confined cabins of fighter airplanes, and even modern general aviation transponders cost US$1000–5000. In order to use radio signals to identify smaller, less-expensive objects than airplanes, it was necessary to reduce the size, complexity, and cost of the mechanism providing the identification. The number of companies actively involved in the development and sale of RFID systems indicates that this is a market that should be taken seriously. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-3 Whereas global sales of RFID systems were approximately 900 million $US in the year 2000 it is estimated that this figure will reach 2650 million $US in 2005 (Krebs, n.d.). Figure 2.1: The Use of Backscattered Radiation to Communicate with a Radar Operator (not to scale!). Furthermore, in recent years contactless identification has been developing into an independent interdisciplinary field, which no longer fits into any of the conventional pigeon holes. It brings together elements from extremely varied fields: HF technology and EMC, semiconductor technology, data protection and cryptography, telecommunications, manufacturing technology and many related areas. 2.2 RFID TECHNOLOGY Radio frequency identification (RFID) tags are poised to replace barcodes as the tags of choice, but the replacement has been slow because of the inability to bring tag cost down to 5 cent (US). While silicon die costs have been lowered via die reduction, assembly cost for small dies need to be lowered concomitantly. Although large-scale low cost tag assembly solutions have been developed, they are not suited for adoption by conventional packaging house because of their high capital investment. In this thesis, a low cost hybrid self- alignment die assembly method suited for evolutionary migration was developed. In this approach, small dies are firstly placed onto the substrate using low cost robotic pick and place and fine self-align to nanometer accuracy using low surface tension adhesive. Design guidelines on the usage of adhesive liquid volume and oversized binding sites were developed. Tag antenna manufacturing is another major cost -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-4 factor. Coil antenna fabricated by printing conductive ink on plastic substrates are recognized to be lower in assembly cost, but are lower in tag readability and read range reproducibility. The effects of material, antenna line geometry, and tag configuration on read range were examined in this study. Tag design and selection criteria that can compensate for bent tag on cylindrical bottles or soft packages were developed. Experimental characterization of the tag behavior revealed the presence of an antenna geometry-independent read range plateau. Tags designed to function in the plateau regime enable the use of low precision high volume printing techniques as fabrication processes to lower tag fabrication cost, without sacrificing read range consistency. Tag performance can be further increased using thick lined printed antennas and line compaction to reduce line resistance. Tags fabricated using these new developed design and fabrication methods were shown to have read ranges comparable to tags with metal wire antennas. Innovations on self-alignment die assembly and printed coil design made the production scaling to high volume and low cost possible. The die assembly cost can potentially be brought down to 0.25 cent (US) using hybrid self-alignment at high volume. The printed antenna cost, with the compaction process, can be reduced down to 1 cent (US). Using this new compacted printed antenna designed according to the developed design guidelines and the demonstrated hybrid die assembly technique developed in this thesis, the total manufacturing cost of a tag is estimated to be 2.49 cent (US). The tag cost is below the 5 cent (US) threshold tag cost such that the developed technologies can be adopted as a low cost foundation for wide adoption of RFID in the marketplace. 2.3 Components of an RFID System  The transponder, which is located on the object to be identified;  The interrogator or reader, which, depending upon the design and the technology used, may be a read or write/read device(in accordance with normal colloquial usage the data capture device is always referred to as the reader, regardless of whether it can only read data or is also capable of writing). A practical example is shown in Figure 2.2. A reader typically contains a radio frequency module (transmitter and receiver), a control unit and a coupling element to the transponder. In addition, many readers are fitted with an additional interface (RS 232, RS 485, etc.) to enable them to forward the data received to another system (PC, robot control system, etc.). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-5 The transponder, which represents the actual data-carrying device of an RFID system, normally consists of a coupling element and an electronic microchip. Figure 2.2: An RFID system is always made up of two components. 2.4 Basic Operation The reader, sometimes called an interrogator or scanner, sends and receives RF data to and from the tag via antennas. A reader may have multiple antennas that are responsible for sending and receiving radio waves. The data acquired by the readers is then passed to a host computer, which may run specialist RFID software or middleware to filter the data and route it to the correct application, to be processed into useful information. 2.5 Different Types of RFID There are several versions of RFID that operate at different radio frequencies. Three primary 2.5.1 Frequency bands are being used for RFID:  Low Frequency (125/134 KHz)Most commonly used for access control, animal tracking and asset tracking.  High Frequency (13.56 MHz)Used where medium data rate and read ranges up to about 1.5 meters are acceptable. This frequency also has the -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-6 advantage of not being susceptible to interference from the presence of water or metals.  Ultra High-Frequency (850 MHz to 950 MHz)Offer the longest read ranges of up to approximately 3 meters and high reading speeds. Applications for RFID within the supply chain can be found at multiple frequencies and different RFID solutions may be required to meet the varying needs of the marketplace. Since UHF (Ultra High Frequency) has the range to cover portals and dock-doors it is gaining industry support as the choice frequency for inventory tracking applications including pallets and cases. 2.5.2 RFID tags are further broken down into two categories: (a) Active RFID Tags are battery powered. They broadcast a signal to the reader and can transmit over the greatest distances (>100 meters). They can be used to track high value goods like vehicles and large containers of goods. Shipboard containers are a good example of an active RFID tag application. (b) Passive RFID Tags do not contain a battery. Instead, they draw their power from the radio wave transmitted by the reader. The reader transmits a low power radio signal through its antenna to the tag, which in turn receives it through its own antenna to power the integrated circuit (chip). The tag will briefly converse with the reader for verification and the exchange of data. As a result, passive tags can transmit information over shorter distances (typically 3 meters or less) than active tags. They have a smaller memory capacity and are considerably lower in cost making them and ideal for tracking lower cost items. 2.5.3 There are two basic types of chips available on RFID tags, Read-Only &Read-Write: Read only chips:are programmed with unique information stored on them during the manufacturing process often referred to as a “number plate” application. o The information on read-only chips cannot be changed. Read-Write chips:the user can add information to the tag or write over existing information when the tag is within range of the reader. o Read-Write chips are more expensive than Read Only chips. Applications for these may include field service maintenance or “item attendant data” where a maintenance record associated with a mechanical component is stored and updated on a tag attached to the component. Another method used is called a "WORM" chip (Write Once Read Many). It can be written once and then becomes "Read only". -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-7 2.6 Advantages of the Technology The advantages of RFID can be broadly classified into the following two types:  Current:These advantages are immediately realizable with the technology products that exist today.  Future:These advantages are either available in some form today or will be available as improved features in the future as the technology matures. These are not official terminologies, but are used for the sake of convenience and to aid in better understanding of a benefit. The following list covers both of these advantage types, and the rest of this chapter describes how much benefit is available today versus how much will be available in the future: 1. Contactless. An RFID tag can be read without any physical contact between the tag and the reader. 2. Writable data. The data of a read-write (RW) RFID tag can be rewritten a large number of times. 3. Absence of line of sight. A line of sight is generally not required for an RFID reader to read an RFID tag. 4. Variety of read ranges. An RFID tag can have a read ranges as small as few inches to as large as more than 100 feet. 5. Wide data-capacity range. An RFID tag can store from a few bytes of data to virtually any amount of data. 6. Support for multiple tag reads. It is possible to use an RFID reader to automatically read several RFID tags in its read zone within a short period of time. 7. Rugged. RFID tags can sustain rough operational environment conditions to a fair extent. 8. Perform smart tasks. Besides being a carrier and transmitter of data, an RFID tag can be designed to perform other duties (for example, measuring its surrounding conditions, such as temperature and pressure). The following, although often touted as a benefit of RFID, is not considered an advantage:  Extreme read accuracy: RFID is 100 percent accurate. The following sections discuss the previously listed advantages in detail. 2.6.1 Contactless An RFID tag does not need to establish physical contact with the reader to transmit its data, which proves advantageous from the following perspectives: -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-8  No wear and tear.Absence of physical contact means there is no wear and tear on the readers as well as on the tags for reading and writing data.  No slowing down of operations.Existing operations do not have to slow down to bear the extra overhead of bringing a reader physically into contact with a tag. Establishing such a physical contact can sometimes prove impossible. In a scenario in which tagged cases of items are moving at a rapid speed on a conveyer belt, there is a high chance that a reader will fail to maintain a physical contact with such a moving box, resulting in a missed tag read. As a result, had RFID been contact-based, it could not have been applied satisfactorily in a large number of business applications (such as supply-chain applications and so on).  Automatic reading of several tags in a short period of time.Had RFID been contact-based, the number of tags read by a reader would have been limited by the number of tags it could touch at a particular time. To increase this number, the reader's physical dimensions need to be increased, resulting in a higher-cost, clumsy reader. 2.6.2 Writable Data RW RFID tags that are currently available can be rewritten from 10,000 times to 100,000 times or more! Although the use of these types of tags is currently limited compared to write once, read many (WORM) tags, you can use these tags in custom applications where, for example, time-stamped data about the tagged object might need to be stored on the tag locally. This guarantees that the data will be available even in absence of a back-end connection. In addition, if a tag (that is currently attached to an object) can be recycled, the original tag data can be overwritten with new data, thus allowing the tag to be reused. Although writable tags might seem like an advantage, they are not widely used today because of the following reasons:  Business justification of tag recycling. Virtually all business cases that involve tag recycling impact business operations. For example, the following must be factored in: how tags are going to be collected from the existing objects, when they are going to be collected, how these are going to be re-introduced to the operations, additional resources and overhead required, and so on. Unless the tag is active or semi-active and is expensive, in most situations, generally, tag recycling does not make business sense.  Security issue. How can tags safeguard accidental and malicious overwriting of data by valid and rogue readers when in use? If the application is used outside an enterprise in an uncontrolled environment, the security implications multiply many times. Even if such a tag is used -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-9 within the four walls of an enterprise, the issue of security remains. To satisfactorily address this issue, additional hardware, setup, and processes might be necessary; this, in turn, can result in high implementation costs that might prove unjustifiable. Currently, it seems as if RW tags will continue to be used within the specific secure bounds of an enterprise.  Necessity of dynamic writes. If most of the RW tag applications are going to be used mainly inside the four walls of an enterprise, there is a high degree of probability of the presence of a network and the ability to access the back-end system through this network. Therefore, using the unique tag ID, the back end can store the data without any need to write this data on the tag itself. Also, process changes can be made to handle exceptional conditions when the network is down for example, generally critical manufacturing facilities have two modes of operation, one automatic and one manual so that if the automatic mode of operation fails, the operators can switch to the manual mode without stopping production lines.  Slower operating speed. A tag write is often slower than a tag read operation. Therefore, an application that does tag rewrites has a good possibility of being slower compared to an application that does tag reads only. These issues might seem daunting to the reader. However, it is certainly possible that some RFID applications exist for which using RW tags makes good business as well as technical sense. An example of such an application is monitoring the production quality control of a bottling operation for a medical drug. First, RW RFID tags are attached to empty bottles, which are then washed in hot water and sanitizing solutions, dried, and subsequently go through a series of steps before the drug is placed in these bottles and sealed. It is assumed that the tags are sturdy enough to withstand the various processing steps. At each processing step, the parameters of the process such as temperature, humidity, and so on are written to the tags. When the sealed bottles roll off the assembly line, their associated tag data is automatically read by quality control systems. This way, any processing step that fell short of the minimum requirements can be discovered, and the overall quality of the bottling process can be quantized. 2.6.3 Absence of Line of Sight The absence of line of sight is probably the most distinguishing feature of RFID. An RFID reader can read a tag through obstructing materials that are RF-lucent for the frequency used. For example, if a tag is placed inside a cardboard box, a reader operating in UHF can read this tag even if this box is -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-10 sealed on all the sides! This capacity proves useful for inspecting the content of a container without opening it. This feature of RFID has privacy rights infringement implications, however. If a person is carrying some tagged items in a bag, an RFID reader can (potentially) read the tagged item data without this person's consent. If this person's personal information is associated with the tagged item data (at the point of sale by the merchant, for example), it might be possible to access this information (using a suitable application) without the person's consent or knowledge, which might constitute a privacy rights infringement. To prevent this, a reader should not read these tags after sale is completed unless explicitly needed or authorized by the buyer. There are multiple ways to achieve this objective Note that in some situations, a line of sight is needed to help configure the tag read distance, reader energy, and reader antenna to counter the environmental impact. These situations involve UHF tags and the presence of a large amount of RF-reflecting materials, such as metal, in the operating environment giving rise to multipath. For example, consider a machinery tool production line where virtually everything is made of metal. A large amount of RF energy from the readers installed in this environment gets reflected from the objects in the environment. In this case, to achieve a good read accuracy, a tag and a reader must be placed so that there is no obstacle between them.This is a current advantage of RFID. It is possible that future improvements in the technology can bypass some of the hurdles faced by the presence of RF-opaque materials between the reader and the tag. Therefore, this is a future benefit, too. 2.6.4 Variety of Read Ranges A low-frequency (LF) passive RFID tag generally has a read distance of a few inches; for a passive high-frequency (HF) tag, this distance is about 3 feet. The reading distance of an ultra-high-frequency (UHF) passive tag is about 30 feet. A UHF (for example, 433 MHz) active tag can be read at a distance of 300 feet and an active tag in the gigahertz range can have a reading distance of more than 100 feet. These reading distances are usually realized under ideal conditions. Therefore, the actual tag-reading distance of a real-world RFID system can be substantially less than these numbers. For example, the reading distance of 13.56 MHz tags in general do not exceed a few inches. This wide array of reading distances makes it possible to apply RFID to a wide variety of applications. Whereas the LF read distance passive tags are ideally suited for security, personnel identification, and electronic payments, to name a few, you can use HF passive tags for smart-shelf applications; passive UHF for supply- -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-11 chain applications, tracking, and many other types of applications; and, finally, you can use passive tags in the microwave ranges for anti-counterfeiting. You can use active and semi-active tags in these frequency ranges for tracking, electronics toll payment, and almost limitless other possibilities. As you can understand, RFID has virtually an unlimited spectrum of current and possible applications. Today, the tags for every frequency type are commercially available. In addition, the location of an active or a passive tag can be associated with a reader that reads this tag. Therefore, if a reader installed at a certain dock door of a warehouse reads a tag in its read zone, the location of this tag can be assumed to be this dock door at the time of reading. This location information can then be made available through a private or public (for example, Internet) network over a wide geographical area. As a result, the tag can be tracked thousands of miles away from its actual location. Future improvements of the technology will have limited impact on this aspect because the entire range of reading distances is currently available using direct (that is, a reader) and indirect (that is, a network) means. Hence, this feature is a current advantage of RFID. 2.6.5 Wide Data-Capacity Range A typical passive tag can contain a few bits to hundreds of bits for data storage. Some passive tags can carry even more data. For example, the ME- Y2000 series (also known as coil-on chip) passive, RW miniature tag from Maxell operating in the 13.56 MHz range can carry up to 4 K bytes of data within its 2.5 mm x 2.5 mm space. An active tag has no theoretical data-storage limit because the physical dimensions and capabilities of an active tag are not limited, provided this tag is deployable. There are two approaches to use an RFID tag for an application. The first one stores only a unique identification number on the tag, analogous to a "license plate" of an automobile that uniquely identifies the tagged item; the second one stores both a unique identification number and data related to the tagged object. A large number of unique identifiers can be generated with a relatively small number of bits. For example, using 96 bits, a total of 80,000 trillion trillion unique identifiers can be generated so, a relatively small number of bits are sufficient to tag virtually any type of object in the world. However, some applications might choose to store additional data on a tag locally. The advantage of storing this data locally is that no access to a networked database is required to retrieve the object data using its unique identifier as a key, an -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-12 advantage that proves useful if the tagged object is going to be moved around in areas where the presence of network access to an object database is either not available or undesirable. Even when such a network connection is available, the associated application is such that it must not be impacted by a network outage or delay. Therefore, one of the benefits of storing data locally on the tags is that the resulting application can be made largely independent of a back-end system. However, such a scheme has drawbacks compared to a "license plate" type of approach. First, data security needs to be addressed so that tag data can neither be accidentally overwritten by a valid reader nor by a rogue reader intentionally. The transmission time necessary for a high data capacity tag to transmit all its data bits correctly to a reader can be several times more compared to just transmitting the unique identifier. In addition, an increase in data transmission leads to an increase in error rate of transmission. A high memory capacity tag will be more expensive than the tags that can store only a unique identifier. Therefore, just because it is available, using a high memory capacity tag in an application does not seem like a good idea unless the application specifically demands it (especially true for applications that have a hard time limit to perform a specific task). An active tag, however, can use a large data-storage capacity to support its custom tasks. A small amount of which, most probably containing the results of these tasks, might end up getting transmitted by this tag (which is perfectly acceptable because this data is dynamic and can only be determined by the tag itself by scanning its environment 2.6.6 Support for Multiple Tag Reads Support for multiple tag reads ranks as one of the most important benefits of RFID. Using what is called an anti-collision algorithm, an RFID reader can automatically read several tags in its read zone in a short period of time. Generally, using this scheme a reader can uniquely identify a few to several tags per second depending on the tag and the application. This benefit allows the data from a collection of tagged objects, whether stationary or in motion (within the reader limits), to be read by a reader, thus obviating any need to read one tag at a time. Consider, for example, one of the classic tasks of a financial institution: counting a stack of currency notes to determine its total count and value. Assuming these notes have proper RFID tags, the data from these currency tags can be read using an RFID reader, which can then be used to determine the total count and the value of the notes in aggregate in a very short period of time, automatically. This method is much more efficient compared to the traditional counting techniques. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-13 Now consider another classic example: loading a truck with cases of merchandise at a shipping dock and receiving it at a receiving dock. Currently, for these types of applications, either the boxes are not inventoried at all during shipping time (they are, however, inventoried most of the time at the receiving dock) or they are inventoried using bar codes (which is manual and time- consuming). As a result, business might lose a considerable amount of inventory annually due to shrinkage or incur a high recurrent overhead in the cost of labor. If RFID tags can be applied to the boxes before they are shipped, a stationary reader placed near a loading truck can read all the boxes, automatically, when these boxes are being loaded into this truck. Thus, the business can have an accurate list of items being shipped to a distributor or a retailer. In addition, significant labor costs were saved by eliminating manual scanning of the labels, which would have been unavoidable if a technology such as bar code had been used instead. The data collected from these tags can be checked against the actual order to verify whether a box should be loaded into this truck (thus reducing the number of invalid shipments). As you can understand, this particular RFID advantage can speed up and streamline existing business operations considerably. Contrary to popular belief, a reader can communicate with only one tag in its read zone at a time. If more than one tag attempts to communicate to the reader at the same time, a tag collision occurs. A reader has to resolve this collision to properly identify all the tags in its read zone. Therefore, a reader imposes rules on communication so that only one tag can communicate to the reader at a time, during which period the other tags must remain silent. This is what constitutes an anti-collision algorithm Note that there is a difference between reading a tag's data in response to an anti-collision command versus reading a tag's data completely. In the former case, only certain data bits of a tag are read; whereas in the latter, the complete set of data bits of a particular tag are read. In addition, there is a theoretical as well as practical limitation on how many tags can be identified by a reader within a certain period of time. 2.6.7 Rugged A passive RFID tag has few moving parts and can therefore be made to withstand environmental conditions such as heat, humidity, corrosive chemicals, mechanical vibration, and shock (to a fair degree). For example, some passive tags can survive temperatures ranging from 40°F to 400°F (40° C to 204°C). Generally, these tags are made depending on the operating environment of a specific application. Today, no single tag can withstand all these environmental conditions. An active and semi-active tag that has on- -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-14 board electronics with a battery is generally more susceptible to damage compared to a passive tag. A tag's ruggedness almost always increases its price. This is a current benefit because tags with a variety of resistance to operating environments are available. However, plenty of room exists for improvement, and as the tag technology improves, it is expected that more tags will be available that can better resist harsh environments than their present-day counterparts. Therefore, this can also be called a future benefit. 2.6.8 Perform Smart Tasks The on-board electronics and power supply of an active tag can be used to perform specialized tasks such as monitoring its surrounding environment (for example, detecting motion). The tag can then use this data to dynamically determine other parameters and transmit this data to an available reader. For example, suppose that an active tag is attached to a high-value item for theft detection. Assume that this active tag has a built-in motion sensor. If someone attempts to move the asset, the tag senses movement and starts broadcasting this event into its surroundings. A reader can receive this information and forward the information to a theft- detection application, which in turn can sound an alarm to alert the personnel. It might seem that by just taking off the tag from the asset and then putting the tag back where it was (while taking the asset away) would fool the tag into thinking that the asset is stationary again. However, it is possible for such a tag to sense that it is no longer attached to the asset. The tag can then send another type of broadcast message to signify this event. 2.6.9 Read Accuracy In the media, the read accuracy of RFID is mentioned variously as "very accurate," "100 percent accurate," and so on, but no objective study shows how accurate RFID reads really are. It would definitely be desirable to back up such accuracy statements with hard data, because no technology can offer 100 percent read accuracy in every operating environment all the time. Factors on which RFID read accuracy depends include the following:  Tag type. Which frequency tags are being used, the tag antenna design, and so on can have a bearing on the read accuracy of an RFID system.  Tagged object. The composition of the object, how it is packed, the packing material, and so on play important roles in determining the readability and hence the read accuracy. Also note that impact of this factor depends on the frequency of the RFID system used.  Operating environment. Interference from existing mobile equipment, electrostatic discharge (ESD), the presence of metal and liquid bodies, among other factors, can pose a problem for read accuracy in the UHF and microwave frequencies. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-15  Consistency. Tag orientation and placement relative to the reader antennas can significantly impact read accuracy. Another issue with RFID is what are called phantom reads or false reads. In this situation, a random but seemingly valid tag data is recorded by the reader for a brief period of time. After this time, the tag data can no longer be read by the reader! The problem arises when a reader receives incorrect data from a tag, which might happen for various reasons (such as a poorly constructed error- correcting protocol). Phantom reads are "bugs" in the supplier system. Incorrect installations might also give rise to this phenomenon. In general, phantom reads are not an issue. However, this shows that the objective determination of RFID accuracy is not easy, that it depends on several factors. It is possible for the accuracy rates of two identical RFID systems used in different environments to differ. It might not always be possible to increase the read accuracy and degree of automation of highly automated systems that are in existence today. This is a current benefit because several applications generally do showsufficient accuracy to meet business requirements. However, the read accuracy of RFID has good potential to improve as improved tags, readers, and antennas become available in the future. Therefore, this can also be called a future benefit. 2.7 Disadvantages of the technology 1. Poor performance with RF-opaque and RF-absorbent objects. This is a frequency-dependent behavior. The current technology does not work well with these materials and, in some cases, fail completely. 2. Impacted by environmental factors. Surrounding conditions can greatly impact RFID solutions. 3. Limitation on actual tag reads. A practical limit applies as to how many tags can be read within a particular time. 4. Impacted by hardware interference. An RFID solution can be negatively impacted if the hardware setup (for example, antenna placement and orientation) is not done properly. 5. Limited penetrating power of the RF energy. Although RFID does not need line of sight, there is a limit as to how deep the RF energy can reach, even though RF-lucent objects. 6. Immature technology. Although it is good news that the RFID technology is undergoing rapid changes, those changes can spell inconvenience for the unwary. The remainder of this chapter discusses these limitations in detail. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-16 2.7.1 Poor Performance with RF-Opaque and RF- Absorbent Objects If high UHF and microwave frequencies are used, and if the tagged object is made of RF-opaque material such as metal, some type of RF-absorbent material such as water, or if the object is packaged inside such RF-opaque material, an RFID reader might partially or completely fail to read the tag data. Custom tags are available that alleviate some of the read problems for particular types of RF-opaque and RF-absorbent materials. In addition, packaging can present problems if made of RF-opaque materials such as metal foils. It is expected that improvement in the tag technology will overcome several of the current problems associated with RF-opaque/RF-absorbent objects. 2.7.2 Impacted by Environmental Factors If the operations environment has large amounts of metal, liquids, and so on, those might affect the read accuracy of the tags, depending on the frequency. The reflection of reader antenna signals on RF-opaque objects causes what is known as multipath. It is a safe bet in these types of environments to provide a direct line of sight to the tags from a reader. Although the tag reading distance, reader energy, and reader antenna configuration are the major parameters that need to be configured in these cases to counter the environmental impact, a line of sight helps to achieve this configuration. In some cases, however, this might not be possible (for example, in an operating environment where there is high human traffic). A human body contains a large amount of water, which is RF-absorbent at high UHF and microwave frequencies. Therefore, when a person is in between a tag and a reader, there is a good possibility that this reader cannot read the tag before this person moves away. So, serious degradation of system performance might result. In addition, the existence of almost any type of wireless network within the operating environment can interfere with the reader operation. Electric motors and motor controllers can also act as a source of noise that can impact a reader's performance. Some older wireless LANs (WLANs) in the 900 MHz range can interfere with the readers. This problem mostly exists in older facilities that have not upgraded their WLAN equipment. 2.7.3 Limitations on Actual Tag Reads The number of tags that a reader can identify uniquely per unit time (for example, per second) is limited. For example, today, a reader on average can uniquely identify a few to several tags per second. To achieve this number, this reader has to read tags' responses several hundred times a second. Why? Because the reader has to employ some kind of anti-collision algorithm to -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-17 identify these tags; to identify a single tag, a reader has to walk down the range of possible values. Therefore, several readings of tag responses are required before a reader can uniquely determine tag data. A limit applies as to how many such reads a reader can perform within a unit time, which, in turn, dictates a limit on the number of unique tags that can be identified within this same time period. Improvement in the reader technology will undoubtedly increase the number of tags that can be uniquely identified per unit time, but there will always be an ultimate limit on this number that no reader will be able to exceed. 2.7.4 Impacted by Hardware Interference RFID readers can exhibit reader collisionif improperly installed. A reader collision happens when the coverage areas of two readers overlap and the signal of one reader interferes with the other in this common coverage area. This issue must be taken into account when an RFID installation plan is worked out. Otherwise, degradation of system performance might take place. This issue can be somewhat solved today by using what is known as time division multiple access (TDMA). This technique instructs each reader to read at different times rather than both reading at the same time. As a result, two readers interfere with one another no longer. However, a tag in the overlapping area of these two readers might be read twice. Therefore, the RFID application must have an intelligent filtering mechanism to eliminate duplicate tag reads. As RFID technology improves, new solutions to this issue might become available. 2.7.5 Limited Penetrating Power of the RF Energy The penetrating power of RF energy finally depends on the transmitter power of the reader and duty cycle, which are regulated in several countries around the world. For example, a reader might fail to read some cases on a pallet if they are stacked too deep, even if these cases are all made of RF-lucent material for the frequency used. How many such cases can be put on a pallet for proper reading? You can only determine the answer to this question by experimenting with actual boxes stacked on an actual pallet in the actual operating environment using actual RFID hardware. This number will also vary from country to country, depending on the restriction of reader power and duty cycle. Therefore, the answer needs to be determined experimentally; it is very difficult, if not impossible, to determine it theoretically. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-18 Unfortunately, this limitation will remain as long as international restrictions on reader power and duty cycle remain. Therefore, if you need to deploy a solution in multiple countries, you must seriously consider this issue. 2.7.6 Immature Technology Immature technology is a practical issue facing RFID technology today. An RFID solution can only be as good as the hardware currently available from the vendors. The vendors are doing their best to develop improved products, but maturity might not be available for some time to come. For example, it is not uncommon for passive UHF tags currently used in supply-chain operations to get damaged when subjected to existing handling techniques, with the defective tag rates shooting up as high as 20 percent or more. The same tag types (for example, passive 915 MHz for metal) from different vendors might perform differently. It is possible that a tag needed for satisfactory read accuracy for a specific application is not currently available, despite intensive research being conducted both at the theoretical (for example, antenna design) and manufacturing (for example, material used, processing techniques) levels to build tags of different kinds. Building a custom tag for an application can be very expensive (typically in the range of $100,000). Readers have come a long way in the past two years, gradually transitioning from a simple interrogator to a well-defined network device with built-in intelligence to support several functions needed by an RFID application. Some of these functions are filtering, caching recent tag reads, input from external sensors, output for activating sensors and actuators, and so on. Similarly, antenna technology is making antennas smaller and cheaper. However, a side effect of these improvements is that new RFID hardware is coming out at a very fast rate, which might urge businesses to upgrade their equipment at the same rate! Such rapid upgrades are generally not necessary because the products are backward compatible in most cases. Business has to implement realistic strategies so that its current investment in RFID hardware is not wasted as new products come out. The issue of immaturity/maturity will continue to be part of RFID technology in the near future. Stabilization of the technology in terms of products and globally acceptable standards will eradicate this issue, but a prediction of the timeline for such stabilization is difficult to make. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-19 2.8 Applications RFID tags are becoming so ubiquitous in our society that the average person probably encounters them daily without realizing it. Did you go to the bookstore today? The book you purchased was probably inventoried using RFID technology. Have you traveled overseas recently? The government tracks travel data using RFID chips in passports. Have you ever had trouble finding a lost pet? Maybe you should consider having an RFID tag implanted in Fluffy to help track her next time she gets lost! By providing a cheap, efficient, and reliable way to collect and store data, RFID offers limitless possibilities for current and future use. The list below highlights just a few of the myriad uses of RFID technology:  Product Tracking – RFID tags are increasingly used as a cost- effective way to track inventory and as a substitute for barcodes. For instance, bookstores such as Barnes & Noble use RFID to identify books to be removed from shelves and returned to publishing houses.  Toll Road Payments – Highway toll payment systems, such as E- Z Pass in the eastern states, uses RFID technology to electronically collect tolls from passing cars. Instead of stopping at the toll booth, cars pass directly through in the E- Z Pass lane and the toll is automatically deducted from a pre-paid card.  Passports – A number of countries, including Japan, the United States, Norway, and Spain incorporate RFID tags into passports to store information (such as a photograph) about the passport holder and to track visitors entering and exiting the country.  Identification – RFID chips can be implanted into animals and people to track their movements, provide access to secure locations, or help find lost pets. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-20  Libraries – Libraries use RFID tags in books and other materials to track circulation and inventory, store product information (such as titles and authors), and to provide security from theft. Because RFID tags can be scanned without physically touching the item, checking books in and out, plus doing laborious tasks such as shelf inventory, can be accomplished quickly and efficiently using RFID technology.  Shipping – Large shipments of materials, such as retail goods, often utilize RFID tags to identify location, contents, and movement of goods. Walmart is one of the largest consumers of this technology to assist in tracking shipments of merchandise  Other uses – RFID tags are employed in numerous other ways, including implantation in Saguaro cacti to discourage black-market traders, placement in car tires to transmit road condition information to the onboard computer, and placement around cities (such as Tokyo) to transmit tourist information to visitor cell phones. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-21 2.9 SECURITY AND PRIVACY ISSUES With the adoption of RFID technology, a variety of security and privacy risks need to be addressed by both organizations and individuals: 2.9.1 TAG DATA RFID tags are considered “dumb” devices, in that they can only listen and respond, no matter who sends the request signal. This brings up risks of unauthorized access and modification of tag data. In other words, unprotected tags may be vulnerable to eavesdropping, traffic analysis, or denial of service attacks. We will look at each of these in turn: 2.9.1.1 Eavesdropping (or Skimming) Radio signals transmitted from the tag, and the reader, can be detected several meters away by other radio receivers. It is possible therefore for an unauthorized user to gain access to the data contained in RFID tags if legitimate transmissions are not properly protected. Any person who has their own RFID reader may interrogate tags lacking adequate access controls, and eavesdrop on tag contents. Researchers in the US has demonstrated a skimming attack on an RFID credit card, through which credit card information, such as the cardholder’s name and account information, could be skimmed if not properly encrypted. 2.9.1.2 Traffic Analysis Even if tag data is protected, it is possible to use traffic analysis tools to track predictable tag responses over time. Correlating and analysing the data could build a picture of movement, social interactions and financial transactions. Abuse of the traffic analysis would have a direct impact on privacy. 2.9.1.3 Denial of Service Attack The problems surrounding security and trust are greatly increased when large volumes of internal RFID data are shared among business partners. A denial of service attack on RFID infrastructure could happen if a large batch of tags has been corrupted. For example, an attacker can use the “kill” command, implemented in RFID tags, to make the tags permanently inoperative if they gain password access to the tags. In addition, an attacker could use an illegal high power radio frequency (RF) transmitter in an attempt to jam frequencies used by the RFID system, bringing the whole system to a halt. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-22 2.9.2 RFID READER INTEGRITY In some cases, RFID readers are installed in locations without adequate physical protection. Unauthorized intruders may set up hidden readers of a similar nature nearby to gain access to the information being transmitted by the readers, or even compromise the readers themselves, thus affecting their integrity. Unauthorized readers may also compromise privacy by accessing tags without adequate access controls. As a result, information collected by readers and passed to the RFID application may have already been tampered with, changed or stolen by unauthorized persons. An RFID reader can also be a target for viruses. In 2006, researchers demonstrated that an RFID virus was possible. A proof-of-concept self-replicating RFID virus was written to demonstrate that a virus could use RFID tags to compromise backend RFID middleware systems via an SQL injection attack. 2.9.3 PERSONAL PRIVACY As RFID is increasingly being used in the retailing and manufacturing sectors, the widespread item-level RFID tagging of products such as clothing and electronics raises public concerns regarding personal privacy. People are concerned about how their data is being used, whether they are subject to more direct marketing, or whether they can be physically tracked by RFID chips. If personal identities can be linked to a unique RFID tag, individuals could be profiled and tracked without their knowledge or consent. For instance, washing clothes tagged with RFID does not remove the chips, since they are specially designed to withstand years of wear and tear. It is possible that everything an individual buys and owns is identified, numbered and tracked, even when the individual leaves the store, as far as products are embedded with RFID tags. RFID readers can detect the presence of these RFID tags wherever they are close enough to receive a signal. 2.10 RFID SECURITY TRENDS Since RFID remains an emerging technology, the development of industry standards for protecting information stored on RFID chips is still being explored and strengthened. Research into the development and adaptation of efficient hardware for cryptographic functions, symmetric encryption, and message authentication codes and random number generators will improve RFID security. In addition, advances in RFID circuit design and manufacturing technology can also lower development costs releasing more resources in tags that can be used for other functions, such as allocating power consumption towards security features. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-23 Today, certain public key technologies are also being studied and in some cases deployed by RFID vendors. This helps improve confidentiality, user authentication and privacy of RFID tags and associated applications. RFID vendors are also conducting research into integrity and confidentiality issues around RFID reader infrastructure. Data can now be stored on a token using dynamic re-keying, where specific readers can rewrite a token’s credentials/signature, and verify the token’s identity. However, the cost and performance issues around using public key technologies in RFID applications have stalled its use for critical security applications. 2.10.1 APPROACHS FOR TACKLING SECURITY AND PRIVACY ISSUES There are a variety of solutions for tackling the security and privacy issues surrounding RFID. They can be categorized into the following areas: 1. Tag Data Protection. 2. Reader Integrity. 3. Personal Privacy. 2.10.1.1 SOLUTIONS FOR TAG DATA PROTECTION  Password Protection on Tag Memory Passwords can be used to protect tag data, preventing tags from being read without the original owner’s permission. But if the passwords for all the tags are identical, then the data becomes virtually public. However, if each tag is going to have a different or unique password, there may be millions of passwords that need to be recorded, meaning the reader would have to access the database and perform a lot of comparisons for each reading attempt.  Physical Locking of Tag Memory The tag manufacturer locks information such as a unique identifier into tag before the tag is released into an open environment. In other words, the chip is read-only and is embedded with information during the manufacturing process. This provides proof of origin. The limitation of this method is that no rewriting of data can be done on the tag chip. Additional memory would be required for storing modifiable or extra information and an algorithm would be needed for finding the latest tag data. This would result in higher memory cost and a larger size memory.  Authentication of the “Author” in Tag Memory The author or owner of the tag encrypts the tag data with his own private key (i.e. digitally signs the tag) and writes the encrypted data into tag memory along with the author’s name, a reference to his public key and the algorithm -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-24 used in non-encrypted form. When the reader wants to verify the authenticity of information, it retrieves the author’s name and other non-encrypted information from the tag to verify that the data has been actually written by the original author as claimed. However, if the RFID reader needs to update the tag with new data, a key management system is required in order to manage the private key. 2.10.1.2 SOLUTIONS FOR RFID READER INTEGRITY  Reader Protection Readers can reject tag replies with anomalies in response times or signal power levels which don’t match the physical properties of tags. If passive tags are used, this can be a way to prevent spoofing attempts.Readers can also use random frequencies with tags designed to follow a frequency dictated by the reader. Readers can change frequencies randomly so that unauthorised users cannot easily detect and eavesdrop on traffic On top of this, data transmitted between the reader and the RFID application server could require verification of the reader’s identity. Authentication mechanisms can be implemented between the reader and the backend application to ensure that information is passed to the valid processor.  Read Detectors RFID environments can be equipped with special devices to detect unauthorized read attempts or transmissions on tag frequencies. These read detectors may be used to detect unauthorized read/update attempts on tags, if they are used together with specially designed tags that can transmit signals over a reserved frequencies, indicating any attempts to kill or modify tags. 2.10.1.3 SOLUTIONS FOR PERSONAL PRIVACY  Kill Tag By executing a special “kill” command on a tagged product, the RFID tag will be “killed” and can never be re-activated. This “kill” command may disconnect the antenna or short-circuit a fuse. This ensures that the tag cannot be detected any further, and thus protects the privacy of the individual who possesses the product. However, there may be instances where tags should not be “killed”. A store may wish for example to re-detect the tags on defective products returned by customers. Also, smart-cards embedded with RFID chips for access control will need to be activated continuously.  Faraday Cage An RFID tag can be shielded with a container made of metal mesh or foil, known as a “Faraday Cage”. This foil-lined container can block radio signals of certain frequencies and thus protect tagged products from being detected. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • HISTORY OF RFID Chapter 2 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـ‬‫ــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |2-25 However, this approach might not work in some situations. For example, it is difficult to wrap foil-lined containers around tags used in clothing for pets and people.  Active Jamming Active jamming of RF signals refers to the use of a device that actively broadcasts radio signals in order to disrupt the operation of any nearby RFID readers. This physical means of shielding may disrupt nearby RFID systems. However, the use of such a device may be illegal, depending on the broadcasting power of the device and government regulations in force. There is a risk of severe disruption to all nearby RFID systems if the jamming power is too strong. 2.11 “RSA” Selective Blocker Tag A blocker tag is a passive RFID device that uses a sophisticated algorithm to simulate many ordinary RFID tags simultaneously. It provides an endless series of responses to RFID readers through the use of two antennas to reflect back two bits simultaneously, thereby preventing other tags from being read, performing a kind of passive jamming. However, this approach gives individuals a lot of control. In addition, a blocker tag may be used maliciously to circumvent RFID reader protocols by simulating multiple tag identifiers. Conclusion While the use of RFID technology is increasing across a range of different industries, the associated security and privacy issues need to be carefully addressed. Because RFID tags come in different flavors, there is no overall, generic RFID security solution. Some low-cost passive and basic tags cannot execute standard cryptographic operations like encryption, strong pseudorandom number generation, and hashing. Some tags cost more than basic RFID tags, and can perform symmetric-key cryptographic operations. Organizations wishing to use RFID technology need to therefore evaluate the cost and security implications as well as understand the limitations of different RFID technologies and solutions. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 1 3 RFID CHIP TAG 3.1 Definition An RFID tag is a device that can store and transmit data to a reader in a contactless manner using radio waves. There are two main components present in the RFID tag: 1. Firstly, a small silicon chip or integrated circuit which contains a unique identification number (ID). 2. Secondly, an antenna that can send and receive radio waves. These two components can be tiny: the antenna consists of a flat, metallic conductive coil rather than a protruding FM-style aerial and the chip is potentially less than half a millimeter. These two components are usually attached to flat plastic tags that can be fixed to a physical item. These tags can be quite small, thin and, increasingly, easily embedded within packaging, plastic cards, tickets, clothing labels, pallets and books. There are two main types of tags: passive and active. Passive tags are currently the most widely deployed as they are the cheapest to produce. 3.2 Tag Characteristics The market for RFID tags includes numerous different types of tags, which differ greatly in their cost, size, performance, and security mechanisms. Even when tags are designed to comply with a particular standard, they are often further customized to meet the requirements of specific applications. Understanding the major tag characteristics can help those responsible for RFID systems identify the tag characteristics required in their environments and applications. Major characteristics of tags include: i. Identifier format, ii. Power source, iii. Operating frequencies, iv. Functionality, and v. Form factor. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 2 3.2.1 Identifier Format Every tag has an identifier that is used to uniquely identify it. There are a number of data formats available for encoding identifiers on tags. System designers often want to use identifiers that have a standard structure, with certain groups of bits representing particular fields. A tag identifier format that is used across many industry sectors is the Electronic Product Code (EPC).This format was developed by the industry group EPC global. EPC global is a joint venture between Global Standards One (GS1), which was formerly known as European Article Numbering (EAN) International, and GS1 US, which was formerly known as the Uniform Code Council (UCC). The tag identifier format consists of four data fields: 1. The Header, which specifies the EPC type. 2. The EPC Manager ID, which uniquely identifies the organization that is responsible for assigning the object class and serial number, bits (often the manufacturer of the item). 3. The Object Class, which identifies a class of objects, such as a certain model of television set. 4. The Serial Number, which uniquely describes the instance of that class of objects (e.g., a particular television set). Using a standard identifier format makes it easier for organizations to decode identifiers. When a machine reads a standard identifier, it can parse the identifier and decode its fields. The machine may need to request information from a remote computer to look up an identifier. When the database is distributed across several organizations and many servers, a standard identifier format with specified fields greatly facilitates the look up process. Therefore, standard identifier formats should be used whenever an RFID system will be used across multiple organizations. If an organization does not expect its tag identifiers to be read by external parties or is concerned that the association of a tag with the organization or specific classes of objects is a business or privacy risk, then it may choose to develop and implement its own identifier format that does not reveal this information. Options include random or serialized identifiers that do not reveal information about the tagged item (e.g., its object class). Such identifiers can be encoded on many standards-based tags. These tags reserve memory for standard identifier formats but the memory does not have to be used for that purpose. The data format chosen for an RFID system should be adequate for the entire life cycle of the system. Certain data formats may not have enough bits to uniquely encode all the tags that will be used in a particular application. For example, a supply chain RFID system may need longer identifiers to identify the large number of items that it will manage. The -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 3 identifier data format also has security implications. For example, standard formats such as EPC allow an adversary to quickly obtain intelligence about a business activity by decoding the manager and object class fields. 3.2.2 Power Source Tags need power to perform functions such as sending radio signals to a reader, storing and retrieving data, and performing other computations (e.g., those needed for security mechanisms). Tags can obtain this power from a battery or from electromagnetic waves emitted by readers that induce an electric current in the tags. The power requirements of a tag depend on several factors, including the operating distance between the tag and the reader, the radio frequency being used, and the functionality of the tag. In general, the more complex the functions the tag supports, the greater its power requirements. For example, tags that support cryptography or authentication require more energy than tags that are limited to transmitting an identifier. Tags are categorized into four types based on the power source for communication and other functionality: i. Passive ii. Active iii. Semi-passive iv. Semi-active 3.2.2.1 A passive tag The electromagnetic energy it receives from a reader’s transmission to reply to the reader. The reply signal from a passive tag, which is also known as the backscattered signal,5 has only a fraction of the power of the reader’s signal. This limited power significantly restricts the operating range of the tag. It also means that passive tags can only support data processing of limited complexity. On the other hand, passive tags typically are cheaper, smaller, and lighter than other types of tags, which are compelling advantages for many RFID applications. Passive RFID is where the RFID tag’s power is derived from the Reader’s electromagnetic or inductive field. The RFID tag has no battery and is typically low-cost, robust and can last “forever”. The tag stores energy from the Reader’s electromagnetic/inductive field and passes information back to the Reader by modulating the Reader’s own radiated energy. Passive RFID tags are less costly to manufacture than active RFID tags and require almost zero maintenance. These traits of long-life and low-cost make passive RFID tags attractive to retailers and manufacturers for unit, case, and pallet-level tagging in open- loop supply chains. Open-loop supply chains typically allow little to no regulation of -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 4 whether RFID tags leave the control of the tag owner or originator. Because of their dependence on external reader energy fields and their low reflected power output, passive RFID tags have a much shorter read range (from a few inches for tags using load modulation up to a few meters for those using backscatter modulation) as well as lower read reliability when compared to active RFID tags. Figure 3.1: Passive Tag Backscatter Modulation. Note that neither of these two techniques allows passive RFID tags to communicate directly with 802.11 infrastructure access points. All communication from the passive RFID tag occurs via the RFID reader. The passive RFID tag is available commercially packaged in a wide variety of designs, from mounting on a simple substrate to creating a classic "hard" tag sandwiched between adhesive and paper (commonly referred to as an RFID "smart" label). The form factor used depends primarily on the application intended for the passive RFID tag and can represent the bulk of the passive RFID tag cost. A contactless smart card is a special type of passive RFID tag that is widely used today in various areas (for example, as ID badges in security and loyalty cards in retail). The data on this card is read when it is in close proximity to a reader. The card does not need to be physically in contact with the reader for reading. A passive tag consists of the following main components:  Microchip  Antenna An active tag relies on an internal battery for power. The battery is used to communicate to the reader, to power on-board circuitry, and to perform other functions. Active tags can communicate over greater distance than other types of tags, but they have a finite battery -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 5 life and are generally larger and more expensive. Since these tags have an internal power supply, they can respond to lower power signals than passive tags. Active RFID is where the RFID tag has its own power source (typically a small battery). The tag is actually a transceiver and responds to received commands from the Reader and “actively” transmits data back. Active tags can use any ISM or licensed frequency band, the most common being 850-950MHz and 2.4GHz. The range is dependent on both the tag and Reader transmitter power and receiver sensitivity. Active tags typically spend long periods “asleep” to prolong battery life. Range can be 10’s of meters to several kilometers. 3.2.2.2 An active tag Active tags can be relatively large and have a finite life (batteries need to be changed) and are significantly more expensive than passive tags. Active Tag Readers use a similar level of technology to the tags and can be relatively inexpensive. Some tags can use “passive” circuitry to "wake up" and then “actively” transmit data, this technique offers longer battery life Active RFID tags have an on-board power source (for example, a battery; other sources of power, such as solar, are also possible) and electronics for performing specialized tasks. An active tag uses its on-board power supply to transmit its data to a reader. It does not need the reader's emitted power for data transmission. The on-board electronics can contain microprocessors, sensors, and input/output ports powered by the on-board power source. Therefore, for example, these components can measure the surrounding temperature and generate the average temperature data. The components can then use this data to determine other parameters such as the expiry date of the attached item. The tag can then transmit this information to a reader (along with its unique identifier). You can think of an active tag as a wireless computer with additional properties (for example, like that of a sensor or a set of sensors). In tag-to-reader communication for this type of tag, a tag always communicates first, followed by the reader. Because the presence of a reader is not necessary for data transmission, an active tag can broadcast its data to its surroundings even in the absence of a reader. This type of active tag, which continuously transmits data with or without the presence of a reader, is also called a transmitter. Another type of active tag enters a sleep or a low-power state in the absence of interrogation by a reader. A reader wakes up such a tag from its sleep state by issuing an appropriate command. This state saves the battery power, and therefore, a tag of this type generally has a longer life compared to an active transmitter tag. In addition, because the tag transmits only when interrogated, the amount of induced RF noise in its environment -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 6 is reduced. This type of active tag is called a transmitter/receiver (or a transponder). As you can understand from this discussion, you cannot accurately call all tags transponders. The reading distance of an active tag can be 100 feet (30.5 meters approximately) or more when the active transmitter of such a tag is used. An active tag consists of the following main components:  Microchip. The microprocessor size and capabilities are generally greater than the microchips found in passive tags.  Antenna. This can be in the form of an RF module that can transmit the tag's signals and receive reader's signals in response. For a semi-active tag, this is composed of thin strip(s) of metal such as copper, similar to that of a passive tag.  On-board power supply.  On-board electronics. 3.2.2.3 A semi-passive tag A semi-passive tag is a passive tag that uses a battery to power on-board circuitry, but not to produce return signals. When the battery is used to power a sensor, they are often called sensor tags. They typically are smaller and cheaper than active tags, but have greater functionality than passive tags because more power is available for other purposes. Some literature uses the terms “semi-passive” and “semi-active” interchangeably. Semi-passive RFID tags overcome two key disadvantages of pure passive RFID tag design The lack of a continuous source of power for onboard telemetry and sensor asset monitoring circuits and Short range. Semi-passive tags differ from passive tags in that they use an onboard battery to provide power to communication and ancillary support circuits, such as temperature and shock monitoring. It is interesting to note that although they employ an onboard power source, semi-passive RFID tags do not use it to directly generate RF electromagnetic energy. Rather, these tags typically make use of backscatter modulation and reflect electromagnetic energy from the RFID reader to generate a tag response similar to that of standard passive tags (see Figure 3.2). The onboard battery is used only to provide power for telemetry and backscatter enabling circuits on the tag, not to generate RF energy directly. Semi-passive RFID tags operating in the ISM band can have a range of up to 30 meters with onboard lithium cell batteries lasting several years. Range is vastly improved over conventional passive RFID tags primarily because of the use of a backscatter-optimized antenna in the semi-passive design. Unlike a conventional backscatter-modulated passive RFID tag, the antenna contained in a semi-passive tag is dedicated to backscatter modulation and there is no -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 7 dependence on the semi-passive RFID tag antenna to be a reliable conduit of power for the tag. Therefore, the semi-passive tag antenna can be optimized to make most efficient use of the backscatter technique and provide far better performance than purely passive RFID tag antenna designs. Figure 3.2: Backscatter Modulation in Semi-Passive RFID Tags. 3.2.2.4 A semi-active tag A semi-active tag is an active tag that remains dormant until it receives a signal from the reader to wake up. The tag can then use its battery to communicate with the reader. Like active tags, semi-active tags can communicate over a longer distance than passive tags. Their main advantage relative to active tags is that they have a longer battery life. The waking process, however, sometimes causes an unacceptable time delay when tags pass readers very quickly or when many tags need to be read within a very short period of time. Semi-active tags have an on-board power source (for example, a battery) and Figure 3.3:Options for Tag Power/TransmitConfiguration. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 8 electronics for performing specialized tasks. The on-board power supply provides energy to the tag for its operation. However, for transmitting its data, a semi-active tag uses the reader's emitted power. A semi-active tag is also called a battery-assisted tag. In tag-to- reader communication for this type of tag, a reader always communicates first, followed by the tag. A passive tag A passive tag is shown in a bit more detail in Figure 3.4. An antenna structure interacts with impinging electromagnetic fields, producing a high-frequency (RF) voltage. The voltage is rectified by a diode (a device which only allows current to flow in one direction), and the resulting signal is smoothed using a storage capacitor to create a more- or-less constant voltage that is then used to power the tag’s logic circuitry and memory access. Passive tag memory circuitry is always nonvolatile since the tag power is usually off. A similar rectification circuit, using a smaller capacitance value to allow the voltage to vary on the timescale of the reader data, is used to demodulate the information from the reader. This technique is known as envelope detection. Finally, to transmit information back to the reader, the tag changes the electrical characteristics of the antenna structure so as to modify the signal reflected from it, -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 9 somewhat analogous to tilting a mirror. Here we have shown a field-effect transistor (FET) used as a switch; when the FET is turned on, the antenna is grounded, allowing a large current to flow, and when it is off, the antenna floats allowing very little antenna current. Real tags are a bit more sophisticated but use an essentially similar mechanism for modulation. The same conceptual scheme is used for all frequency bands, though the details of implementation differ for LF, HF, and UHF tags. The tremendous advantage of a passive tag is its simplicity and consequent low cost. Passive tags have no battery, no crystal frequency reference, and no synthesizer to create a high-frequency signal, no power amplifier to amplify the synthesizer signal, and no low-noise amplifier to capture the reader signal. These functions are relatively expensive compared to logic circuitry and in some cases (e.g. a crystal), would require placement of a separate component onto the tag. Their elimination greatly reduces the cost of tag manufacture. Furthermore, because there is no battery, passive tags need no maintenance and last as long as the materials of which they are composed endure. In exchange for this low cost, passive tags give up a lot. Read range is limited by the need to power up the circuitry and so is short relative to the range at which signals from the reader could be detected by the tag; the limitation is particularly acute at UHF, where propagation limited read range might be large. The tags are also generally dumb. Because they depend on received RF for power, they must be designed to use very little of it. Computational power is minimized to avoid power consumption, so the readers must use very simple protocols to avoid overtaxing the tags, and integration of sensors is limited by the lack of power except when near a reader. Security and privacy are necessarily compromised due to the limited resources available to implement cryptographic algorithms, though this deficiency can be ameliorated for HF tags if short range is acceptable. Passive tags, particularly at UHF frequencies, are unreliable relative to more sophisticated systems: they won’t power up at all unless they receive a strong reader signal and are thus often not seen. Furthermore, the limited computational capability means that many of the techniques used to improve link quality for more capable radios, such as error-correcting codes, interleaving, gain adjustment, and retransmission, are not practical for passive tags. An example of a typical UHF passive tag is shown in Figure3.5. The tag is almost wholly composed of the plastic substrate or inlay and the antenna structure. The single very small IC is mounted on a strap (which conceals it from direct view in this image). The whole assembly is much less than 1 mm thick and can thus be used in applications where physically larger tags might be esthetically objectionable or subject to mechanical damage. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 10 Figure 3.4: Schematic Depiction of Simple Passive RFID Tag. Figure 3.5: Typical Commercial Passive UHF Tag. A Semi-passive tag Figure 3.6: Schematic Depiction of Simple Semi-passive Tag. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 11 Semi-passive tags can achieve ranges in the tens of meters to as much as 100 m and are much more reliable than passive tags in the sense that they are much more likely to respond to a valid interrogation. They are often used in automobile tolling applications (where a missed tag translates into missed revenue or an inappropriate citation) and in tracking of airplane parts and other high-value reusable assets. The tradeoff is that they require a battery with concomitant increases in size, cost, and maintenance requirements. Battery life is improved by operating at very low duty cycle, and/or using a detector circuit to keep most of the system off except when a reader signal is probably present. 3.2.3 Operating Frequencies Classes of RFID frequency types include the following: Low frequency (LF) High frequency (HF) Ultra high frequency (UHF) Microwave frequency The following subsections discuss these frequency types. 3.2.3.1 Low Frequency (LF) Frequencies between 30 KHz and 300 KHz are considered low, and RFID systems commonly use the 125 KHz to 134 KHz frequency range. A typical LF RFID system operates at 125 KHz or 134.2 KHz. RFID systems operating at LF generally use passive tags have low data-transfer rates from the tag to the reader, and are especially good if the operating environment contains metals, liquids, dirt, snow, or mud (a very important characteristic of LF systems). Active LF tags are also available from vendors. Because of the maturity of this type of tag, LF tag systems probably have the largest installed base. The LF range is accepted worldwide. 3.2.3.2 High Frequency (HF) HF ranges from 3 MHz to 30 MHz, with 13.56 MHz being the typical frequency used for HF RFID systems. A typical HF RFID system uses passive tags, has a slow data-transfer rate from the tag to the reader, and offers fair performance in the presence of metals and liquids. HF systems are also widely used, especially in hospitals (where it does not interfere with the existing equipment). The HF frequency range is accepted worldwide. The next frequency range is called very high frequency (VHF) and lies between 30 and 300 MHz unfortunately; none of the current RFID systems operate in this range. Therefore, this frequency type is not discussed any further. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 12 3.2.3.3 Ultra High Frequency (UHF) UHF ranges from 300 MHz to 1 GHz. A typical passive UHF RFID system operates at 915 MHz in the United States and at 868 MHz in Europe. A typical active UHF RFID system operates at 315 MHz and 433 MHz A UHF system can therefore use both active and passive tags and has a fast data-transfer rate between the tag and the reader, but performs poorly in the presence of metals and liquids (not true, however, in the cases of low UHF frequencies such as 315 MHz and 433 MHz). UHF RFID systems have started being deployed widely because of the recent RFID mandates of several large private and public enterprises, such as several international and national retailers, the U.S. Department of Defense, and so on. The UHF range is not accepted worldwide. 3.2.3.4 Microwave Frequency Microwave frequency ranges upward from 1 GHz. A typical microwave RFID system operates either at 2.45 GHz or 5.8 GHz, although the former is more common, can use both semi-active and passive tags, has the fastest data-transfer rate between the tag and the reader, and performs very poorly in the presence of metals and liquids. Because antenna length is inversely proportional to the frequency the antenna of a passive tag operating in the microwave range has the smallest length (which results in a small tag size because the tag microchip can also be made very small). The 2.4 GHz frequency range is called Industry, Scientific, and Medical (ISM) band and is accepted worldwide. Radio waves are susceptible to interference from various sources, such as the following:  Weather conditions such as rain, snow, and other types of precipitation. However, as mentioned before, these are not an issue at LF and HF.  The presence of other radio sources such as cell phones, mobile radios, and so on.  Electrostatic discharge (ESD). ESD is a sudden flow of electrical current through a material that is an insulator under normal circumstances. If a large potential difference exists between the two points on the material, the atoms between these two points can become charged and conduct electric current. Material LF 30-300 kilohertz (kHz) HF 3-30 MHz UHF 300 MHz-1 GHz Microwave > 1 GHz Clothing Transparent Transparent Transparent Transparent Dry Wood Transparent Transparent Transparent Absorbent Graphite Transparent Transparent Opaque Opaque Metals Transparent Transparent Opaque Opaque -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 13 Motor Oil Transparent Transparent Transparent Transparent Paper Products Transparent Transparent Transparent Transparent Plastics Transparent Transparent Transparent Transparent Water Transparent Transparent Absorbent Absorbent Wet Wood Transparent Transparent Absorbent Absorbent Table 3.1: Impact of Selected Materials on RF Transmissions9. Frequency Range RFID Applications Possible Interference Sources in US Less than 500 kHz Access control, animal tagging, automobile immobilizers, EAS systems, inventory control, and track and traceability applications Maritime radio and radio navigation applications 1.95 MHz - 8.2 MHz EAS systems Aeronautical radio, amateur, land mobile, maritime mobile radios, and radio location applications 13.553 - 13.567 MHz Access control, item-level tagging, EAS systems, and smart card applications ISM applications and private land mobile radio 433.5 - 434.5 MHz In-transit visibility and supply chain applications Amateur radio and radio location applications 902 - 928 MHz Railcar, supply chain, and toll road applications ISM applications including cordless phones and radio location 2.40 - 2.50 GHz Real-time location systems (RTLS), and supply chain applications ISM applications including Bluetooth, cordless phones, and Wi-Fi as well as radio location, and satellite technologies Table 3.2: Common Sources of RF Interference. 3.2.4 Functionality 3.2.4.1 Memory Memory that is nonvolatile enables data to be stored on tags and retrieved at a later time. This memory is either write once, read many (WORM) memory or re-writeable memory, which can be modified after initialization. Non-volatile memory enables more flexibility in the design of RFID systems because RFID data transactions can occur without concurrent access to data stored in an enterprise subsystem. However, adding memory to a tag increases its cost and power requirements. Section 3 discusses RFID application requirements and provides additional information about the -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 14 circumstances under which the use of re-writable memory would be a desirable approach. In general, when this document refers to memory, it is referring to non-volatile memory. In contrast, volatile memory, which is also used in tags, supports tag computations and does not retain data after it is powered down. 3.2.4.2 Read Only (RO) An RO tag can be programmed (that is, written) just once in its lifetime. The data can be burned into the tag at the factory during the manufacturing stage. To accomplish this, the individual fuses on the tag microchip are burned permanently using a fine-pointed laser beam. After this is done, the data cannot be rewritten for the entire lifetime of the tag. Such a tag is also called factory programmed. The tag manufacturer supplies the data on the tag, and the tag users typically do not have any control over it. This type of tag is good for small applications only, but is impractical for large manufacturing or when tag data needs to be customized based on the application. This tag type is used today in small pilots and business applications. 3.2.4.3 Write Once, Read Many (WORM) A WORM tag can be programmed or written once, which is generally done not by the manufacturer but by the tag user right at the time when the tag needs to be created. In practice, however, because of buggy implementation, it is possible to overwrite particular types of WORM tag data several times (about 100 times is not uncommon)! If the data for such a tag is rewritten more than a certain number of times, the tag can be damaged permanently. A WORM tag is also called field programmable. This type of tag offers a good price-to- performance ratio with reasonable data security, and is the most prevalent type of tag used in business today. 3.2.4.4 Read Write (RW) An RW tag can be reprogrammed or rewritten a large number of times. Typically, this number varies between 10,000 and 100,000 times and above! This rewritability offers a tremendous advantage because the data can be written either by the readers or by the tag itself (in case of active tags). An RW tag typically contains a Flash or a FRAM memory device to store its data. An RW tag is also called field programmable or reprogrammable. Data security is a challenge for RW tags. In addition, this type of tag is most expensive to produce. RW tags are not widely used in today's applications, a fact that might change in the future as the tag technology and applicability increases with a decrease in tag cost. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 15 3.2.4.5 Environmental sensors The integration of environmental sensors with tags is an example of the benefit of local memory. The sensors can record temperature, humidity, vibration, or other phenomena to the tag’s memory, which can later be retrieved by a reader. The integration of sensors significantly increases the cost and complexity of the tags. Moreover, while many tag operations can be powered using the electromagnetic energy from a reader, this approach is not workable for sensors, which must rely on battery power. Tags integrated with sensors typically are only used with high-value, environmentally sensitive, or perishable objects worthy of the additional expense. 3.2.4.6 Security functionality, such as password protection & cryptography Tags with on-board memory are often coupled with security mechanisms to protect the data stored in that memory. For example, some tags support a lock command that, depending on its implementation, can prevent further modification of data in the tag’s memory or can prevent access to data in the tag’s memory. In some cases, the lock command is permanent and in other cases, a reader can “unlock” the memory. EPC global standards, standards developed jointly by the International Organization for Standardization (ISO) and the International Electro technical Commission (IEC), and many proprietary tag designs support this feature. Some RFID systems support advanced cryptographic algorithms that enable authentication mechanisms and data confidentiality features, although these functions are most commonly found on RFID-based contactless smart cards and not tags used for item management. Some tags offer tamper protection as a physical security feature. 3.2.4.7 Privacy protection mechanisms EPC global tags support a feature called the kill command that permanently disables the tag from responding to subsequent commands. The primary objective of the kill command is to protect personal privacy. Unlike the lock command, the kill command is irreversible. The kill command also prevents wireless access to a tag’s identifier, in addition to any memory that may be on the tag. While the lock command provides security, the primary objective of the kill command is personal privacy. RFID tags could potentially be used to track individuals that carry tagged items or wear tagged articles of clothing when the tags are no longer required for their intended use, such as to expedite checkout or inventory. The ability to disable a tag with the kill command provides a mechanism to prevent unauthorized access to and illegitimate use of product information stored in the tag. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 16 3.2.5 Form Factor The form factor of a tag refers to its shape, size, packaging, and handling features. To a large extent, a tag’s form factor is determined by the characteristics previously discussed, such as power source and functionality. Some important aspects regarding a tag’s form factor include the size of the tag, the weight of the tag, and the method by which the tag is affixed to and removed from its associated object. Tags typically vary in size from smaller than a postage stamp to about the size of a common document stapler. Active tags typically are significantly larger and heavier than passive tags because they have an onboard power supply. Tags that integrate environmental sensors are also larger and heavier than those without this functionality. While increasing the computing functionality of a tag increases its cost and power requirements, it may not have an impact on its form factor because the microchip on a passive tag is one of the tag’s smallest components. On most passive tags, the largest component on the tag is its antenna. 3.3 Antennas A tag's antenna is used for drawing energy from the reader's signal to energize the tag and for sending and receiving data from the reader. This antenna is physically attached to the microchip. The antenna geometry is central to the tag's operations. Infinite variations of antenna designs are possible, especially for UHF, and designing an effective antenna for a tag is as much as an art as a science. The antenna length is directly proportional to the tag's operating wavelength. A dipole antenna consists of a straight electric conductor (for example, copper) that is interrupted at the center. The total length of a dipole antenna is half the wavelength of the used frequency to optimize the energy transfer from the reader antenna signal to the tag. A dual dipole antenna consists of two dipoles, which can greatly reduce the tag's alignment sensitivity. As a result, a reader can read this tag at different tag orientations. A folded dipole consists of two or more straight electric conductors connected in parallel and each half the wavelength (of the used frequency) long. When two conductors are involved, the resulting folded dipole is called 2-wire folded dipole. A 3-wire folded dipole consists of three conductors connected in parallel. A tag's antenna length is generally much larger than the tag's microchip, and therefore ultimately determines a tag's physical dimensions. An antenna can be designed based on several factors, such as the following: -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 17  Reading distance of the tag from the reader  Known orientation of the tag to the reader  Arbitrary orientation of the tag to the reader  Particular product type(s)  Speed of the tagged object  Specific operating condition(s)  Reader antenna polarization The connection points between a tag's microchip and the antenna are the weakest links of the tag. If any of these connection points are damaged, the tag might become nonfunctional or might have its performance significantly degraded. An antenna designed for a specific task (such as tagging a case) might perform poorly for a different task (such as tagging an individual item in the case). Changing antenna geometry randomly (just "hacking around;" for example, cutting or folding it) is not a good idea because this can detune the tag, resulting in suboptimal performance. However, someone who knows what he is doing can deliberately modify a tag's antenna to detune it (drilling a hole into it, for example) and actually increase the readability of the tag! Currently, a tag antenna is constructed with a thin strip of a metal (for example, copper, silver, or aluminum). In the future, however, it will be possible to print antennas directly on the tag label, case, and product packaging using a conductive ink that contains copper, carbon, or nickel. Effort is also currently underway to determine whether the microchip might be printed with such an ink, too. These future enhancements may enable you to print an RFID tag just as you do a bar code on the case and item packaging. As a result, the cost of an RFID tag might drop substantially below the anticipated $.05 per tag. Even without the ability to print a microchip, a printed antenna can be attached to a microchip to create a complete RFID tag much faster than attaching a metal antenna. 3.4 Basic Concepts 3.4.1 Tag Collision Contrary to popular belief, a reader can only communicate with one tag at a time. When more than one tag attempts to communicate with the reader at the same time, a tag collision is said to occur. In this case, in response to the reader's query, multiple tags reflect back their signals at the same time to the reader, confusing it. A reader then needs to communicate with the conflicting tags using what is called a simulation protocol. The algorithm that is used to mediate tag collisions is called an anti-collision algorithm. Currently, the following two types of anti-collision algorithms are most widely used: -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 18  ALOHA for HF  Tree Walking for UHF Using one of these anti-collision algorithms, a reader can identify several tags in its read zone in a very short period of time. Thus, it appears that this reader is communicating with these tags almost simultaneously. 3.4.2 Tag Readability Read robustness (also called read redundancy) is the number of times a particular tag can be read successfully when inside a read zone. As noted in the previous section, an RFID system has to be designed such that it has good read robustness for the tags. The speed of a tagged object can negatively impact the read robustness as the amount of time spent by the tag in the read zone decreases with an increase in its speed. This results in a decrease of read robustness for this tag. The number of tags present at one time in the read zone also can hamper read robustness because the number of tags that can be read by a reader per unit time is limited. 3.4.3 Information, Modulation, and Multiplexing Signals of interest for RFID are generally digitally modulated. A digitally modulated signal is a stream of distinct symbols. A simple example with substantial relevance for RFID is on–off keying (OOK). The signal power is kept large (m = 1) to indicate a binary ‘1’ and small or zero (m = 0) to represent a binary ‘0’. An example is shown in Figure 3.8. In OOK, each symbol is a period of fixed duration in which the signal power is either high or low. Each OOK symbol represents one binary bit, though other types of symbols can convey more than one bit each. Any circuit that can change the output power, such as a simple switch, can be used to create an OOK signal, and any circuit that can detect power levels can demodulate (extract the data from) the signal. For example, a diode—an electrical component that passes electrical current only in one direction and blocks current flow in the opposite direction—can rectify a high-frequency signal, turning it into pulses of DC. These pulses can be smoothed with a storage capacitor to produce an output signal that looks very much like the baseband signal m (t). If the diode responds rapidly, it can be used at very high frequencies. Modern diodes can operate up to over 1 GHz, allowing passive RFID tags to demodulate a reader signal using only a diode and capacitor. Unmodified OOK is admirably simple and seems promising as a method of modulating a reader signal. However, there is a problem with OOK for passive RFID a passive RFID tag depends on power obtained from the reader to run its circuitry. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 19 Figure 3.7: On–Off-Keyed Signal. If that power is interrupted, the tag cannot operate. However, imagine the case of an OOK signal containing a long string of binary 0s: in this case, m = 0 for as long as the data remains 0. The tag will receive no power during this time. If the data remains ‘0’ for too long, the tag will power off and need to be restarted, a situation not likely to be conducive to reliable operation. Even when some binary 1s are present, the power level delivered to the tag is strongly data dependent, an undesirable trait. A common solution to the power problem is to code the binary data prior to modulation. One RFID coding approach is known as pulse-interval encoding (PIE). A binary ‘1’ is coded as a short power-off pulse following a long full-power interval, and a binary ‘0’ is coded as a shorter full-power interval with the same power-off pulse (Figure 3.9). The resulting coded baseband signal m(t) is then used to modulate the carrier (Figure 3.10). PIE using equal low and high pulses for a ‘0’ ensures that at least 50% of the maximum power is delivered to the tag even when the data being transmitted contains long strings of zeros, and if the high is three times as long for a ‘1’, a random stream of equally mixed binary data will provide about 63% of peak power. Note that in this case, the data rate becomes dependent on the data: a stream of binary 0s will be transmitted more rapidly than a stream of binary 1s. A single symbol has two features—the off-time and on-time—but still conveys only one binary bit. (This scheme is used in EPC global Class 1 Generation 2 readers. Other passive RFID standards use slightly different coding schemes, all generally characterized by the desire to have the reader power on as much as possible to power the tag). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 20 Figure 3.8: Pulse-interval Coding Baseband Symbols (the function m (t)). Figure 3.9: Pulse-interval Coding with OOK Modulation of a Carrier Wave. 3.4.4 Backscatter Radio Links Passive and semi-passive RFID tags do not use a radio transmitter; instead, they use modulation of the reflected power from the tag antenna. Reflection of radio waves from an object has been a subject of active study since the development of radar began in the -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 21 1930s, and the use of backscattered radio for communications since Harry Stockman’s work. A very simple way to understand backscatter modulation is shown schematically in Figure 3.10 current flowing on a transmitting antenna leads to a voltage induced on a receiving antenna. If the antenna is connected to a load, which presents little impediment to current flow, it seems reasonable that a current will be induced on the receiving antenna. In the figure, the smallest possible load, a short circuit, is illustrated. This induced current is no different from the current on the transmitting antenna that started things out in the first place: it leads to radiation. A principle of electromagnetic theory almost always valid in the ordinary world, the principle of reciprocity, says that any structure that receives a wave can also transmit a wave. Figure 3.10: Modulated Backscatter Using a Transistor as a Switch. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 22 We shall make use of this principle in discussing antennas in greater detail shortly.) The radiated wave can make its way back to the transmitting antenna, induce a voltage, and therefore, produce a signal that can be detected: a backscattered signal. On the other hand, if instead a load that permits little current to flow that is, a load with large impedances placed between the antenna and ground, it seems reasonable that little or no induced current will result. In Figure 3.10, we show the largest possible load, an open circuit (no connection at all). Since it is currents on the antenna that lead to radiation, there will be no backscattered signal in this case. Therefore, the signal on the transmitting antenna is sensitive to the load connected to the receiving antenna. To construct a practical communications link using this scheme, we can attach a transistor as the antenna load (Figure 3.10). When the transistor gate contact is held at the appropriate potential to turn the transistor on, current travels readily through the channel, similar to a short circuit. When the gate is turned off, the channel becomes substantially nonconductive. Since the current induced on the antenna, and thus, the backscattered wave received at the reader, depend on the load presented to the antenna, this scheme creates a modulated backscattered wave at the reader. Note that the modulating signal presented to the transistor is a baseband signal at a low frequency of a few hundred kHz at most, even though the reflected signal to the reader may be at 915 MHz The use of the backscatter link means that the modulation switching circuitry in the tag only needs to operate at modest frequencies comparable to the data, not the carrier frequency, resulting in savings of cost and power. (Real RFID tag ICs are not quite this simple and may use a small change in capacitance to modulate the antenna. Note that in order to implement a backscattered scheme, the reader must transmit a signal. In many radio systems, the transmitter turns off when the receiver is trying to acquire a signal; this scheme is known as half-duplex to distinguish it from the case where the transmitter and receiver may operate simultaneously (known as a full-duplex radio). In a passive RFID system, the transmitter does not turn itself off but instead, transmits CW during the time the receiver is listening for the tag signal. RFID radios use specialized components known as circulators or couplers to allow only reflected signals to get to the receiver, which might otherwise be saturated by the huge transmitted signal. However, in a single-antenna system, the transmitted signal from the reader bounces off its own antenna back into the receiver, and the transmitted wave from the antenna bounces off any nearby objects such as desks, tables, people, coffee cups, metal boxes, and all the other junk that real environments are filled with, in addition to the poor little tag antenna we’re trying to see (Figure 3.11). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 23 If two antennas are used (one for transmit and one for receive), there is still typically some signal power that leaks directly from one to the other, as well as the aforesaid spurious reflections from objects in the neighborhood. The total signal at the receiver is the vector sum of all these contributions, most of which are much larger than the wanted tag signal, with appropriate amplitudes and phases, most of which are unpredictable a priori. Thus, the actual effect of a given change in the load on the tag antenna on the receiver signal is completely unpredictable and uncontrollable. For example, modulating the size of the tag antenna current (amplitude modulation) may not result in the same kind of change in the reader signal. In Figure 3.12, we show a case where changing the tag reflection from a large amplitude (HI) to a small amplitude (LO) causes the received signal to increase in magnitude without changing phase (the “AM” case). Changing the phase of the tag signal without changing the size of the reflected signal in order to symbolize a LO. Figure 3.11: Realistic Environments Create Many Reflected Waves in Addition to that from the wanted Tag. Figure 3.12: The Received Signal is not Simply Correlated to the Tag Signal; The AM Case. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 24 Assumes the Tag reduces its Scattered Magnitude without changing phase; the PSK Case. Assumes phase inversion without amplitude change. State may change the amplitude of the reader signal at constant phase (Figure 3.12, “PSK” case). The only thing we can say with any confidence is that when we make a change in the state of the tag antenna, something about the phase or amplitude of the reader signal will change. In order to make a backscatter link work, we need to choose a way to code the data that can be interpreted based only on these changes and not on their direction or on whether they are changes in phase or amplitude. As a consequence, all approaches to coding the tag signal are based on counting the number of changes in tag state in a given time interval, or equivalently on changing the frequency of the tag’s state changes. Therefore, all tag codes are variations of frequency- shift keying (FSK). It is important to note that the frequency being referred to here is not the radio carrier frequency of (say) 900 MHz but the tag (baseband) frequency of perhaps 100 or 200 kHz. A binary ‘1’ might be coded by having the tag flip its state 100 times per millisecond, and a binary ‘0’ might have 50 flips per millisecond. Because the frequency being changed is the frequency at which a carrier is being amplitude modulated, techniques like this are sometimes known as subcarrier modulation. Let’s look at one specific example of tag coding, usually known as FM0 (Figure 3.13). InFM0, the tag state changes at the beginning and end of every symbol. In addition, a binary 0 has an additional state change in the middle of the symbol. Note that, unlike OOK, the actual tag state does not reliably correspond to the binary bit: for example, in the left-hand side of the figure, two of the binary ‘1’ symbols have the tag in the LO state and another ‘1’ symbol has the tag in the HI state. Remember, the reader can’t reliably distinguish which state is which but can only count transitions between them. The right side of the figure shows the baseband signal corresponding to a series of identical binary bits to clarify the correspondence of binary ‘0’s with a frequency twice as high as that of binary ‘1’s. Figure 3.13: FM0 Encoding of Tag Data. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 25 Different tag coding schemes can be used to adjust the offset from the carrier frequency at which the signal from the tags is found. As we will find in Chapter 5, readers have an easier time seeing a tag signal when it is well separated from their own carrier frequency, so higher subcarrier frequencies help improve the ability to read a tag signal. However, if the separation is large compared to the channel size, the tag signal might lie on the signal of another reader in a different channel. Just as with readers, increasing the data rate of a tag signal tends to spread the spectrum out in frequency. To have a flexible choice of tag data rates while minimizing noise, the reader needs to be able to adapt the band of frequencies it tries to receive, adding cost and complexity. In real receivers, noise and interference may be present as well as the desired signal. A certain minimum signal-to-noise ratio (S/N) is necessary for each type of modulation in order that it can be reliably decoded by the receiver. The exact (S/N) threshold depends on how accurate you’re trying to be and to a lesser extent on the algorithms used for demodulation/decoding. For RFID using FM0, (S/N) of around 10 or better (10 dB or more) is usually sufficient. (Requirements for demodulation of reader symbols, like PIE, in the tag are generally similar.) As we will see in Chapter 8, modern protocols provide alternative modulations that can operate with smaller (S/N) ratios, at the cost of a reduction in the tag data rate. 3.4.5 Link Budgets Let’s summarize the message of the last couple of sections. To transmit to a tag, a reader uses amplitude modulation to send a series of digital symbols. The symbols are coded to ensure that sufficient power is always being transmitted regardless of the data contained within in. The received signal can be demodulated using a very simple power detection scheme to produce a baseband voltage, which is then decoded by the tag logic. The whole scheme is depicted in Figure 3.14. Figure 3.14: Schematic Depiction of Reader-to-tag Data Link. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 26 Figure 3.15: Schematic Depiction of Tag-to-reader Data Link. Figure 3.15 shows the corresponding tag-to-reader arrangements. The tag codes the data it wishes to send and then induces changes in the impedance state of the antenna. The reader CW signal bounces off the tag antenna (competing with other reflections) and is demodulated by the reader receiver and then decoded back into the transmitted data. While we have alluded several times to the fact that the reader must power the tag, so far we have avoided coming to grips with the crucial associated question of just how much power the tag needs to get and just how far we can go from the reader and still get it. The amount of power that one needs to deliver to a receiver across a wireless link in order that the transmitted data is successfully received is known as the link budget. Since readers and tags both talk, for an RFID system there are two separate link budgets, one associated with the reader-to-tag communication (the forward link budget) and one with the tag reply to the reader (the reverse link budget).In order to find the forward link budget, we need to know the following: • How much power can the reader transmit? • How much power does the tag receive as a function of distance from the reader? • How much power does the tag need to turn on? • How much power does the tag need to decode the reader signal? Let’s examine each question in turn. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 27 3.4.6 Reader Transmit Power The reader transmit power is set by a combination of practicality and regulation. Most RFID equipment operates in spectrum set aside for unlicensed use by the governmental body that regulates radio operation in a given jurisdiction. For example, in the United States, the FCC allows operation in the band 902–928 MHz without requiring that the person operating the equipment have a license to do so. However, the equipment itself must obey certain operating limitations in order to allow unlicensed use. Relevant for us at the moment is the maximum transmit power, which cannot exceed 1 W. While not all readers will deliver a watt, and in some applications, we may intentionally reduce transmitted power, in many cases a UHF reader will be operated at the legal limit. So let’s assume we transmit 1 W of total power. 3.4.7 Path Loss The difference between the power delivered to the transmitting antenna and that obtained from the receiving antenna is known as the path loss. In general, finding the path loss requires knowing something about the details of the antenna operation, and we shall discuss the relevant measurements and terminology shortly. However, to get started, we will use the simplest possible (not very accurate) approach: let us assume that the transmitting antenna radiates in all directions with the same power density that is the transmitter is isotropic. We can picture the radiated power as being uniformly distributed over a spherical surface at any given distance r from the reader antenna (Figure 3.16). Some of this power can be collected by a tag antenna. It is reasonable to guess that the amount of power collected should be proportional to the density of power impinging on the tag and dimensionally necessary that the constant of proportionality be an area, often known as the effective aperture Ae of the tag antenna. Since in the isotropic case the power density at a distance r is the ratio of the transmitted power PTX to the sphere area, we can find the power received by the tag PRX: 𝑃𝑅𝑋 = 𝑃𝑇𝑋 𝐴𝑒 4𝜋𝑟2 In order to get numbers out, we need a value for the effective aperture. It is not trivial to derive what this area should be, but it is plausible (and correct) to guess that the effective aperture of an antenna around a half-wavelength long might correspond to a square around a half wavelength on a side. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 28 The actual answer for an isotropic antenna (which a tag isn’t quite) is 𝐴𝑒 = 𝜆2 4𝜋 ≈ 86 𝑐𝑚2 @ 915 𝑀𝐻𝑧 Figure 3.16: An Isotropic Antenna Radiates Power Uniformly Over the Surface of a Sphere. With a value for the aperture, we can now obtain an estimate of the path loss for our proposed isotropic link. At a distance of 1 m, the spherical surface has an area of 12.6 m2, so for 1 watt of transmit power, we get about 1(86) / (126,000) = 7 x 10- 4 = 0.7 mW (-1.6 dBm). Since we started with a watt or 30 dBm, the path loss is about 32 dB. Since the area scales with the square of the radius, we can very easily scale path loss, especially in dB: a factor of 10 in distance adds 20 dB to the path loss (20 dB/decade). A factor of 3 is worth just a bit less than half of this (about 9.5 dB). So at 3 m, the path loss is about (32+9.5) ≈ 41 dB, and at 10 m it is about 52 dB. 3.4.8 Tag Power Requirement The tag antenna needs to deliver enough power to turn the tag IC on. Modern tag ICs actually consume around 10–30 μW to operate when being read (much more power is required to write new data to the tag memory). This power must be supplied by a rectifying circuit, which is about 30% efficient, due primarily to the substantial turn-on -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 29 voltage required to make current flow through the diodes. As a consequence, tags require about 30–100 μW of power to be delivered from the antenna to provide the required 10– 30 μ W of power to the chip. For simplicity, let us for the moment use a rather conservative 100 μW (-10 dBm) as the required threshold power. If we started at the transmitter with 1 watt (30 dBm), and we need to end up with −10 dBm, we have room for a path loss of (30 - (-10)) = 40 dB. 3.4.9 Factors which affect read range for RFID Read range for an RFID tag is affected by many factors, including: 1. Passive, BAP, NFC or Active RFID? 2. RFID frequency : LF, HF or UHF 3. Surrounding materials 4. Type of tag 5. Type of reader 6. Orientation 7. Time to read 8. Number of tags being read 9. Density of tags Given all of the above, the only general comment that we can make is that read range can be anywhere from half an inch to a hundred meters. For more information, please read on... We address each of these issues in the following sections. Note that we have given general information assuming a typical working environment. The numbers we quote below are conservative, and reflect the different factors that affect read range. In all cases the numbers could be improved considerably if each of the factors above was optimized. So please take the numbers in the way they are intended, as a general guideline. 3.4.9.1 Passive, BAP, NFC or Active RFID? Passive RFID is the most common. Power to the tags is provided by the reader, and the tag has no power source. Advantages include low cost, indefinite life, small size. BAP tags (Battery Assisted Passive Tags) have an internal battery. They are more tolerant of surrounding materials, but they are more expensive, slightly larger, and have a finite life, typically two years. NFC, for near field communication is essentially using passive RFID Tag technology to communicate in both directions. Low range is essentially a benefit in this case, as there is less chance for confusion as to which tag is communicating with which reader. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 30 Active RFID gives greater range. Roles are reversed in this technology. The tag is powered, and emits a signal on a pre-determined schedule, which might typically be one beacon per second. The readers are receivers, typically static, powered and connected to a network. Read range is typically one hundred meters. 3.4.9.2 RFID Frequency A little (recent) history here, the first RFID in common use was LF (Low Frequency). Used for animal tracking, it offered a low read range, typically an inch or two, which was, in this application, sometimes beneficial, as the person using the system had a lot of confidence in knowing which tag was being read. Disadvantages of LF technology included the cost and size of the tag. The tags required many turns of fine wire to transfer energy from the reader to the tag, and this made them expensive to produce, and bulky in appearance. The next generation of tags was HF. These operated at a higher frequency, and required less turns. Tags could now be printed using conventional printed circuit board techniques, but as a complete circuit was required, tags had to use double sided laminate, with a through connection to complete the circuit. Tags were less expensive and less bulky than LF. Range was extended to perhaps twelve inches or so. Typical uses included door entry mechanisms. The next generation of tags was easier tp manufacture, which leads to lower manufacturing costs and potentially smaller tags, though in this case antennae size became critical. The laminate could now be one sided. But antennae size moved up to three or four inches for peak performance. Read range with fixed readers is commonly up to ten or twenty feet, but in some conditions can approach one hundred feet, though this may not be a ""real world" figure 3.4.9.3 Surrounding materials All RFID tags are affected by the materials around them, but the degree to which they are affected depends on the type of tag. Straight passive tags are affected most. These tags have no on board power source, so they rely on energy that they harvest from the reader. If they are close to conductive material, the transfer of power from the reader is disrupted, and the communication with the RFID chip is lost. Conductive materials in this case include metal and water, particularly salty water. The human body contains lots of salty water, so a passive RFID chip help close to the body (or in a pocket or wallet) may be difficult to read. BAP tags are batter assisted power tags. An internal battery provides power, and so they are less affected by adjacent materials (though not totally immune). We are conducting -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 31 tests now with BAP tags, and seeing a higher read rate than with conventional passive tags. Active tags are even less sensitive to surrounding materials, but still not immune. One of our systems uses active RFID tags to track test equipment in a joint development and manufacturing facility. Most equipment is tracked accurately, but occasionally an item is placed "tag side down" on a metal shelf, and becomes invisible to the readers. 3.4.9.4 Tag Type For all frequencies of tag there are different physical configurations. These usually make a tradeoff between size and sensitivity, particularly for UHF tags. We use small "button" tags for some laundry type applications. These have a read range of a few inches. The standard squiggle type tags are about four inches long and offer a much better read range, two or three feet. Encapsulated tags, such as the long blue tags from intermec are more reliable still for longer reads. And some tags have even longer antennae, specifically designed for use in car windscreens. We have read these reliably at a range of sixteen feet with a handheld reader. 3.4.9.5 Type of reader Tags can be read with mobile or fixed readers. For UHF tags, power is provided by the reader, and the tradeoff between range, battery life and antenna size for a mobile reader means that read range is reduced. A typical working range for a mobile handheld reader is up to three feet, again, depending on tag configuration. A fixed mount reader has more power available, and a larger antenna. Read range in normal practical conditions can be up to twenty feet. 3.4.9.6 Orientation The read range around a tag is not spherical. Tags are least sensitive "end on". The pattern of readability is also affected by the antenna of the reader, with circularly polarized antenna providing a shorter range but less reliance on orientation. A linear antenna can give a more impressive read range for a given tag, but turn the reader through ninety degrees, and the tag becomes invisible. 3.4.9.7 Time to read The longer the read time is the better prospect for a read at the extremes of range. This is especially a challenge for portals that try to read many tags on a skid that passes quickly through the portal. A particularly elegant solution is to place the reader on the fork lift truck, so that it has more time to read. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Chapter 3 ‫ـــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e |3 - 32 3.4.9.8 Number of tags being read Not usually a serious problem unless the tag count is very high, but it can have an effect. 3.4.9.9 Density of Tags This can particularly be a problem if small, thin items are to be tracked. Tracking physical file folders is a common application of RFID. This can work well on a pile of folders in use, where the contents spread the tags. But a pile of empty folders, which result in tags being placed back to back, can make the tags at the bottom of the pile difficult to read, as they are in the "shadow" of the tags above them. Conclusion The above might suggest that RFID is unreliable, or perhaps too complicated for practical use. To the contrary, it is a powerful technology for the right application. The above is intended to give some idea of the various factors that can affect the read rate, and which should at least be considered for any given application. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــ‬‫ـــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــ‬‫ـــــــــــــــــــ‬ P a g e | A - 1 Simulation & Results -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــ‬‫ـــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــ‬‫ـــــــــــــــــــ‬ P a g e | A - 2 A. Half wave dipole antenna The geometry of the half wave dipole antenna in free space is shown in Figure A.1.The half wave dipole antenna is a cylinder made of a perfect conductor (PEC). This cylinder has a radius a = 0.5 mm and a height l = 25 cm which is equal to one quarter of the wave length (λ). Between the two PECs, there is a rectangular lumped port which represents the feeding of the antenna. All of those are contained in a vacuum box which represents the radiation pattern of the antenna. Figure A.1: Half wave dipole antenna design in HFSS. Figure A.2: Reflection Coefficient. Length (L) =25cm=λ/4 Diameter d = 1 mm 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00 500.00 Freq [MHz] -15.00 -12.50 -10.00 -7.50 -5.00 -2.50 0.00 dB(S(1,1)) HFSSDesign1XY Plot 1 ANSOFT Curve Info dB(S(1,1)) Setup1 : Sw eep -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــ‬‫ـــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــ‬‫ـــــــــــــــــــ‬ P a g e | A - 3 A.1 Radiation Pattern in different planes 0.80 1.60 2.40 3.20 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1YZ Plane ANSOFT Curve Info rETotal Setup1 : LastAdaptive Freq='0.5GHz' Phi='90deg' 0.80 1.60 2.40 3.20 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1XYPlane ANSOFT Curve Info rETotal Setup1 : LastAdaptive Freq='0.5GHz' Phi='0deg' -25.00 -20.00 -15.00 -10.00 -5.00 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1XZ plane ANSOFT Curve Info dB20normalize(rETotal) Setup1 : LastAdaptive Freq='0.5GHz' Theta='90deg' -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــ‬‫ـــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــ‬‫ـــــــــــــــــــ‬ P a g e | A - 4 B. Printed Dipole antenna The geometry of the Printed dipole antenna in free space is shown in Figure B.1. The Printed dipole antenna is a rectangular made of a perfect conductor (PEC). This rectangular has a Width of 0.1 cm, a length of 11.9 cm. between the two PECs; there is a rectangular lumped port which represents the feeding of the antenna. This antenna is printed on a rectangular substrate. It's a dielectric material (may be silicon dioxide).The geometry of the substrate is as shown in Figure B.1. It has a length of 47 cm, a width of 24 cm and a thickness of 0.5 cm. All of those are contained in a vacuum box which represents the radiation pattern of the antenna. Figure B.1: Printed dipole antenna design in HFSS. Length = 47 cm Width =24 cm Thickness = 0.5 cm Length=11.9 cm Width = 0.1 cm -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــ‬‫ـــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــ‬‫ـــــــــــــــــــ‬ P a g e | A - 5 Figure B.2: Reflection Coefficient. B.1 Radiation pattern in different planes 1.60 3.20 4.80 6.40 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern XZ ANSOFT Curve Info rETotal Setup1 : LastAdaptive Freq='0.5GHz' Theta='90deg' 1.60 3.20 4.80 6.40 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern YZ ANSOFT Curve Info rETotal Setup1 : LastAdaptive Freq='0.5GHz' Phi='90deg' 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern XY ANSOFT Curve Info dB(rETotal) Setup1 : LastAdaptive Freq='0.5GHz' Phi='0deg' 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00 500.00 Freq [MHz] -30.00 -25.00 -20.00 -15.00 -10.00 -5.00 0.00 dB(S(1,1)) HFSSDesign1XY Plot 1 ANSOFT Curve Info dB(S(1,1)) Setup1 : Sw eep -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 1 RFID Chip Tag Analysis -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 2 Commonly antennas are designed to match to a substantially real load in order to minimize the standing waves along the feeding transmission line. However, for RFID antennas, the load is in close proximity to the antenna and also reactive. Therefore, in order to improve the tag performance the power transferred to the load must be maximized. Let Za= Ra+ j Xa and ZC = RC + j XC are the antenna and chip complex impedances respectively. Maximum power transfer occurs when Za=ZC * . The power transfer efficiency is the ratio of the actual power transferred to the maximum possible power transferred. Eq. 1𝝉 = 𝟒𝐑 𝐜 𝐑 𝐚 | 𝐑 𝐜+𝐑 𝐚| 𝟐 A power wave reflection coefficient can be defined as: 𝓣𝐭𝐚𝐠 = 𝐙 𝐜−𝐙 𝐚 ∗ 𝐙 𝐜+𝐙 𝐚 Eq.2 The maximum read range of the tag along the (θ, φ) direction, is computed from Friis free‐space formula as 𝐑 = 𝛌 𝟒𝛑 √ 𝐏𝐭 𝐆 𝐭 𝐆 𝐫 𝐩 𝐏 𝐭𝐡 Eq.3  where λ is the wavelength, Pt is the power transmitted by the reader, Gt is the gain of the transmitting reader antenna, Gr is the gain of the receiving tag antenna, Pth is the minimum threshold power necessary to provide enough power to the RFID tag chip which is equal to ‐12dBm in this case, p is the polarization mismatch factor and τ is power transmission coefficient. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 3 Numerical Results UHF tag models A.First model The geometry of the spiral RFID tag antenna in free space is shown in Figure A. Antenna structure consists of FR4‐ epoxy substrate of relative permittivity εr =4.4, tan δ=0.02 and has a dimension of Ls × Ws × Hs = 70 × 57.6 × 1 mm3 with printed spiral shaped microstrip dipole of dimensions La × Wa where Wa = 4mm and values of La are shown in table A. Table A L11L10L9L8L7L6L5L4L3L2L1 2.76 cm 0.7 cm 3.36 cm 1.3 cm 3.96 cm 1.9 cm 4.56 cm 2.5 cm 5.16 cm 3.1 cm 2.58 cm Figure A -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 4 First, the antenna dimensions are optimized in free space for conjugate matching with the RFID/ASIC chip having an input impedance ZC =25 – j 100 Ω at 915MHz at minimum received power of -12 dBm The IC-microchip is placed in the center of the design as shown. The radiation characteristics of the proposed tag antenna including the antenna input impedance, chip impedance, the reflection coefficient, the power transmission coefficient, the antenna gain and the read range as functions of frequency for the planar RFID tag antenna in free space are shown in Figures A.1. The antenna input impedance and the chip impedance are shown in Figure A.1.1. Figure A.1.1: The tag antenna input impedance (Ra, Xa) and chip impedance (RC, XC). The antenna input impedance is conjugate matched with the IC- microchip capacitive impedance at resonance frequency of 915 MHz resulting in impedance matching band, where the band width is 36 MHz (908-944 GHz). Good impedance matching is obtained with -68 dB reflection coefficient as shown in Figure A.1.2. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 5 Figure A.1.2: The reflection coefficient. Thus high power transmission is occurred at the resonance frequency as depicted from the variation of the power transmission coefficient ratio shown in Figure A.1.3. Figure A.1.3: The power transmission. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 6 The gain variation versus frequency is shown in Figure A.1.4. Figure A.1.4: The antenna gain. The antenna gain (as a ratio) is 1.62 at 915 GHz. Using the read range equation given by eq. 3 the RFID tag gives maximum read range of 7.8 m at the resonance frequency of 915 as shown from Figure A.1.5. Figure A.1.5: The tag antenna read range. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 7 The simulated radiation patterns in different planes at the resonance frequency (f = 915 GHz) are plotted in Figures A.2 for the planar RFID tag antenna in free space. An Omni- directional radiation pattern is obtained in x-z plane at f = 915 MHz which meets the RFID system. Figure A.2.1: Radiation pattern in x-y plane. Figure A.2.2: Radiation pattern in y-z plane. Figure A.2.2: Radiation pattern in x-z plane. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 8 B. Second model In this design the size is reduced to half. Where one of the two arms of spiral shaped microstrip dipole is printed at the top of FR4-epoxy substrate and the other one is printed on the bottom of the substrate. Geometry of the spiral RFID tag antenna in free space is shown in Figure B. Antenna structure consists of FR4-epoxy substrate of relative permittivity εr =4.4, tan δ=0.02 and has a dimension of Ls × Ws × Hs = 30 × 31.5 × 1 mm3 with printed spiral shaped microstrip dipole of dimensions La × Wa where Wa=3mm and values of La are shown in table B. L11L10L9L8L7L6L5L4L3L2L1 7.5 mm 6 mm 12.5 mm 11 mm 17.5 mm 16 mm 22.5 mm 21 mm 27.5 mm 26 mm 14.7 mm Table B Figure B -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 9 First, the antenna dimensions are optimized in free space for conjugate matching with the RFID/ASIC chip having an input impedance ZC = 10 – j150 Ω at 915MHz at minimum received power of -10 dBm The IC-microchip is placed in the center of the design as shown in Figure B . Figure B The radiation characteristics of the proposed tag antenna including the antenna input impedance, chip impedance, the reflection coefficient, the power transmission coefficient, the antenna gain and the read range as functions of frequency for the planar RFID tag antenna in free space are shown in Figures B.1. The tag antenna input impedance and chip impedance are shown in Figure B.1.1. Figure B.1.1: The tag antenna input impedance (Ra, Xa) and chip impedance (RC, XC). The IC microstrip Ls Xa Xc H -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 10 The antenna input impedance is conjugate matched with the IC- microchip capacitive impedance at the two resonance frequency of 915 MHz resulting in impedance matching band, where the band width is 36 MHz (908 - 944 GHz) good impedance matching is obtained in this band width -68dB reflection coefficient as shown in Figure B.1.2. Figure B.1.2: The reflection coefficient. Thus high power transmission is occurred at the resonance frequency as depicted from the variation of the power transmission coefficient ratio shown in Figure B.1.3. Figure B.1.3: The power transmission. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 11 The gain variation versus frequency is shown in Figure B.1.4. Figure B.1.4: The antenna gain. The antenna gain (as a ratio) is 1.62 at 915 GHz. Using the read range equation given by eq. 3 the RFID tag gives maximum read range of 4.9 m at the resonance frequency of 915 as shown from Figure B.1.5. Figure B.1.5: The tag antenna read range. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 12 ` Figure B.2.1: Radiation pattern in x-y plane. Figure B.2.2: Radiation pattern in y-z plane. Figure B.2.3: Radiation pattern in x-z plane. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 13 Microwave tag models The advantage in those models is that the operating frequency is in the microwave range resulting in avoiding interference with other applications like mobile applications. A. First model The geometry of the butterfly RFID tag antenna in free space is shown in figure A. Figure A antenna structure consists of a paper substrate of relative permittivity εr =3.85,and has a dimension of L× W =40×35 mm2 and the thickness of H=70µm with printed butterfly shaped micro strip dipole of dimensions L1×W1 are shown in table A. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 14 Table A First, the antenna dimensions are optimized in free space for conjugate matching with the RFID/ASIC chip having an input impedance ZC = 40 ‐ j94 Ω at 915 MHz at minimum received power of ‐12 dBm , The IC‐microchip is placed in the center of the design as shown in Figure A. The radiation characteristics of the proposed tag antenna including the antenna input impedance, chip impedance, the reflection coefficient, the power transmission coefficient, the antenna gain and the read range as functions of frequency for the planar RFID tag antenna in free space are shown in Figure A.1.1. Figure A.1.1: The tag antenna input impedance (Ra, Xa) and chip impedance (RC, XC). -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 15 The antenna input impedance is conjugate matched with the IC‐microchip capacitive impedance at the two resonance frequency of 2.45 GHz resulting in impedance matching band, where the band width is 200 MHz (2.3‐2.5 GHz) good impedance matching is obtained in this band width ‐41.6 dB reflection coefficient as shown in Figure A.1.2. Figure A.1.2: The reflection coefficient. Thus high power transmission is occurred at the resonance frequency as depicted from the variation of the power transmission coefficient ratio shown in Figure A.1.3. Figure A.1.3: The power transmission. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 16 The gain variation versus frequency is shown in Figure A.1.4. Figure A.1.4: The antenna gain.  The antenna gain (as a ratio) is 2.67 at 2.45 GHz. Using the read range equation given by eq. 3 the RFID tag gives maximum read range of 2.64 m at the resonance frequency of 2.45 GHz as shown from Figure A.1.5. Figure A.1.5: The tag antenna read range. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 17 The simulated radiation patterns in different planes at the resonance frequency (f =2.45 GHz) are plotted in Figures A.2 for the planar RFID tag antenna in free space. An Omni directional radiation pattern is obtained in x‐z plane at f=2.45 GHz which meets the RFID system. Figure A.2.1: Radiation pattern in x‐y plane. Figure A.2.2: Radiation pattern in y‐z plane. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 18 .Figure A.2.3: Radiation pattern in x‐z plane -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 19 B.Second model The geometry of the smart card RFID tag antenna in free space is shown in figure B. Figure B Antenna structure consists of a paper substrate of relative permittivity εr =3.85, and has a dimension of L × W = 3×7.8 cm2 and a thickness of H = 70µm.  First, the antenna dimensions are optimized in free space for conjugate matching with the RFID/ASIC chip having an input impedance ZC =12 ‐ j300 Ω at 915 MHz at minimum received power of ‐12 dBm , The IC‐microchip is placed in the center of the design as shown in Figure B. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 20 The radiation characteristics of the proposed tag antenna including the antenna input impedance, chip impedance, the reflection coefficient, the power transmission coefficient, the antenna gain and the read range as functions of frequency for the planar RFID tag antenna in free space are shown in Figure B.1.1. Figure B.1.1: The tag antenna input impedance (Ra, Xa) and chip impedance (RC, XC). The antenna input impedance is conjugate matched with the IC‐microchip capacitive impedance at the two resonance frequency of 2.45 GHz resulting in impedance matching band, where the band width is 200 MHz (2.3‐2.5 GHz) good impedance matching is obtained in this band width ‐40.42 dB reflection coefficient as shown in Figure B.1.2. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 21 Figure B.1.2: The reflection coefficient. Thus high power transmission is occurred at the resonance frequency as depicted from the variation of the power transmission coefficient ratio shown in Figure B.1.3. Figure B.1.3: The power transmission. The gain variation versus frequency is shown in Figure B.1.4. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 22 Figure B.1.4: The antenna gain.  The antenna gain (as a ratio) is 11.08 at 2.45 GHz. Using the read range equation given by eq. 3 the RFID tag gives maximum read range of 6.3 m at the resonance frequency of 2.45 GHz as shown from Figure B.1.5. Figure B.1.5: The tag antenna read range. The simulated radiation patterns in different planes at the resonance frequency (f =2.45 GHz) are plotted in Figures B.2 for the planar RFID tag antenna in free space. An Omni directional radiation pattern is obtained in x‐z plane at f=2.45 GHz which meets the RFID system. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • RFID Chip Tag Analysis ‫ـــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــ‬‫ـــــ‬ P a g e | B - 23 Figure B.2.1: Radiation pattern in x‐y plane. Figure B.2.2: Radiation pattern in y‐z plane. Figure B.2.3: Radiation pattern in x‐z plane. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 1 4 RFID CHIP-LESS TAG 4.1 Introduction The Chip less RFID tags do not contain a chip or electronic circuit, and thus store information purely in the electromagnetic materials which comprise the tag. Since the absence of an electronic circuit makes it more difficult to store information in a compact area, chip less RFID tags are generally limited to a data capacity of less than 32 bits, although in some cases more bits are possible. For many applications, such as identifying classes of objects, a large ID string is not necessary. In this case, where only a few dozen or a few hundred different IDs are required, a chip less RFID can be used. 4.2 Difficulties of achieving low cost RFID Instead of optical barcodes has not yet been achieved due to the greater price of the RFID tag (10 cents) compared to the price of the optical barcode(less than 0.1 cents) Application Specific Integrated Circuit (ASIC) design and testing along with the tag antenna and ASIC assembly result in a costly manufacturing process. This is why it is not possible to further lower the price of the chipped tag. 4.3 Definition of Chip less RFID tag Design low cost RFID tags without the use of traditional silicon ASICs have emerged these tags, and therefore systems, are known as chip less RFID systems. 4.4 Specifications for chip less RFID tag 4.4.1 Electrical specifications Frequency of operation 3.1–10.7 GHz Tag antenna polarization Linearly polarized Tag antenna radiation Preferably Omni-directional Number of bits Greater than 20 bits -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 2 4.4.2 Mechanical specifications Tag Size Width: 64 mm maximum ; Length: 120 mm Printability Fully printable, no semiconductor Operations Printed on thin plastic/paper objects Weight Less than 5g Visibility Preferably transparent Operating temperature –20° to 80°C 4.4.3 Commercial Cost Less than 1 cent per tag. 4.5 Operation of the chip less RFID We present here a fully printable chip less RFID system based on multiresonators and cross-polarized ultra-wideband monopole antenna. The tag’s unique ID is encoded as the spectral signatures of the resonators. The chip less RFID system works on retransmission of the interrogation signal with the encoded unique spectral ID. The received and transmitted signals are cross- polarized in order to achieve good isolation between the two. As the chip less RFID system uses spectral signatures for data encoding and is fully passive, the tags do not need any power supply in order to operate. From the figure we see that the chip less tag encodes data in the frequency spectrum and thus has a unique ID of spectral signatures. The spectral signature is obtained by interrogating the tag by a continuous wave (CW) multi-frequency signal of uniform amplitude and phase. The tag then receives the interrogation signal and encodes the data into the frequency spectrum in both magnitude and phase. The encoded signal is then retransmitted back to the reader. This allows the reader to use two criteria for data decoding amplitude and phase. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 3 4.6 Types of Chip less RFID tag 4.6.1 TDR-based chip less RFID tags Are interrogated by sending a signal from the reader in the form of a pulse and listening to the echoes of the pulse sent by the tag. A train of pulses is created which can be used to encode data. Various RFID tags have been reported using TDR-based technology for data encoding. 4.6.1.1 Non-Printable Chip less RFID tag The interrogation pulse is converted to a surface acoustic Wave using an interdigital transducer (IDT). The surface acoustic wave propagates across the piezoelectric crystal and is reflected by a number of reflectors which create train of pulses with phase shifts. The train of pulses converted back to an EM wave using the IDT and detected at the reader end where the tag’s ID is decoded. 4.6.1.2 Printable TDR-based Chip-less tags can be found either as Thin-Film-Transistor-Circuits (TFTC) or micro strip-based tags with discontinuities. TFTC tags are printed at high speed on low cost plastic film. TFTC tags offer advantages over active and passive chip-based tags due to their small size and low power consumption. They require more power than other chip-less tags but offer more functionality. However low cost manufacturing processes for TFTC tags have not yet been developed. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 4 4.6.1.2.1 Delay-line-based Chip-less RFID tags operate by introducing a micro strip discontinuity after section of delay-line. The tag is excited by a short pulse (1ns) EM signal. The interrogation pulse is received by the tag and reflected at various points along the micro strip line creating multiple echoes of the interrogation pulse. The time delay between the echoes is determined by the length of the delay- line between the discontinuities. This type of tag is a replica of the SAW tag using micro strip technology which makes it printable. Although initial trials of and experiments on this Chip less technology have been reported, only 4 bits of data have been successfully encoded. 4.6.2 Spectral signature-based chip less tags Encode data into the spectrum using resonant structures. Each data bit is usually associated with the presence or absence of a resonant peak at a predetermined frequency in the spectrum. So far, five types of spectral signature based tags have been reported and all five are considered to be fully printable. 4.6.2.1 Chemical tags Are designed from a deposition of resonating fibers or special electronic ink. 4.6.2.1.1 Nano-metric materials These tags consist of tiny particles of chemicals which exhibit varying degrees of magnetism and when electromagnetic waves impinge on them they resonate with distinct frequencies, which are picked up by the reader. They are very cheap and can easily be used inside banknotes and important documents. 4.6.2.1.2 Ink-tattoo chip less tags Use electronic ink patterns embedded into or printed onto the surface of the object being tagged. Electronic ink is deposited in a unique barcode pattern which is different for every item. The system operates by interrogating the ink- tattoo tag by a high frequency microwave signal (>10 GHz) and is reflected by areas of the tattoo which have ink creating a unique pattern which can be detected by the reader. The reading range is claimed to be up to 1.2 m (4 feet). In the case of animal ID, the ink is placed in a one-time-use disposable cartridge. For non-animal applications the ink can be printed on plastic/paper or within the material. Based on the limited information available for this technology (which is still in the experimental phase) the author assumes that it is spectral signature based. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 5 4.6.2.2 Planar circuit chip less RFID Are designed using standard planar micro strip/co-planar waveguide/strip line resonant structures such as antennas, filters, and fractals? They are printed on thick, thin and flexible laminates and polymer substrates. 4.6.2.2.1 Capacitive tuned dipoles The chip less tag consists of number of dipole antennas which resonate at different frequencies. When the tag is interrogated by a frequency sweep signal the reader looks for magnitude dips in the spectrum as a result of the dipoles. Each dipole has a 1:1 correspondence to a data bit. Issues regarding this technology include: tag size (lower frequency longer dipole – half wavelength) and mutual coupling effects between dipole elements. 4.6.2.2.2 Space-filling curves The tags are designed as Peano and Hilbert curves with resonances centered around 900 MHz .The tags represent a frequency selective surface (FSS)which is manipulated with the use of space-filling curves (such as the Hilbert curve). The tag was successfully interrogated in an anechoic chamber. Only 3 bits of data have been reported to date. However, the tag requires significant layout modifications in order to encode data. 4.6.2.2.3 LC Resonant Chip-less tag comprise of a simple coil which is resonant at a particular frequency. These tags are considered 1-bit RFID tags. The operating principle is based on the magnetic coupling between the reader antenna and the LC resonant tag. 4.7 Chip less RFID tag The chip less RFID tag consists of UWB antennas and a multiresonating circuit operating in the UWB frequency spectrum as shown in Fig below. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 6 The UWB antennas are used to receive the interrogation signal sent from the reader and transmit the signal back to the reader after performing spectral signal modulation by the multiresonator. The multiresonator is a combination of multiple filtering sections which are used to modulate the spectrum of the interrogation signal sent by the reader. Modulation is performed in both magnitude and phase of the spectrum. Modulation in the spectrum 4.8 Spiral Resonators The spiral resonator is one of the main components of the chip-less RFID tag, which is used to encode data into the tag’s spectral signature. A parametric study of the spiral resonator’s different layout parameters is conducted in order to design the most optimal spiral resonator. Spiral resonators are developed in micro strip and coplanar waveguide technology. Coplanar waveguide technology provides superior performance on thinner laminates. A novel data encoding technique using spiral shorting is presented. Finally, a multiresonating circuit comprised of cascaded spiral resonators used to encode data into the spectral signature is designed and optimized. 4.9 Theoretical Modeling of Spiral Resonator The layout of a conventional spiral resonator, the micro strip line and the spiral resonator are on the same plane (top layer) and are separated from the continuous metallic ground plane (bottom layer) by a dielectric layer. The surface current distribution simulation is used in order to understand how the stop-band effect is created at the spiral’s resonant frequency. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 7 Figure shows (a) The peak surface current distribution of a spiral resonator at its resonant frequency (2 GHz) and (b) At a non-resonant frequency (2.1 GHz). The simulation was performed using CST Microwave Studio 2008. From Fig it is clear that the surface current distribution is greater around the spiral at its resonant frequency. The spiral resonator creates a low impedance path to ground at its resonant frequency and absorbs the majority of the current propagating from Port 1 to Port 2 of the micro strip line resulting in a stop- band effect. 4.10 Spiral Resonator Modeling Using Distributed Components The spiral resonator coupled to a micro strip line can be modeled using distributed capacitance and inductance as a series RLC circuit coupled to a micro strip line. The spiral resonator on its own is modeled as a series RLC circuit due to the low impedance path that it creates at its resonant frequency, which is the characteristic of series RLC circuits. When the spiral resonator is coupled to -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Chapter 4RFID Chip-less Tag ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 4 - 8 the micro strip line, the entire circuit (micro strip line + gap coupling + spiral resonator) is modeled as a parallel RLC due to its stop-band characteristic as reported in ref. The spiral resonator is modeled as a series RLC circuit, where the distributed capacitance is CD, the distributed inductance is LD and the resistive loss of the spiral is RD. The coupling between the micro strip line and the spiral resonator is modeled with mutual inductance LM, which is determined by the length of the coupled line and the distance from the 50 Ω lines. 4.11 Ultra Wideband Antennas Chip less RFID tags require a significant amount of spectrum in order to encode their data. Hence, ultra wideband antennas seem like the obvious solution as the antenna of choice for the chip less RFID tag. The theory of operation and parametric study of circular disc monopole antennas printed on dielectric laminates is presented. Finally, an optimized monopole antenna for operating in the UWB spectrum is presented. The RFID reader antennas are also presented. The RFID reader requires a high gain antenna; hence, log periodic dipole antenna arrays on Taconic laminate are designed. The LPDA exhibits high gain, a directive radiation patterned wide-operating bandwidth. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | C - 1 Simulation & Results -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | C - 2 A. Chip-less Tag (Bars) The geometry of the rectangular chip-less tag design in free space is shown in Figure A.1. The rectangular chip-less tag is made of five rectangulars made of a perfect conductor (PEC). These rectangular are in the same width = 3mm, but in different length = 5.3 cm, 5.2 cm, 5.1 cm, 5 cm and 4.9 cm. This tag antenna is fixed on a rectangular dielectric substrate like paper. The geometry of the substrate is as shown in Figure A.1. It has a length of 5.5 cm, a width of 0.5 cm and it's very thin about 50 µm. Figure A.1: HFSS design of a rectangular Chip-less Tag. Width = 0.5 cm Length = 5.5 cm w 5L4L3L2L1L  W = 3 mm  L1 = 5.3 cm  L2 = 5.2 cm  L3 = 5.1 cm  L4 = 5 cm  L5 = 4.9 cm -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | C - 3 Figure A.2: RADAR Cross section (RCS). A.1 Variation of Frequency with length 2.30 2.35 2.40 2.45 2.50 2.55 2.60 2.65 Freq [GHz] -19.50 -19.00 -18.50 -18.00 -17.50 -17.00 -16.50dB(RCSTotal) HFSSDesign1XY Plot 1 ANSOFT Curve Info dB(RCSTotal) Setup1 : Sweep Phi='0deg' Theta='0deg' -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | C - 4 B. Chip-less Tag (Ellipse) The geometry of the Ellipse chip-less tag design in free space is shown in Figure B.1. The ellipse chip-less tag is made of five ellipses made of a perfect conductor (PEC). These ellipses are in different minor and major radius as shown in the figure so that each will give a different resonance frequency than others. This tag antenna is fixed on a rectangular dielectric substrate like paper. The geometry of the substrate is as shown in Figure B.1. It has a length of 7.5 cm, a width of 2.6 mm and a thickness of 50 µm. Figure B.1: HFSS design of Ellipse Chip-less Tag. Length = 7.5Cm Width = 2.6 Cm Thickness = 50 µm 1D 2D 4D 3D 5D = 1.2 cm1D = 1.1 cm2D = 1 cm3D = 0.9 cm4D = 0.8 cm5D -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | C - 5 Figure B.1: RADAR Cross section (RCS). B.1 Variation of Frequency with length 3.00 3.25 3.50 3.75 4.00 4.25 4.50 Freq [GHz] -22.50 -21.25 -20.00 -18.75 -17.50 -16.25 -15.00 dB(RCSTotal) HFSSDesign1XY Plot 1 ANSOFT Curve Info dB(RCSTotal) Setup1 : Sw eep Phi='0deg' Theta='0deg' -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 1 5 Modern RFID Readers 5.1 Introduction RFID readers are devices that perform the interrogation of RFID transponders. In a chip-less RFID system, the RFID reader detects the tag by using signal processing demodulation techniques to extract data from the transponder's signal. A chip-less tag cannot generate a signal without the reader sending an interrogation signal to the transponder. Therefore, the reader and transponders are in a master–slave relationship, where the reader acts as a master and the transponders as slaves. Nevertheless, RFID readers themselves are in a slave position as well. A software application, also called middleware, processes data from the RFID reader, acts as the master unit and sends commands to the reader as shown in Figure 5.1. Figure 5.1: Master–slave principle between the application software and reader, and the reader and transponders. 5.2 RFID Reader Architecture Received Data Digital section RF section Host application with middleware Transmitt _ed Data Reader antenna Figure 5.2: RFID Reader Architecture -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 2 An RFID reader consists of three main parts as shown in Fig. 5.2. These main three components are: 1) Digital/control section. 2) RF section. 3) Antenna. The digital section of the RFID reader performs digital signal processing over the received data from the RFID transponder. This section usually consists of a microprocessor, a memory block, a few analogue-to-digital converters (ADCs) and a communication block for the software application. The reader’s RF section is used for RF signal transmission and reception and consists of two separate signal paths to correspond with the two directional data flows as shown in Figure 5.3. Figure 5.3: Block diagram of RF section of RFID system. The local oscillator generates the RF carrier signal, a modulator modulates the signal, the modulated signal is amplified by the power amplifier, and the amplified signal is transmitted through the antenna. A directional coupler separates the system’s transmitted signal and the received weak back-scattered signal from the tag. The weak back-scattered signal is amplified using low noise amplifiers (LNA) before the signal is decoded in the demodulator, Different demodulation techniques are used when decoding the data received from the transponder. Most RF sections are protected from EM interference using metal cages. Depending on the RFID system’s applications, the RFID reader can be designed in different ways, where the antenna’s resonating frequency, gain, directivity and radiation pattern can vary. Adaptive antennas act as spatial filters and a promising technique for implementing this spatial diversity into RFID readers. The antenna reported in ref. is a 5-element rectangular patch antenna array with an intelligent beam -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 3 forming network at 2.45 GHz. A number of different reader antennas have been developed during the years based on micro strip patch antennas. Following is a detailed discussion on various RFID reader systems available in the market and reported in open literature. 5.3 Review of RFID Readers Figure 5.4 shows the classifications of RFID readers available in open literature and commercial markets. The classification is done after an analysis and synthesis of a comprehensive literature review on RFID readers. The classification is based on the power supply, communication interface, mobility, tag interrogation, frequency response and the supporting protocols of the reader .The classification of the RFID reader based on their power supply brings fort two types of readers: readers supplied from the power network and battery- powered (BP) readers. Readers supplied by the power network generally use a power cord connected to an appropriate external electrical outlet. Most readers that use this type of power are shown in Figure 5.4. Classification of RFID readers available in the market and open literature supply are fixed stationary readers and their operating power supply. Figure 5.4: Classification of RFID readers available in the market and open literature. Ranges from 5 to 12 V, but there are examples of readers that operate at voltage levels as high as 24 V. Battery-powered readers are light in weight and portable. The battery is mainly used to power up the motherboard of the reader. Most BP readers are hand- held, but there are stationary readers that are battery assisted as well. BP readers use from 5 V up to 12 V batteries for their power supply. Based on their communication interface, readers can be classified as serial and network. Serial readers use a serial communication link to communicate with their host computers or software applications. The reader is physically -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 4 connected to a host computer using the RS-232, RS-485, I2C or USB serial connection. Network readers are connected to the host computer via a wired or wireless network. These types of readers behave like a standard network device. Today’s RFID readers support multiple network protocols, such as Ethernet, TCP/IP, UDP/IP, HTTP, LAN, WLAN and others. This allows easier tracking, maintenance, data rate and results in a smaller number of hosts for installing a large number of readers in comparison with serial readers. The next classification of RFID readers can be made on their mobility. Hence, we distinguish two types of readers: stationary and hand-held RFID readers. Stationary RFID readers are also known as fixed readers. This term comes from the reader’s ability to be mounted on walls, portals, doors or other objects, where they can perform effective transponder readings and are not meant to be moved or carried. Fixed RFID readers are mainly used for wireless data capture in supply chain management, asset tracking and product control, but can also be found in personnel identification and authentication for restricted access areas as well. Hand-held RFID readers are mobile readers that can be carried and operated by users as hand-held units. Hand-held readers have built-in antennas and usually don't have connectors for additional antennas. They are BP and are light weight (from82 g up to 700 g). They have shorter reading ranges than fixed readers and are mainly used for tracking live stock, locating items in stores and in stock, etc. Another classification of RFID readers can be made upon the reader’s interrogation protocols in terms of being passive and active. Passive readers are limited to only “listening” and do not perform additional tag interrogations. When interrogating the tags, the reader sends CW signal as a power source for the RFID transponder, which becomes activated. Upon activation, the RFID transponder transmits its unique ID back to the reader. Active readers are true interrogators, which interrogate and listen to tags. Active readers perform data transmission towards the tags, which is implemented, in most cases, as a modulation of the carrier signal. Therefore, transponders must have a demodulating circuitry enabling them to decode the reader’s command. These readers can perform both listening and calling out to the tags and can even achieve successful area location of the transponder based on the amplitudes of the transponders respond to the reader’s interrogation. We can classify readers based on the transponder frequency responses that they listen to as unique frequency response and non-unique frequency response- based readers. Unique frequency response-based readers operate at a unique (or short bandwidth < 80 MHz) frequency range and use this frequency for both data transmission and reception. The vast majority of RFID readers that can be found on the market today are unique frequency response-based readers. None-unique frequency response-based readers operate using one frequency for sending a command or just provide a carrier signal at a certain frequency and listen for an integer multiple of its carrier frequency, generally in the form of a -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 5 second harmonic, or a frequency-divided signal as the transponder’s response . Two RF frequencies used for communication by the reader to the RFID system allow fast and reliable full-duplex communication, but this system needs a more complex RF front end for both the reader and transponder module. Figure 5.5 shows a multi-frequency RFID system. We can distinguish between two types of RFID readers based upon their ability to communicate with transponders in regards to data-encoding protocols: simple RFID readers and agile RFID readers. Figure 5.5 shows System-level overview of the Range Master-embedded RFID reader. Simple RFID readers use a unique protocol for communication and data transmission between transponders in the reader’s interrogation zone. When a transponder that supports the reader’s interrogation protocol is set in the interrogation area of the reader, the tag is automatically recognized and detected. When a transponder that operates using a different protocol is put into the interrogation area, no data transmission will occur because of the unfamiliarity of the reader’s interrogation protocol to the transponder. Agile RFID readers can operate and perform interrogations and data transmission with transponders using multiple protocols. The most commonly used protocols for data transmission between transponders and readers are EPC Gen1, EPC Gen2, ISO 18000, TIRIS Bus Protocol, etc. The majority of RFID readers that can be found in the market are designed for multiple protocols and multi-tag readings. Figure 5.5: System-level overview of the Range Master embedded RFID reader. Range Master Chipset RFID dpASP RFID state machine Voltage limit down converter and LNA ON/OFF Modulator RFID reader system controller TX/RX software stake -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 6 We can distinguish between two types of RFID readers based on their antennas fixed beam RFID readers and scanned array RFID readers.  Fixed beam antennas are characterized with a unique and fixed beam radiation pattern. The use of several fixed beam antennas is used as well and can be commonly found in Alien Technology readers. The advantage of using such antennas is that they are easy to install and do not need any logic to control their radiation patterns. The disadvantage of these antennas is that they pick up multipath signals alongside with the transponders signal, which can result in errors during interrogation.  Scanned Array RFID readers use smart antenna systems in order to reduce the number of transponders within their main lobe radiation zone, thus reduce reading errors and collisions among tags. This technique exploits spatial diversity among tag’s locations. The direct beam also reduces the effects of multipath. This new approach to RFID antenna technology is being incorporated by a few RFID manufacturers, such as Omron Corporation, Japan, RFID Inc, RFSAW, and USA. 5.4 Towards Universal Reader Design RFID reader designers and manufacturers have gone a step further in the design of independent reader modules. The design of embedded RFID reader has been introduced to the world of RFID in 2005. In June 2005, Anadigm Inc., announced the birth of the industry’s first RFID-embedded reader that can be customized to read different RFID tag types, with different modulation schemes, frequencies and data transmission protocols. The “universal” reader is named Range Master. The Range Master’s system-level block diagram is shown in Figure 5.5. It comprises a Field Programmable Analogue Array (FPAA) in conjunction with an RFID State Machine, enabling RFID system engineers to develop a universal RFID reader supporting multiple protocols and frequencies for future fixed, mobile and hand-held reader designs. The advantage of embedded RFID readers, such as Range Master, when compared to standard readers is that they allow standardization around a single circuit board, simplification and improvement of product development, manufacturing time and cost. 5.5 Proposed Chip-less RFID System The proposed chip-less RFID system uses spectral signatures for data encoding and is fully passive, hence the tags do not need any power supply in order to operate. The main application for this chip-less RFID system is mainly short ranged (up to 40 cm) tagging of extremely low cost items. Hence, power limitation restrictions (transmitted EIRP maximum of - 45 dBm outdoors and - 55 dBm indoors) do not present a major concern for the proposed system. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 7 The principal block diagram of the proposed chip-less RFID system is shown in Figure 5.6. As can be seen in Figure 5.6, the chip-less tag encodes data in the frequency spectrum hence having a unique ID of spectral signatures. The spectral signature is obtained by interrogating the tag by a continuous wave (CW) multi-frequency signal of uniform amplitude and phase. The tag then receives the interrogation signal and encodes the data into the frequency spectrum in both magnitude and phase. The encoded signal is then retransmitted back to the reader. This allows the reader to use two criteria for data decoding amplitude and phase. The chip-less RFID tag consists of UWB antennas and a multiresonating circuit operating in the UWB frequency spectrum as shown in Figure 5.7. The UWB antennas are used to receive the interrogation signal sent from the reader and transmit the signal back to the reader after performing spectral signal modulation by the multiresonator. The multiresonator is a combination of multiple filtering sections, which are used to modulate the spectrum of the interrogation signal sent by the reader. Modulation is performed in both magnitude and phase of the spectrum. Figure 5.6: Principle Block Diagram of proposed chip-less RFID system. Figure 5.7: Block diagram of proposed chip-less RFID tag. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 8 Figure 5.8: Block diagram of proposed chip-less RFID reader. The magnitude and phase are modulated in the forms of magnitude attenuations and phase jumps at the resonant frequencies of the multiresonator, respectively. The chip-less RFID reader is an electronic device, which can detect the ID of the chip-less tag once it is within the reader’s interrogation zone. The block diagram of the chip-less RFID reader and its basic components are shown in Figure 5.8. The RFID reader has transmitting and receiving antennas for sending the interrogation signal to the chip-less tags and receiving the encoded signal from the chip-less tag, respectively. The RFID reader transmitter comprises a voltage controlled oscillator (VCO), low noise amplifier (LNA), and power amplifier (PA). Tuning of the VCO’s output frequency is done by the microcontroller through the digital-to-analog (ADC) converter. The reader transmitter generates the interrogation signal, which is sent to the chip-less tag. The chip-less transponder encodes its spectral signature into the reader's interrogation signal and sends the signal back to the reader. The signal processing of the received tag signal is performed at the receiver end of the RFID reader and results in a digital signal being sent to the microprocessor of the RFID reader. The receiver comprises an LNA, a band-pass filter (BPF), a demodulating circuit which converts the RF signal to baseband, and an analog-to-digital converter. The microprocessor uses tag detection and decoding algorithms to determine the ID of the chip-less tag. This data is sent to an application or software enterprise on a PC, which provides the graphical user interface between the RFID system and the user. 5.6 Review of Chip-less RFID Transponders There have been a few reported chip-less RFID tag developments in recent years (Table 5.1). However, most of them are still reported as prototypes and only a handful is considered to be commercially viable or available. The -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 9 challenge that researchers face when designing chip-less RFID transponders is how to perform data encoding without the presence of a chip. In response to this problem, two general types of RFID transponders can be identified: time domain reflectometry (TDR)-based and spectral (frequency) signature-based chip-less RFID transponders. Figure 5.9 shows the classification of reported chip-less RFID transponders. TDR-based chip-less RFID transponders are interrogated by sending a signal by the reader in the form of a pulse and listening to the echoes of the pulse sent by the tag. This way a train of pulses is created, which can be used to encode data. Various RFID transponders have been reported using TDR-based technology for data encoding. We can distinguish between non-printable and printable TDR-based transponders Table 5.1: Specifications for chip-less RFID tag ----------------------------------------------------------------------------------------------- Electrical specifications Frequency of operation 3.1–10.7 GHz Tag antenna polarization linearly polarized Tag antenna radiation preferably Omni-directional Number of bits Greater than 20 bits Mechanical specifications Tag Size Width: 64 mm maximum; Length: 120 mm Printability Fully printable, no semiconductor Operations Printed on thin plastic/paper objects Weight Less than 5g Visibility Preferably transparent Operating temperature –20° to 80°Commercial Cost Less than 1 cent per tag. ----------------------------------------------------------------------------------------- Figure 5.9: classification of chip-less RFID transponder. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 10 The example of a non-printable TDR-based chip-less RFID transponder is the surface acoustic wave (SAW) tag, which is also the commercially most successful developed by RFSAW Inc . SAW tags are excited by a chirped Gaussian pulse sent by the reader centered around 2.45 GHz. The interrogation pulse is converted to a SAW using an inter digital transducer (IDT). The SAW propagates across the piezoelectric crystal and is reflected by a number of reflectors, which creates a train of pulses with phase shifts. The train of pulses is converted back to an EM wave using the IDT and detected at the reader end, where the tag’s ID is decoded. Printable TDR- based chip-less transponders can be found either as Thin-Film- Transistor Circuits (TFTC) or micro strip-based transponders with discontinuities. TFTC transponders are printed at high speed and on low cost plastic film. TFTC tags offer advantages over active and passive chip-based transponders due to their small size and low power consumption. They require more power than other chip-less tags, but offer more functionality. However, low cost manufacturing processes for TFTC tags have not been developed yet. Another issue is the low electron mobility, which limits the frequency of operation up to several MHz Delay-line based chip-less RFID tags operate by introducing a micro strip discontinuity after a section of delay line as reported in refs. The transponder is excited by a short pulse (1 ns) EM signal. The interrogation pulse is received by the transponder and reflected at various points along the micro strip line creating multiple echoes of the interrogation pulse. The time delay between the echoes is determined by the length of the delay line between the discontinuities. This type of tag is a replica of the SAW tag using micro strip technology, which makes it printable. Although initial trials and experiments of this chip-less technology have been reported, only 4 bits of data have been successfully encoded, which shows limited potential of this technology. 5.7 Chip-less RFID Transponders The Low Cost RFID Solution of the Future Spectral signature-based chip-less transponders encoded data into the spectrum using resonant structures. Each data bit is usually associated with the presence or absence of a resonant peak at a predetermined frequency in the spectrum. So far, five types of spectral signature-based tags have been reported and all five are considered to be fully printable. We can distinguish two types of spectral signature tags based on the nature of the tag: chemical tags and planar circuit tags. Chemical transponders are designed from a deposition of resonating fibers or special electronic ink. Two companies from Israel use nanometric materials to design chip-less tags. These tags consist of tiny particles of chemicals, which exhibit varying degrees of magnetism and when electromagnetic waves impinge on them they resonate with distinct frequencies, which are picked up -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 11 by the reader. They are very cheap and can easily be used inside banknotes and important documents for anti-counterfeiting and authentication. Cross ID, an Israeli paper company, claims to have such 70 distinct chemicals, which would thus provide unique identification in the order of 270 (over 1021) when resonated and detected suitably. Tape mark also claims to have “nanometric” resonant fibers, which are 5 mm in diameter and 1 mm in length. These tags are potentially low cost and can work on low grade paper and plastic package material. Unfortunately, they only operate at frequencies up to a few kHz, although this gives them very good tolerances to metal and water. Ink-tattoo chip-less tags use electronic ink patterns embedded into or printed onto the surface of the object being tagged. Developed by So mark Innovations, the electronic ink is deposited in a unique barcode pattern, which is different for every item. The system operates by interrogating the ink-tattoo tag by a high frequency microwave signal ( > 10 GHz) and is reflected by areas of the tattoo, which have ink creating a unique pattern which can be detected by the reader. The reading range is claimed to be up to 1.2 m (4 feet). In the case of animal ID, the ink is placed in a one-time-use disposable cartridge. For non-animal applications, the ink can be printed on plastic/paper or within the material. Based on the limited resources available for this technology (still in experimental phase), the author has assumed that it is spectral signature based. Planar circuit chip-less RFID transponders are designed using standard planar micro strip/co-planar waveguide/strip line resonant structure, such as antennas, filters and fractals. They are printed on thick, thin and flexible laminates and polymer substrates. Capacitively tuned dipoles were first reported by Jalaly. The chip-less tag consists of a number of dipole antennas, which resonate at different frequencies. When the tag is interrogated by a frequency sweep signal, the reader looks for magnitude dips in the spectrum as a result of the dipoles. Each dipole has a 1:1 correspondence to a data bit. Issues regarding this technology would be: tag size (lower frequency longer dipole—half wavelength) and mutual coupling effects between dipole elements. Space-filling curves used as spectral signature encoding RFID tags were first reported by McVay. The tags are designed as Peano and Hilbert curves with resonances centered around 900 MHz the tags represent a frequency selective 142 Low Cost Chip-less RFID Systems surface (FSS), which is manipulated with the use of space-filling curves (such as Hilbert curve, etc.). The transponder was successfully interrogated in an anechoic chamber. Only 3 bits of data have been reported so far. However, the tag requires significant layout modifications in order to encode data. LC resonant chip-less tag comprise a simple coil, which is resonant at a particular frequency. These transponders are considered 1-bit RFID transponders. The operating principle is based on the magnetic coupling between the reader antenna and the LC resonant tag. The reader constantly performs a frequency sweep searching for transponders. Whenever the swept -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 12 frequency corresponds to the transponder’s resonant frequency, the transponder will start to oscillate producing a voltage dip across the reader’s antenna ports. The advantage of these tags is their price and simple structure (single resonant coil), but they are very restricted in operating range, information storage (1 bit), operating bandwidth and multiple-tag collision. These transponders are mainly used for electronic article surveillance (EAS) in many supermarkets and retail stores. In the following section, the general RFID reader architecture and modern RFID reader review will be presented. 5.8 Chip-less RFID Reader The successful design and testing of the novel chip-less tag demands the development and design of a chip-less tag reader. Firstly, the design of a proof- of-concept chip-less tag reader which operates over 2–2.5 GHz only and reads a 6-bit tag is attempted. Two designs: first generation (Gen-1) reader, which decodes only the amplitude of the spectral signatures of the chip-less tag, and second generation (Gen-2) reader, which decodes both the amplitude and phase of the chip-less tag’s spectral signatures. Finally, a chip-less tag reader which operates over the UWB spectrum 5–10.7 GHz is presented. The UWB tag reader uses down-conversion blocks in the RF transceiver topology in order to process the received tag signal at an intermediate frequency (IF) band . Figure 5.10: Developed chip-less tag RFID readers. The three RFID readers, which are presented in this chapter and shown in Figure 5.10, differ mainly by the configurations of the RF transceivers and their frequency of operation. The transceiver topologies that are presented in this chapter are using two antennas and dedicated transmit and receive RF paths to RFID readers UWB (5 -10.7 GHZ) Narrowband (2- 2.5 GHZ) Gen -2 Reader Gen - 1 Reader -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 13 send interrogating CW signal to the tag and receive the encoded returned signals from the chip-less tag. Hence, the chip-less RFID system resembles bi- static radar, which uses two separately located TX and RX antennas. It is also the unique transceiver design for the chip-less tag readers that differ from conventional HF and UHF RFID readers that are found in the market today. The use of conventional readers is not possible, since the chip-less tag are unique by their nature of spectral signature-based data-encoding technique, while conventional tags use time-domain data-encoding techniques. This chapter is organized as follows: the operating principle of the proposed chip-less RFID tag compared to the conventional reader is presented. Next, the design and specifications of RF transceiver which determine the frequency band of operation, the modulation technique, the power requirement, etc. are presented. The design and development of the readers are presented followed by the result of the reader. The transceivers are tested by means of wired tag interrogation conditions (without antennas) in order to confirm their successful operations. 5.9 Differences Between Chipped and Chip-less Tag Readers The only commercially successful and fully operational chip-less RFID system is the SAW-based chip-less RFID designed by RFSAW©. A fully dedicated chip-less SAW tag reader was designed by the RFSAW engineers in order to accommodate the unconventional modulating and data-encoding properties of the SAW tag. Hence, it is imperative to design a reader that can read the multi resonator-based chip-less tag by decoding data from their spectral signatures. Although the use of conventional off-the-shelf RFID readers would be preferable, the new chip-less RFID tags demand a fully new development of the reader from scratch. Three main differences between the developed chip-less RFID tag reader and conventional off-the-shelf RFID reader are: conventional RFID readers operate mostly at HF (13.56 MHz), UHF (915 MHz) and microwave (2.45 GHz) bands, while the chip-less tag reader operates outside these bands; conventional readers use amplitude shift keying (ASK) and binary phase shift keying (BPSK) time-domain-based demodulation techniques, while the presented reader is decoding the tag by sweeping the microwave frequency spectrum and acquiring the tag’s spectral signature; and finally the proposed reader can process the tag data even after the tag has been read and left the interrogation zone, while conventional readers require the tag to be in the reader’s interrogation zone due to handshaking algorithms between tag and reader. The difference in frequency of operation between the chip-less tag reader and conventional RFID readers is more than obvious. As most chipped RFID systems operate in industrial, scientific and medical (ISM) bands, which have narrow bandwidths of a few KHz up to 83 MHz (2.45 GHz ISM band) due to feeless license options, the chip-less system proposed in this book operates in UWB region, which has a bandwidth greater than 500 MHz the most -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 14 commonly used data-encoding techniques for conventional RFID tags are ASK and PSK. Hence, RFID readers designed for detecting these tags also use these two modulation schemes for data encoding and decoding. This fundamentally means that conventional readers cannot detect and identify the chip-less tag with its spectral signatures and development of a dedicated chip-less RFID tag reader is necessary. The communication between conventional RFID tags and readers is usually performed by using a handshaking algorithm between the two. Another option is the use of tag polling by the reader, where each tag ID is stored in the reader’s data base. The reader transmits the tag ID’s from its database one at a time and awaits for the tag with the polled ID to respond. Both of these options require the tag to be in the interrogation zone of the reader. The reader’s interrogation zone is the area around the reader, where the tag can receive the reader’s signal and retransmit a signal back to the reader, which can be detected. In the case of a chip-less RFID system, the tag is fully passive and hence cannot respond to the reader’s polling, therefore no handshaking algorithms are possible or needed. Instead, the reader can perform processing of the tag’s signal even when the tag has left the interrogation zone of the reader due to this matter. The radio frequency transceiver is the heart of the proposed reader. The transmitter section generates the CW interrogation signal, and the receiver section received the echoes from the tag. Both sections are analogue circuits and set the link budget of the complete system. Therefore, it is vital to formulate the specifications, such as frequency of operation, transmit power level, interrogation signal type, receiver sensitivity, etc. In the following section, the specifications of the transceiver for the chip-less tag reader are presented. 5.10 Transceiver Specifications for Chip-less Tag Reader The initial step of the design procedures of the chip-less RFID tag reader is to formulate the specifications for a particular application. Hence, the specifications for the reader’s transceiver need to fit the reader specifications and carry extra parameters, such as power level of the interrogation signal, transmitter to receiver leakage/isolation and receiver sensitivity. One of the main governing parameters for formulating the specifications is bandwidth, design frequency and reading range. The bandwidth of the transceiver is defined as the frequency band over which the transceiver exhibits tolerable transmitter and receiver performances. The frequency of operation is set differently for different generations of readers. As for an example for the UWB reader, the transceiver is to operate within the UWB region (5–10.7 GHz). However, for Gen-1 and Gen-2, the transceivers are designed outside the UWB region for 2–2.5 GHz for less number of data bits and as the initial stage of the proof-of-concept exercise. The reading range of the RFID reader is determined by the reader’s transmitting power and the receiver’s sensitivity in order to ensure successful -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 15 tag interrogation and detection. Transmitting power limitations are dictated by standards, while the receiver’s sensitivity is limited by bandwidth and minimum signal power. Another important transceiver parameter which determines the transceiver architecture greatly is the type of interrogation that the reader is to perform. In this project, two specific options are explored: 1. Frequency sweep interrogation. 2. Pulse interrogation. Frequency sweep interrogation is defined as sweeping a CW signal over an operating frequency band in a specific time interval (similar to a spectrum analyzer). The advantages of this type of interrogation over pulsed interrogation are that the transmitter architecture is relatively simple to design and control [a voltage controlled oscillator (VCO) sweeps over a frequency band] and the receiver sensitivity is quite high. The disadvantages of this type of interrogation would be slower reading rates than those with a pulsed interrogation. Pulse interrogation is defined as the interrogation of the chip-less tag using a wideband pulse (or series of pulses) centered round the centre frequency of operation. The advantage of this type of interrogation is its high reading rates. The disadvantages are the need for ultra high speed switching components required for transmitter design, high speed ADC converters (above 1 GS/s) for receiver design and that the receiver detection is reduced due to sinc ( 𝐬𝐢𝐧 𝐱 𝐱 ) function frequency distribution. a- b- C- Quadrature d- Hybrid coupler Figure 5.11: Conventional RFID reader front end isolation architectures between TX and RX by using (a) Circulator, (b) Directional coupler, (c) Hybrid coupler and (d) Bi-static antennas. The isolation between the reader’s transmitter and receiver is also important since the RFID reader must operate in full duplex mode. A duplexer cannot be TX RX TX Direction coupler RX TX RX TX RX -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 16 used to remove the transmitter’s leakage signal since the tag will respond at the same frequency as the transmitted signal. Conventional RFID readers are designed with four transmitter isolation approaches to minimize the leakage. The typically used architectures utilize isolation components, such as Circulator (Figure 5.11 a), Directional coupler (Figure 5.11 b), Quadrature hybrid (Figure 5.11 c) and separate transmitter/receiver antenna, as shown in (Figure 5.11 d). The Circulator, Directional coupler and Quadrature hybrid architectures are significantly dependant on the performance of the three aforementioned components. The use of two antennas does not increase the isolation significantly unless the reader antennas are linearly cross-polarized. The chip-less tag reader transceiver designed in this project will have cross-polarized reader antennas for high TX/RX leakage cancelation. As mentioned earlier, the design of the transceiver is conducted by designing two proof-of-concept transceivers (Gen-1 and Gen-2) operating from 2 to 2.5 GHz, which are used to detect the 6-bit proof-of-concept chip-less tag. The third transceiver operates in the UWB region. 5.11 Gen-1 Transceiver The Gen-1 transceiver is designed to operate between 2 and 2.5 GHz and detect the amplitude variations of the tag’s spectral signature. In order to accomplish this, the receiver circuit utilizes a Schottky diode rectifier/detector circuit, which converts the RF signal to an equivalent DC output. The DC signal is then sent to the reader’s ADC for conversion to a digital signal. Figure 5.12: Block diagram of Gen-1 transceiver. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 17 Figure 5.13: Photograph of Gen-1 transceiver The block diagram and photograph of the Gen-1 transceiver are shown in Figures 5.12 and 5.13, respectively. The Gen-1 transceiver operates between 1.95 and 2.5 GHz and is consisted of a transmitter and receiver circuit. The RF components used for the design of the Gen-1 receiver are shown in Table 5.2. The control signals for the transmitter are sent from the DAC, which generates a tuning voltage for the VCO. The DAC generates a voltage ramp from 0 to 14 V in order to sweep the output signal frequency generated by the VCO from 1.95 to 2.5 GHz. The VCO is a Z-Communications V626ME10-LF. The output power of the VCO is approximately between 3 and 6 dBm, which is below the required 15 dBm, so a Mini-Circuit VNA-25 power amplifier is added as a gain block. Table 5.2: Gen-1 transceiver RF component specifications Component specifications V626ME10-LF VCO (Z-Communications) Output freq.: 1.9–2.55 GHz; Output power 3–6 dBm VNA-25 Power Amplifier (Mini-Circuits) Operating frequencies: 0.5–2.5 GHz; Gain = 10 dB LFCN-2500 Low Pass Filter (Mini-Circuits) Operating frequency: 0–2.5 GHz SMS7630-020 Schottky Diode (Skyworks) Operating frequencies: 0–10 GHz; Voltage drop: 0.11 V Cost Less than AU $85 In order to filter out any higher order/frequency products, a Mini-Circuits LFCN-2500 low pass filter (LPF) is used. The amplified and filtered signal is thus sent to the broadband reader antenna, which can be a UWB monopole antenna for short reading ranges and a LPDA for longer reading ranges. The -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 18 receiver circuit starts with an LFCN-2500 LPF, which is used to filter out any undesired frequencies above the 2.5 GHz band. The signal is further on amplified by two cascaded VNA-25 power amplifiers with low pass filtering stages in between. The signal is amplified in order to be an appropriate signal strength/power so that the diode-rectifying circuit may convert the RF power to DC. The diode rectifier consists of a shunt Skyworks Schottky diode and series 56 pf DC block and load capacitors and a 47 nH RF choke inductor. The circuit of the diode rectifier and Schottky diode model are made in ADS Analogue Schematic and are shown in Figure 5.14 a, b, respectively. The Schottky diode model is obtained from Skyworks Inc. The diode rectifier circuit acts as an RF envelope detector, which can be used to detect the dips in the RF power due to the chip-less tag stop band resonances. The Schottky diode model takes into account the capacitive and inductive properties of the SOT-143 packaging of the SMS7630-020 diode. The SOT-143 has four ports/ pins because there were two diodes in the SOT-143 packaging. In the following section, the design of the Gen-2 RFID reader transceiver is discussed. Figure 5.14: The circuit of the diode rectifier and Schottky diode model are made in ADS Analogue Schematic. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 19 5.12 Gen-2 Transceiver The Gen-2 transceiver is designed to operate between 2 and 2.5 GHz and detect both the amplitude and phase variation of the tag’s spectral signature. In order to accomplish this, the receiver circuit utilizes an AD8302 gain/phase detector circuit which generates a DC voltage output corresponding to the amplitude and phase difference between the reference RF signal and the received tag signal. The block diagram and photograph of the Gen-2 transceiver are shown in Figures 5.15 and 5.16, respectively. The RF components used for the design of the Gen-2 receiver are shown in Table 5.3. The transceiver consists of a transmitter and a receiver circuits. The transmitter circuit is controlled in the same way as the Gen-1 transceiver. The difference between the Gen-1 and Gen-2 transceiver is the power divider circuit, which provides a reference signal for the receiver circuit. The use of a single VCO means that the transceiver has a coherent architecture. The receiver circuit is the same as the Gen-1 except for the AD8302 gain/phase detector instead of the RF diode detector used in the Gen-1. The gain/phase detector is used to detect the variations in magnitude and phase of the received tag signal when compared to the reference signal supplied from the VCO. The AD8302 is multiplexed with a SN74LV4066A 8:1 multiplexer due to the use of a signal ADC on the digital control section of the RFID reader. The Gen-2 receiver is advanced in comparison to the Gen-1 receiver since it has both amplitude and phase spectral signature detection and decoding capabilities. Both amplitude and phase detection and decoding capabilities of the Gen-2 transceiver yield robust reading of the chip-less RFID tag. Figure 5.15: Block diagram of Gen-2 transceiver. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 20 Figure 5.16: Photograph of Gen-2 transceiver. This advantageous feature of the Gen-2 transceiver will be presented in the result section. With the design of the Gen-2 transceiver the proof-of-concept RFID transceiver circuit is complete. The next step in transceiver design for dedicated chip-less tag RFID reader is the design of a UWB transceiver, which has the capability to work above 2.5 GHz. Table 5.3: Gen-2 transceiver RF component specifications Component specifications V626ME10-LF VCO (Z-Communications) Output frequency: 1.9-2.55 GHz; Output power: 3-6 dBm VNA-25 Power Amplifier (Mini-Circuits) Operating frequency: 0.5-2.5 GHz; Gain = 10 dB LFCN-2500 Low Pass Filter (Mini-Circuits) Operating frequency: 0-2.5 GHz AD8302 Gain/Phase Detector Analog Devices Operating freq.: 0.3-2.7 GHz; Voltage output: 0-1.8 V SN74LV4066A 8-1 Multiplexer (Texas Instruments) Operating frequency: DC; Voltage output: 0-5 V 5.13 UWB Transceiver The UWB transceiver is designed to operate with 3.1 and 10.7 GHz and detect the amplitude and phase of the tag’s spectral signature. Therefore, it can be stated that the UWB transceiver circuit is an extension of the Gen-2 transceiver. The UWB receiver circuit utilizes the AD8302 gain/phase detector circuit, which generates a DC voltage output corresponding to the amplitude and phase differences between the two RF signals the reference from the transmitter and the received signal from the tag. The block diagram and photograph of the UWB transceiver are shown in figures 5.17 and 5.18. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 21 Figure 5.17: block diagram of UWB Transceiver. Figure 5.18: Photograph of UWB transceiver. As can be seen in figure 5.17, the UWB transceiver consists of a transmitter and receiver path. The transmitter consists of a powerful Teledyne YIG oscillator, which operates from 2 to 6 GHz and generates an interrogation signal of constant 15 dBm power to the TX antenna. Therefore, the power amplifiers are not needed in the transmitter path. The highest operating frequency of the UWB transceiver is limited by the highest operating frequency of the YIG oscillator, which can be extended by either upgrading the currently used oscillator or by adding a YIG oscillator working from 6 to 10.7 GHz. Table 5.4 shows the components used for the UWB transceiver design. From Figures 5.17 and 5.18, it is clear that the UWB transceiver utilizes a down -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 22 converting stage at the receiver, which consists of a pair of ZX05-14+ mixers. The UWB transceiver requires a pair of mixers since it has two IF channels fed into the AD8302 gain/phase detector unit: IF reference signal and IF tag signal. The IF signals cannot be above 2.7 GHz because the gain/phase detector can work only up to 2.7 GHz. The IF reference signal is obtained by down converting the RF signal separated from the YIG oscillator by a Narda 4014C- 10 10 dB coupler. The IF tag signal is obtained by down converting the received tag signal. The local oscillator (LO) is a Richardson RVC6000 VCO, which operates from 4 to 8 GHz. After the down-conversion stage, the IF tag signal is filtered and amplified since the free space loss attenuates the tag signal significantly. The IF amplifier circuits are Mimix broadband GMX7001 gain blocks, which give approximately 22 dB gain at 2 GHz each (cascaded over 40 dB gain). As discussed earlier, the gain/phase detector AD8302 provides a 0–1.8 V analogue DC voltage output at it is two output ports .The first port corresponds to the amplitude difference between the two IF signals, and the second port corresponds to the phase difference between the two IF signals. Table 5.4: UWB transceiver RF component specifications. Component specifications YIG Oscillator (Teledyne) Output frequency: 2–6 GHz; Output power: 15 dBm RVC6000 VCO (Richardson Electronics) Operating frequency: 4–8 GHz; Output power: 5 dBm 4014C-10 10 dB Coupler (Narda) Operating frequency: 3–10 GHz ZX05-14+ Mixer (Mini-Circuits) Operating frequency: 4–9 GHz; Attenuation: 24 dB LFCN-2500 Low Pass Filter (Mini-Circuits) Operating frequency: 0–2.5 GHz AD8302 Gain/Phase Detector Analog Devices Operating freq.: 0.3–2.7 GHz; Voltage output: 0–1.8 V Gain Blocks GMX7001 (Mimix Broadband) Operating frequency: 0–6 GHz; Gain: 22–14 dB Commercial Cost AU $3,800 Since only the tag’s IF signal changes depending on the tag’s spectral signature, the use of the reference signal decoupled from the transmitter path by a 10 dB coupler enables the detection of amplitude and phase variations in the tag’s spectral signature. The analogue DC outputs of the gain/phase detector are passed to the digital section for further processing. The UWB transceiver circuit is the ultimate design for interrogating the chip- less tag, receiving the tag’s response signal and processing it for decoding the spectral signature of the chip-less tag in both amplitude and phase. This is due to the fact that it has used most stable transmitter and highly sensitive receiver, which comprises expensive YIG oscillator, couplers, mixers, filters and the gain/phase detector. Therefore, it is expected that the most robust results are obtained from the UWB transceiver. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 23 5.14 Chip-less RFID Tag-Reader System Components The system specifications and conveyor belt application were presented in the preceding section. Two chip-less RFID systems with components are presented in this chapter. The first system is a 6-bit proof-of-concept chip-less RFID system, while the second RFID system is a UWB chip-less RFID system. The 6-bit proof-of-concept chip-less RFID system operates from 2 to 2.5 GHz. The system components of the proof-of-concept chip-less RFID system are shown in Figure 5.19. The proof-of-concept chip-less RFID system comprises a 6-bit chip-less RFID tag, which is detected either with a Gen-1 RFID reader (amplitude only spectral signature detection) or a Gen-2 RFID reader (with amplitude and phase spectral signature detection), and a Windows-based software application, which controls the RFID reader via an RS-232 bus and displays the received tag data. Figure 5.19: Block diagram of 6-bit proof-of-concept chip-less RFID system components. Figure 5.20: Block diagram of UWB chip-less RFID system components. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 24 The UWB chip-less RFID system operates from 5 to 10.7 GHz. The system components of the UWB chip-less RFID system are shown in Figure 5.20. The UWB chip-less RFID system comprises a 23-bit chip-less RFID tag, which is detected using an UWB RFID reader, and a Windows-based software application, which controls the RFID reader via RS-232 bus and displays the received tag data. The following sections present the chip-less tags, RFID readers and applications of the two chip-less RFID systems. 5.15 RFID Reader Digital Control Section The digital section is designed around an 8-bit Atmel AT89C52 microcontroller, which performs the major signal processing and data-decoding algorithms. The architecture of the digital section is presented in Figure 5.21. A microcomputer system has been used. The whole concept is based on using a CPU (AT89C52) and the peripheral components with specific external memory address allocations. The microcontroller communicates with the peripheral components via an 8-bit digital data bus and an 8-bit address bus. The data bus is connected to the 8-bit input ports of DAC, ADC and display buffers. The address bus is sent to the address decoder, which then determines which peripheral unit to activate. Each peripheral unit has a chip select (CS) pin, which activates the specific IC. After activating the peripheral unit, data is put on the data bus and the write signal is clocked, hence loading the IC with data from the CPU through the data bus. Figure 5.21: Block diagram of chip-less RFID reader digital control section. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 25 The photograph of the digital section is shown in Figure 5.22. The components used for the short range RFID reader are: • AT89S52 8-bit CMOS microcontroller—Atmel. • AD7533JN DAC—Analog Devices. • AD817AN High Speed Amplifier—Analog Devices. • AD7819 ADC—Analog Devices. • MAX232 RS232 Driver-Maxim-Dallas. • 6 Seven Segment Displays Common Anode. • Buffers and DFF Latches—Texas Instruments. The digital board was upgraded with a LCD display, keyboard and two 10-bit ADC instead of a single 8-bit ADC so that both amplitude and phase difference could be sampled simultaneously at a higher resolution. The upgraded digital section is used for the UWB RFID reader since it requires more frequency points and higher resolution due to its ultra-wide bandwidth operation. The following section presents the integrated RF transceiver and digital section for the Gen-1, Gen-2 and UWB RFID reader device. Figure 5.22: Photograph of RFID reader digital section. 5.16 Chip-less RFID Reader Tag Interrogation/Detec- tion Algorithm The Gen-1 and Gen-2 RFID readers interrogate the chip-less tag by sweeping the frequency spectrum (2–2.5 GHz) in 150–180 samples (amplitude data in 180 points and phase data in 150 points). The UWB RFID reader sweeps the 5- 10.7 GHz spectrum in 1,025 samples (5 MHz resolution). The -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 26 interrogation/detection algorithm implemented in all three RFID readers is presented in Figure 5.23. It was necessary to calibrate the RFID readers' first by setting up the experiment and then determining the necessary amplitude and phase data threshold, which determined logics “1” and “0”. This was done by interrogating a tag with all logic zeros in its ID and recording the data and then replacing the tag with all logic ones in its ID. Hence, a clear difference between what is logic “0” and what is logic “1” is created and recorded in the reader. The calibration procedure enables the detection of a tag in the reader’s interrogation area by measuring the received signal strength. Tag interrogation starts when the reader detects the received signal strength from a tag in its interrogation zone. After setting the interrogation frequency by loading the DAC with an 8-bit digital number corresponding to the necessary analog-tuning voltage for the VCO, the reader software reads data from the ADC. Figure 5.23: Flow chart of the RFID reader ID decoding algorithm. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 27 This data is the digitized values of the analog DC signals created by the gain/phase detector when comparing the received signal from the tag to the reference signal. The reader continues interrogating the tag until it reaches the final frequency sample. At this point, all the necessary data is collected and the tag ID decoding commences. The tag ID is decoded by using the threshold values established in the calibration routine. It is not necessary for the tag to be in the interrogation zone of the reader in order to perform this operation. After the tag ID has been decoded, it is sent to the display and/or via RS-232 to the host computer application. The algorithm returns to Tag Interrogation mode and waits to detect the presence of the next tag .This section finalizes the RFID reader hardware and software design. The following section presents the application software on a PC. 5.17 Application Software for Chip-less RFID System The application software is designed using Visual Basic 6 and operates on Windows XP operating system on a PC. The PC application software is used for automated data extraction from the reader. This means that there is no need for human interaction for the reader to interrogate the tag, send data to the PC application software using the RS-232 protocol where the tag ID and/or the tag data is presented. The application software starts by opening the port on the PC (COM2) and detects the RFID reader. If no RFID reader I detected, a warning is sent to the user. Once the reader is detected at the COM port, the application software sends an instruction to the reader for calibration. The calibration of the reader is performed by reading a tag with no resonances (all ones), which eliminates the influences of the environment. Once the reader is calibrated, the application software does not require any more calibration from the reader. The system is then set in tag detection mode. At any time, the user can choose to save the tag data received by the reader in an Excel spreadsheet. If this choice is made, a new Excel file opens for tag detection made by the reader and saves the data at a user-defined address on the PC. The reader operates in single as well as continuous tag interrogation. This is predetermined by the user by making this choice on the application software menu. A single read option will require a tag reading/detection to be defined by the user. Conclusion In this chapter, the differences between conventional and chip-less RFID readers, transceiver specifications, the design and testing of three transceiver topologies for the chip-less tag RFID readers are presented. The three transceiver topologies that were presented designed and tested were: Gen-1, Gen-2 and UWB transceivers. The Gen-1 transceiver was designed as a proof-of-concept detection circuit for the 6-bit tag on Taconic PCB substrate. The transceiver was designed to -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 28 operate between 2 and 2.5 GHz and detected the amplitude spectral signature data of the Electrical specifications Specifications Pre-design Tested Frequency of operation (GHz) 3.1–10.7 5–9 (due to component limitation) Transmitting power (dBm) 15 16 Interrogation signal type Frequency sweep Frequency sweep TX/RX isolation (dB) 60 Above 88 Receiver sensitivity (dBm) −35 −78 to −73 Max. Power consumption (Watts) 10 8.6 Commercial Cost Less than AU $2,000 (a guide only) $4,500 126 6 Transceiver Design for Chip-less RFID Tag Reader chip- less tag using a diode detector circuit at the receiver. The transceiver performed a linear frequency sweep interrogation technique to detect the resonant nulls of the tag. Successful detection of the tag’s spectral signature confirmed that the transceiver circuit was operational. Additional testing of the transmitter power output vs. frequency, receiver sensitivity and isolation between the transmitter and receiver were conducted and were within the pre-required limitations. The Gen-2 transceiver was the second designed transceiver, which was designed to detect the amplitude and phase spectral signature of the 6-bit tag on Taconic PCB substrate. The transceiver was designed to operate between 2 and 2.5 GHz and detected the amplitude and phase spectral signature data of the chip-less tag using a gain/phase detector AD8302. The Gen-2 transceiver architecture was based on coherent CW radar in order to neutralize any phase errors or frequency drifts coming from the transmitter’s VCO. The Gen-2 transceiver VCO performed a linear frequency sweep interrogation technique to detect the spectral signature of the tag. Successful detection of the tag’s amplitude and phase spectral signature confirmed that the transceiver circuit was operational. Additional testing of the transmitter power output vs. frequency, receiver sensitivity and isolation between the transmitter and receiver were conducted and were within the pre- required limitations. The third and final transceiver to be designed was the UWB transceiver. Since the chip-less RFID tags are designed to operate in the UWB region, a transceiver topology, which can perform frequency sweep interrogation within the UWB spectrum with amplitude and phase spectral signature detection, was designed. The UWB transceiver was designed to operate between 5 and 9 GHz due to limitations based on the components that were used (YIG oscillator and mixers). The UWB transceiver successfully detected the amplitude and phase spectral signature data of the chip-less tag using a gain/phase detector AD8302. The use of down-conversion mixers enabled the use of the AD8302 detector, which only operates up to 2.7 GHz. Hence, a RVC6000 VCO was used as a local oscillator to down convert the received tag signal. The transceiver architecture was based on coherent CW radar in order to neutralize any phase errors or frequency drifts coming from the transmitter’s YIG oscillator and LO VCO. The transceiver oscillator performed a linear frequency sweep interrogation technique to detect the spectral signature of the tag. Successful detection of the tag’s amplitude and -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Modern RFID Readers Chapter 5 ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | 5 - 29 phase spectral signature confirmed that the UWB transceiver circuit was operational. The use of phase data detection by a spectral signature detecting chip-less tag RFID reader was the first of its kind to be investigated, designed and tested. The use of phase decoding along with amplitude data decoding allows for comparison between the two for more robust and accurate readings. The following chapters will concentrate on the system integration of the chip- less tag and readers in order to complete the system performance evaluation. THE Chip-less RFID system utilizes two cross-polarized tag antennas and corresponding reader antennas in order to isolate the interrogation signal and the tag’s response signal. This requirement put stringent alignment and polarization prerequisites for the tag and the reader antennas. Since the RFID installed on a conveyor belt system is intended for single tag readings at a time, alignment and polarization requirements must be met for the system to operate properly. It is important to remember that the banknotes are intended to be tagged while still part of the banknote substrate which is the conveyor belt itself. Hence, every tag is printed correctly and exactly the same way on a different banknote, with correct polarization, same separation between tags and moving at a constant speed. The maximum reading range of the reader is limited by the reader’s sensitivity and emitted EM power. However, for the successful detection of the tag printed on the banknote (substrate) at a great reading range is not required. Hence, a nominal 10 cm reading range is nominated as the minimum reading range. The tag reading rate is a property of the RFID reader circuit. The reader needs to interrogate, detect and decode the tag’s identity before the next tag enters the reader’s interrogation zone. The highest read rate of the reader is determined by two factors: 1) Minimum signal bandwidth. 2) Digital circuit processing capabilities. The interrogation of the tag is performed using a linear frequency swept CW signal. The duration of the transmitted interrogation signal determines its bandwidth, i.e. a 1 m s CW signal has a bandwidth of 1 MHz Hence, and the desired spectral resolution determines length of the interrogation signal. For a 1 MHz resolution over a 5.7 GHz bandwidth, the interrogation time would be 5,700 × 1 m s = 5.7 ms. This means that 175 tags per second could be read with a resolution of 1 MHz This means that the reader would be operational for a conveyor belt moving at approximately 1 m/s (60 m/min). It is important to mention that a 1 MHz resolution could not be needed, which means that the interrogation time would decrease and hence the conveyor belt speed could increase if needed. Another important limiting factor is the electronics that are used for the reader supporting the interrogation speed. Most reduced instruction set computer (RISC) microprocessors can operate with an instruction cycle of 100 ns, while digital signal processors (DSP) operate with instruction cycles of up to 1 ns. Hence, we can conclude that the processing capabilities and speed of today’s microprocessors/DSP are sufficient to cater the interrogation of the banknotes on a conveyor belt. -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | D - 1 Simulation & Results -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | D - 2 Figure A.1.1: Folded Dipole Antenna. Figure A.1.2: Simulated return losses of the proposed antenna. 0.80 0.83 0.85 0.88 0.90 0.93 0.95 0.98 1.00 Freq [GHz] -12.50 -10.00 -7.50 -5.00 -2.50 0.00 dB(S(1,1)) HFSSDesign1XY Plot 1 ANSOFT Curve Info dB(S(1,1)) Setup1 : Sw eep -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | D - 3 Figure A.1.3: Impedance. Figure A.1.4: Measured gain of the proposed antenna. 0.80 0.83 0.85 0.88 0.90 0.93 0.95 0.98 1.00 Freq [GHz] -40.00 -20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 Y1 HFSSDesign1XY Plot 2 ANSOFT Curve Info im(Z(1,1)) Setup1 : Sweep re(Z(1,1)) Setup1 : Sweep 0.80 0.83 0.85 0.88 0.90 0.93 0.95 0.98 1.00 Freq [GHz] 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 dB(GainTotal) HFSSDesign1XY Plot 3 ANSOFT Curve Info dB(GainTotal) Setup1 : Sweep Phi='0deg' Theta='0deg' -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
    • Simulation & Results ‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬‫ـــــــ‬‫ــــــــــــــــــــــــــــــــــــــــــــــ‬ P a g e | D - 4 Figure A.2: Measured radiation patterns at 922MHz for the proposed antenna. 5.00 10.00 15.00 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern 1 ANSOFT 5.00 10.00 15.00 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern 2 ANSOFT 5.00 10.00 15.00 90 60 30 0 -30 -60 -90 -120 -150 -180 150 120 HFSSDesign1Radiation Pattern 3 ANSOFT -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment
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    • -MenoufiaUniversity[Combinedanduploadedbyamemberoftheteam(MohammedAli)] RadioFrequencyIdentificationByRFIDProjectTeam-FacultyofElectronicEngineering-Communicationdepartment