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7276575 sam-project

  1. 1. RESEARCH OF RFID & ANTENNAA report submitted in partial fulfillment of the requirement for the award of Bachelor of Engineering In Electronics & communication Engineering July, 2007 By Pawan sharma Under the guidance of Mr. Ravi Pratap Singh Kushwah Senior R&D Engineer Bar Code India Ltd. Gurgaon, India. Jagan Nath Gupta Institute of Engineering & Tecnology Plot No. IP-263, Sitapura Industrial Area, Phase-IV, Jaipur-302022
  2. 2. CERTIFICATE Certified that Pawan Sharma pursuing the course B.E (Electronics &Communication Engineering) from Jagan Nath Gupta Institute ofEngineering & Technology, jaipur, has completed her training under mysupervision in the Software Division of the R&D Department. At OmniaTecnology Pvt. Ltd, Gurgaon.The training has been carried out from 1th July ‘07 to 6th Augest ‘07.Ravi Pratap Singh KushwahSenior R&D EngineerOmnia Tecnology Pvt. Ltd.Gurgaon.
  3. 3. CANDIDATE’S DECLARATIONI hereby declare that the work that is presented in this dissertation,entitled Research of RFID & Antennain partial fulfillment of the requirements for the award of the degree of B.Techin Elec. & Comm. Engineering from the Jagan Nath Gupta Institute ofEngineering & Technology, jaipur, is an authentic record of work carried outduring the period July 2007 to Augest 2007 at Omnia Tecnology Pvt. Ltd.,Gurgaon.No part of this dissertation has been submitted to any other university orinstitution for any other degree or reward.Date: 25th May 2007 PAWAN SHARMAPlace: Gurgaon Instt. Roll No: A-38 Electronics&CommunicationEngineeing JNIT Institute of Engg. Jaipur.
  4. 4. ACKNOWLEDGEMENT The successful realization of the project is an outgrowth of aconsolidated effort of the people from disparate fronts. It’s only with theirsupport and guidance that the developer could meet the end. I am deeply indebted to my Project In charge Mr. Ravi ParatpSingh Kushwah, Senior R& D Engineer, for his invaluable technicalguidance and moral support provided during the course of my project.I am thankful to all my colleagues at Bar Code India Ltd for their fullcooperation and help during my stay there. Special thanks to Dr. Y.C. Bhat, Director JNIT Institute of Engg.Jaipur, Mr. Chaturvedi, HOD Elec.&Comm. Deptt. for providing me withan opportunity to take up this project and for their constant support andencouragement.Pawan sharmaJuly, 2007 TABLE OF CONTENTS
  5. 5. I. COMPANY PROFILE1.1 About Bar Code India Ltd.1.2 Services ProvidedII. PART-A (Study Phase)2.1 BARCODES 2.1.1 History 2.1.2 Symbologies2.2 Benefits of using Barcodes2.3 Replacing Barcodes-Evolution of RFID.2.4 Advantages of RFID vs. BarcodesIII. PART-B Radio Frequency Identification3.1 Overview3.2 RFID Frequencies 3.2.1 LF 3.2.2 HF 3.2.3 UHF 3.3.4 Microwave3.3 How RFID Technology works?3.4 RFID System3.5 Reader 3.5.1 Overview 3.5.2 Components 3.5.3Types 3.5.4 Serial Reader 3.5.5 Network Reader 3.5.6 Stationary Reader 3.5.7 Handheld Reader3.6 Tags 3.6.1 Passive Tags 3.6.2 Active Tags 3.6.3 Semi-Active Tags 3.6.4 Read-Only Tags 3.6.5 WORM 3.6.6 Read/Write 3.6.7 Non-RFID Tags3.7 Communication between Reader and Tags 3.7.1 Modulated backscattering 3.7.2 Transmitter Type 3.7.3 Transponder Type
  6. 6. 3.8 Reader Antenna 3.8.1 Antenna Polarization Linear Circular Patch 3.8.2 Antenna Power ERP EIRP3.9 Host and Software System 3.9.1 Edge Interface System Middleware Enterprise Backend Interface Enterprise backend Communication Infrastructure 3.9.2 Basic Concepts Tag Collision Reader Collision Tag Readability Tag Robustness 3.9.3 Characterization of RFID systems Based on Operating System Based on Read range Based on Physical Coupling System 3.9.4 EPC Standard Classification of RFID systems.3.10 Current UsesIV. PART-C Project Description- Technical Implementation of the System4.1 Serial Port Communication 4.1.1 Why Visual Basic? 4.1.2 Overview with example 4.1.3 Parameters 4.1.4 I/O Function in Visual Basic4.2 RS-2324.3 Some Programming Terminologies 4.3.1 Port Enabling 4.3.2 Receiving Data 4.3.3 Using Variables4.4 Some RFID Facts4.5 ConclusionV. REFERENCES
  7. 7. LIST OF TABLES1. RF Properties of Example Material Types.2. Properties of MSComm Control.3. MSComm Control Handshake Constants.4. OnComm Control.5. Error Constants.6. Input Mode Constants. LIST OF FIGURES1. Concept of RFID2. A schematic diagram of an RFID system3. A RFID System with example components.4. Simplified Block Diagram of a Reader5. Systematic diagram of a reader6. Symbol XR480 Reader7. Stationary Reader from Intermec Corporation8. IA39D Rugged Antenna9. Advanced ID Reader HH 80010. Components of Passive Tag11. Backscattering Communication12. Amplitude Modulated Backscattering Signal13. Transmitter Communication14. Simple Antenna Pattern15. An example antenna pattern containing protrusions16. Wave Pattern from a Linear polarized antenna.17. Wave Pattern from a Circular polarized antenna.18. A basic Patch Antenna.19. An RFID System from IT perspective.20. Inductive coupling21. Operating principle of a backscatter transponder22. Hand with the planned location of RFID chip.23. Hand after the operation to insert the RFID tag was completed.24. Character frame encoding25. RS 232 System26. Visual Basic Forms (1-10)
  8. 8. ABOUT BAR CODE INDIA LTDOmnia Technologies is a manufacturer of hi-quality RFID Tags and Labels. Our plant situated atIndustrial Modern Township (IMT), Gurgaon, India has all the modern state of the art manufacturingfacility for manufacturing RFID products.Omnia has the capabilities to manufacture the RFID tags and labels in various frequency ranges like125 KHz, 13.56 MHz, 868 MHz. etc.Our Research and Development Department with analysts and designers, comprises of state-of-the-art test equipment & analyzers with a focus to develop high quality, innovative and industry relevantdesigns at competitive prices.The Environmental Test Lab consists of all the required testing equipments that ensure products arevalidated at regular interval.Current product range (Different frequencies – LF, HF and UHF): Tags Key Fobs Mount on Metal Wrist Bands Customized Tags.Software Services Apart from hardware components, the main component of any AIDC solutionis the software which enables the hardware components to deliver the desired results.
  9. 9. Bar Code India Ltd develops these enabling software components in order to achievethe AIDC solution objective. With in-house skilled team of software developers andsolution designers, the turnkey solutions are provided. In order to achieve theseobjectives, industry standard software development procedures are followed.Barcode ScannersBarcode PrintersMobile ComputersWirelessRFIDConsumablesManufacturingLogisticsRetailIn-The–FieldHealthcareBar coding
  10. 10. Mobile ComputingWireless LANRFIDField ApplicationSystem IntegrationLabel PrintingPART-A
  11. 11. 2.1 BARCODES2.1.1 History The first barcode was developed in 1948 by two graduate students at DrexelInstitute of Technology, Bernard Silver and Norman Joseph Woodland. They filed for aU.S. patent in October 1949 and it was granted in 1952. Its implementation was madepossible through the work of Raymond Alexander and Frank Stietz, two engineers withSylvania, as a result of their work on a system to identify railroad cars (who were alsogranted a patent). It was not until 1966 that barcodes were put to commercial use andthey were not commercially successful until the 1980s. While traditionally barcode encoding schemes represented only numbers, newersymbologies add new characters such as the uppercase alphabet to the complete ASCIIcharacter set and beyond. The drive to encode more information in combination with thespace requirements of simple barcodes led to the development of matrix codes (a type of2D barcode), which do not consist of bars but rather a grid of square cells. Stackedbarcodes are a compromise between true 2D barcodes and linear codes, and are formedby taking a traditional linear symbology and placing it in an envelope that allowsmultiple rows.2.1.2 Symbologies The mapping between messages and barcodes is called a symbology. Thespecification of a symbology includes the encoding of the single digits/characters of themessage as well as the start and stop markers into bars and space, the size of the quietzone required to be before and after the barcode as well as the computation of achecksum.Linear symbologies can be classified mainly by two properties:• Continuous vs. discrete: Characters in continuous symbologies usually abut, with one character ending with a space and the next beginning with a bar, or vice versa. Characters in discrete symbologies begin and end with bars; the inter character space is ignored, as long as it is not wide enough to look like the code ends.• Two-width vs. many-width: Bars and spaces in two-width symbologies are wide or narrow; how wide a wide bar is exactly has no significance as long as the symbology requirements for wide bars are adhered to (usually two to three times more wide than a narrow bar). Bars and spaces in many-width symbologies are all multiples of a basic width called the module; most such codes use four widths of 1, 2, 3 and 4 modules. Some symbologies use interleaving. The first character is encoded using blackbars of varying width. The second character is then encoded, by varying the width of thewhite spaces between these bars. Thus characters are encoded in pairs over the samesection of the barcode. Interleaved 2 of 5 is an example of this.
  12. 12. Stacked symbologies consist of a given linear symbology repeated vertically in multiple. There are a large variety of 2-D symbologies. The most common are matrixcodes, which feature square or dot-shaped modules arranged on a grid pattern. 2-Dsymbologies also come in a variety of other visual formats. Aside from circular patterns,there are several 2-D symbologies which employ steganography by hiding an array ofdifferent-sized or -shaped modules within a user-specified image (for example, DataGlyph).2.2 BENEFITS OF USING BARCODES In point-of-sale management, the use of barcodes can provide very detailed up-to-date information on key aspects of the business, enabling decisions to be made muchmore quickly and with more confidence. For example:• Fast-selling items can be identified quickly and automatically reordered to meet consumer demand,• Slow-selling items can be identified, preventing a build-up of unwanted stock,• The effects of repositioning a given product within a store can be monitored, allowing fast-moving more profitable items to occupy the best space,• Historical data can be used to predict seasonal fluctuations very accurately.• Besides sales and inventory tracking, barcodes are very useful in shipping/receiving/tracking.• When a manufacturer packs a box with any given item, a Unique Identifying Number (UID) can be assigned to the box.• A relational database can be created to relate the UID to relevant information about the box; such as order number, items packed, qty packed, final destination, etc...• The information can be transmitted through a communication system such as Electronic Data Interchange (EDI) so the retailer has the information about a shipment before it arrives.• Tracking results when shipments are sent to a Distribution Center (DC) before being forwarded to the final destination.• When the shipment gets to the final destination, the UID gets scanned, and the store knows where the order came from, whats inside the box, and how much to pay the manufacturer. The reason bar codes are business friendly is that bar code scanners are relativelylow costing and extremely accurate – only about 1/100,000 entries will be wrong.2.3 REPLACING BARCODES—EVOLUTION OF RFID RFID tags are often envisioned as a replacement for UPC or EAN barcodes,having a number of important advantages over the older barcode technology. They may
  13. 13. not ever completely replace barcodes, due in part to their higher cost and in other part tothe advantage of more than one independent data source on the same object. The newEPC, along with several other schemes, is widely available at reasonable cost. The storage of data associated with tracking items will require many terabytes onall levels. Filtering and categorizing RFID data is needed in order to create usefulinformation. It is likely that goods will be tracked preferably by the pallet using RFIDtags or at package level with Universal Product Code (UPC) or EAN from uniquebarcodes. The unique identity in any case is a mandatory requirement for RFID tags,despite special choice of the numbering scheme. RFID tag data capacity is big enoughthat any tag will have a unique code, while current bar codes are limited to a single typecode for all instances of a particular product. The uniqueness of RFID tags means that aproduct may be individually tracked as it moves from location to location, finally endingup in the consumers hands. This may help companies to combat theft and other formsof product loss. Moreover, the tracing back of products is an important feature that getswell supported with RFID tags containing not just a unique identity of the tag but alsothe serial number of the object. This may help companies to cope with qualitydeficiencies and resulting recall campaigns, but also contributes to concern over post-sale tracking and profiling of consumers.2.4 ADVANTAGES OF RFID VERSUS BARCODES RFID tags and barcodes both carry information about products. However, thereare important differences between these two technologies:• Barcode readers require a direct line of sight to the printed barcode; RFID readers do not require a direct line of sight to either active RFID tags or passive RFID tags.• RFID tags can be read at much greater distances; an RFID reader can pull information from a tag at distances up to 300 feet. The range to read a barcode is much less, typically no more than fifteen feet.• RFID readers can interrogate, or read, RFID tags much faster; read rates of forty or more tags per second are possible. Reading barcodes is much more time-consuming; due to the fact that a direct line of sight is required, if the items are not properly oriented to the reader it may take seconds to read an individual tag. Barcode readers usually take a half-second or more to successfully complete a read.• Line of sight requirements also limit the ruggedness of barcodes as well as the reusability of barcodes. (Since line of sight is required for barcodes, the printed barcode must be exposed on the outside of the product, where it is subject to greater wear and tear.) RFID tags are typically more rugged, since the electronic components are better protected in a plastic cover. RFID tags can also be implanted within the product itself, guaranteeing greater ruggedness and reusability.• Barcodes have no read/write capability; that is, you cannot add to the information written on a printed barcode. RFID tags, however, can be read/write devices; the
  14. 14. RFID reader can communicate with the tag, and alter as much of the information as the tag design will allow.• RFID tags are typically more expensive than barcodes.• Human intervention is required to scan a barcode, whereas in most applications an RFID tag can be detected "hands off."• Barcodes must be visible on the outside of product packaging. RFID tags can be placed inside the packaging or even in the product itself.• The readability of barcodes can be impaired by dirt, moisture, abrasion, or packaging contours. RFID tags are not affected by those conditions.• More data can be stored in an RFID tag than can be stored on a barcode.• RFID has portable databases.• Multiple tags can be Read/Write at the same time.II. PART –B
  15. 15. RADIO FREQUENCY IDENTIFICATION1. Overview Radio Frequency Identification (RFID) is one member in the family of AutomaticIdentification and Data Capture (AIDC) technologies and is a fast and reliable means ofidentifying just about any material object automatically. Primarily, the two main components involved in a Radio Frequency Identificationsystem are the Transponder (tags that are attached to the object) and the Interrogator(RFID reader). Communication between the RFID reader and tags occurs wirelessly andgenerally does not require a line of sight between the devices. Radio-frequency identification (RFID) is an automatic identification method, relyingon storing and remotely retrieving data using devices called RFID tags or transponders.An RFID tag is an object that can be attached to or incorporated into a product, animal,or person for the purpose of identification using radio waves. All RFID tags contain atleast two parts. One is an integrated circuit for storing and processing information,modulating and demodulating a radio frequency (RF) signal and perhaps otherspecialized functions. The second is an antenna for receiving and transmitting the signal. The RFID tag can automatically be read from several meters away and does not haveto be in the line of sight of the reader. The current thrust in RFID use in supply chainmanagement for large enterprises. RFID increases the speed and accuracy with whichinventory can be tracked and managed thereby saving money for the business. RFID technology uses radio waves to automatically identify physical objects (eitherliving beings or inanimate items). Therefore, the range of objects identifiable using RFIDincludes virtually everything on this planet (and beyond).
  16. 16. 3.2 RFID Frequency Radio waves are the carriers of data between the reader and transponders. Theapproach generally adopted for RFID communication is to allocate frequenciesdepending on application. The frequencies used cover a wide spectrum. These specified bands are:• Low frequency (LF)• High frequency (HF)• Ultra high frequency (UHF)• Microwave frequencyThe following subsections discuss these frequency types.3.2.1 Low Frequency (LF) Frequencies between 30 KHz and 300 KHz are considered low, and RFIDsystems commonly use the 125 KHz to 134 KHz frequency range. A typical LF RFIDsystem operates at 125 KHz or 134.2 KHz. RFID systems operating at LF generally usepassive tags, have low data-transfer rates from the tag to the reader, and are especiallygood if the operating environment contains metals, liquids, dirt, snow, or mud (a veryimportant 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 largestinstalled base. The LF range is accepted worldwide.
  17. 17. 3.2.2 High Frequency (HF) HF ranges from 3 MHz to 30 MHz, with 13.56 MHz being the typical frequencyused 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 ofmetals and liquids. HF systems are also widely used, especially in hospitals (where itdoes not interfere with the existing equipment). The HF frequency range is acceptedworldwide. The next frequency range is called very high frequency (VHF) and lies between 30and 300 MHz. Unfortunately, none of the current RFID systems operate in this range.Therefore, this frequency type is not discussed any further.3.2.3 Ultra High Frequency (UHF) UHF ranges from 300 MHz to 1 GHz. A typical passive UHF RFID systemoperates at 865-867 MHz in India. RFID system operates at 315 MHz and 433 MHz. AUHF system can therefore use both active and passive tags and has a fast data-transferrate between the tag and the reader, but performs poorly in the presence of metals andliquids (not true, however, in the cases of low UHF frequencies such as 315 MHz and 433MHz). UHF RFID systems have started being deployed widely because of the recentRFID mandates of several large private and public enterprises. The UHF range is notaccepted worldwide.3.2.4 Microwave Frequency Microwave frequency ranges upward from 1 GHz. A typical microwave RFIDsystem 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 thetag 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 apassive tag operating in the microwave range has the smallest length (which results in asmall tag size because the tag microchip can also be made very small). The 2.4 GHzfrequency range is called Industry, Scientific, and Medical (ISM) band and is acceptedworldwide. International restrictions apply to the frequencies that RFID can use. Therefore,some of the previously discussed frequencies might not be valid 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
  18. 18. difference exists between the two points on the material, the atoms between these two points can become charged and conduct electric current.Table 1: RF Properties of Example Material TypesMaterial LF HF UHF MicrowaveClothing RF-lucent RF-lucent RF-lucent RF-lucentDry wood RF-lucent RF-lucent RF-lucent RF-absorbentGraphite RF-lucent RF-lucent RF-opaque RF-opaqueLiquids RF-lucent RF-lucent RF-absorbent RF-absorbent(some types)Metals RF-lucent RF-lucent RF-opaque RF-opaqueMotor oil RF-lucent RF-lucent RF-lucent RF-lucentPaper RF-lucent RF-lucent RF-lucent RF-lucentproductsPlastics RF-lucent RF-lucent RF-lucent RF-lucent (some types)Shampoo RF-lucent RF-lucent RF-absorbent RF-absorbentWater RF-lucent RF-lucent RF-absorbent RF-absorbentWet wood RF-lucent RF-lucent RF-absorbent RF-absorbent3.3 How RFID technology works? A radio device called a tag is attached to the object that needs to be identified.Unique identification data about this tagged object is stored on this tag. When such atagged object is presented in front of a suitable RFID reader, the tag transmits this datato the reader (via the reader antenna). The reader then reads the data and has thecapability to forward it over suitable communication channels, such as a network or aserial connection, to a software application running on a computer. This application canthen use this unique data to identify the object presented to the reader. It can thenperform a variety of actions such as updating the location information of this object inthe database, sending an alert to the floor personnel, or completely ignoring it (if aduplicate read, for example). As you can understand from this description, RFID is also a data-collectiontechnology. However, this technology has some unique characteristics that enable usersto apply it in areas beyond the reach of traditional data-collection technologies, such asbar codes.
  19. 19. An RFID application is implemented by an RFID system, which constitutes theentire technology end-to-end.3.4 RFID System An RFID system is an integrated collection of components that implement anRFID solution. An RFID system consists of the following components (in singular form) from anend-to-end perspective:• Tag. This is a mandatory component of any RFID system.• Reader. This is a mandatory component, too.• Reader antenna. This is another mandatory component. Some current readers available today have built-in antennas.• Controller. This is a mandatory component. However, most of the new- generation readers have this component built in to them.• Sensor, actuator and annunciator. These optional components are needed for external input and output of the system.• Host and software system. Theoretically, an RFID system can function independently without this component. Practically, an RFID system is close to worthless without this component.• Communication infrastructure. This mandatory component is a collection of both wired and wireless network and serial connection infrastructure needed to connect the previously listed components together to effectively communicate with each other.Figure 2: A schematic diagram of an RFID system.
  20. 20. The basic system consists of central reader with its controller. The reader has an antennafor communication to take place through it. The reader has a communication interface tointeract with the tag which has to be identified. The reader has a software system as itsbackend. The tag is placed in the vicinity of the antenna.Figure 3: An RFID system with example components. These figures may seem "reader-centric" because the RFID reader seems to be atthe center of the entire system. Therefore, this figure might seem to be slanted, forexample, toward the RFID vendor viewpoint. 1. Trigger event detected by sensors.
  21. 21. 2. Reader is turned on. 3. Reader reads a tag. 4. Tag data is sent to the software system by the reader. 5. Software system instructs the reader to turn on the annunciator. 6. Annunciator is turned on. 7. Trigger is sent to reader.3.5 READER3.5.1 Overview An RFID reader is a device that is used to interrogate an RFID tag. The readerhas an antenna that emits radio waves; the tag responds by sending back its data. An RFID reader typically contains a module (transmitter and receiver), a controlunit and a coupling element (antenna). The reader has three main functions: energizing,demodulating and decoding. In addition, readers can be fitted with an additionalinterface that converts the radio waves returned from the RFID tag into a form that canthen be passed on to another system, like a computer or any programmable logiccontroller. Anti-Collision algorithms permit the simultaneous reading of large numbersof tagged objects, while ensuring that each tag is read only once. An RFID reader, also called an interrogator, can read from and write data tocompatible RFID tags. Thus, a reader also doubles up as a writer. The act of writing thetag data by a reader is called creating a tag. The process of creating a tag and uniquelyassociating it with an object is called commissioning the tag. Similarly, decommissioninga tag means to disassociate the tag from a tagged object and optionally destroy it. Thetime during which a reader can emit RF energy to read tags is called the duty cycle ofthe reader. International legal limits apply to reader duty cycles. The reader is the central nervous system of the entire RFID hardware system—establishing communication with and control of this component is the most importanttask of any entity which seeks integration with this hardware entity. A number of factors can affect the distance at which a tag can be read (the readrange). The frequency used for identification, the antenna gain, the orientation andpolarization of the reader antenna and the transponder antenna, as well as theplacement of the tag on the object to be identified will all have an impact on the RFIDsystem’s read range.A reader has the following main components:• Transmitter• Receiver
  22. 22. • Microprocessor • Memory • Input/output channels for external sensors, actuators, and annunciators (Although, strictly speaking, these are optional components, they are almost always provided with a commercial reader.) • Controller (which may reside as an external component) • Communication interface • Power Figure 4: Simplified Block Diagram of a RFID ReaderOscillator Modulator Amplifier To/ Fro m Antenn RFI a D Tag Demodulat Filter/or Amplifier Decoder Display To Video Module Display
  23. 23. Figure 5: The components of an example reader.The following subsections describe these components.Transmitter The reader’s transmitter is used to transmit AC power and the clock cycle via itsantennas to the tags in its read zone. This is a part of the transceiver unit, the componentresponsible for sending the reader’s signal to the surrounding environment andreceiving tag responses back via the reader antenna(s). The antenna ports of a reader areconnected to its transceiver component. One reader antenna can be attached to each suchantenna port. Currently, some readers can support up to four antenna ports.Receiver This component is also part of the transceiver module. It receives analog signalsfrom the tag via the reader antenna. It then sends these signals to the readermicroprocessor, where it is converted to its equivalent digital form (that is, the digitalrepresentation of the data that the tag has transmitted to the reader antenna).Microprocessor This component is responsible for implementing the reader protocol tocommunicate with compatible tags. It is performs decoding and error checking of theanalog signal from the receiver. In addition, the microprocessor might contain customlogic for doing low-level filtering and processing of read tag data.Memory Memory is used for storing data such as the reader configuration parameters anda list of tag reads. Therefore, if the connection between the reader and the
  24. 24. controller/software system goes down, not all read tag data will be lost. Depending onthe memory size, however, a limit applies as to how many such tag reads can be storedat any one time. If the connection remains down for an extended period with the readerreading tags during this downtime, this limit might be exceeded and part of the storeddata lost (that is, overwritten by the other tags that are read later).Input/Output Channels for External Sensors, Actuators, and Annunciators Readers do not have to be turned on for reading tags at all times. After all, thetags might appear only at certain times in the read zone, and leaving readers perpetuallyon would just waste the reader’s energy. In addition, as mentioned previously,regulatory limits apply to the reader duty cycle, too. This component provides amechanism for turning a reader on and off depending on external events. A sensor ofsome sort, such as a motion or light sensor, detects the presence of tagged objects in thereader’s read zone. This sensor can then set the reader on to read this tag. Similarly, thiscomponent also allows the reader to provide local output depending on some conditionvia an annunciator (for example, sounding an audible alarm) or an actuator (forexample, opening or closing a security gate, moving a robot arm, and so forth). Sensors,actuators, and annunciators are discussed later in this chapter.Controller A controller is an entity that allows an external entity, either a human or acomputer program, to communicate with and control a reader’s functions and to controlannunciators and actuators associated with this reader. Often, manufacturers integratethis component into the reader itself (as firmware, for example). However, it is alsopossible to package this as a separate hardware/software component that must bebought together with the reader. Controllers are discussed in detail later in this chapter.Communication Interface The communication interface component provides the communicationinstructions to a reader that allow it to interact with external entities, via a controller, totransfer its stored data and to accept commands and send back the correspondingresponses. You can assume that this interface component is either part of the controlleror is the medium that lies between a controller and the external entities. This entity hasimportant characteristics that make it necessary to treat this as an independentcomponent. A reader could have a serial as well as a network interface forcommunication. A serial interface is probably the most widespread type of readerinterface available, but next-generation readers are being developed with networkinterfaces as a standard feature. Sophisticated readers offer features such as automaticdiscovery by an application, embedded Web servers that allow the reader to acceptcommands and display the results using a standard Web browser, and so forth.
  25. 25. Power This component supplies power to the reader components. The power source isgenerally provided to this component through a power cord connected to anappropriate external electrical outlet.3.5.3 TYPES OF READERS Like tags, readers can also be classified using two different criteria. The firstcriterion is the interface that a reader provides for communication. Based on this,readers can be classified as follows:• Serial• NetworkThe following subsections describe these reader types.3.5.4 Serial Reader Serial readers use a serial communication link to communicate with anapplication. The reader is physically connected to a computer’s serial port using an RS-232 or RS-485 serial connection. Both of these connections have an upper limit on thecable length that can be used to connect a reader to a computer. RS-485 allows a longercable length than RS-232 does. The advantage of serial readers is that the communication link is reliablecompared to network readers. Therefore, the use of these readers is recommended tominimize dependency on a communication channel.3.5.5 Network Reader Network readers can be connected to a computer using both wired and wirelessnetworks. In effect, the reader behaves like a network device installation that does notrequire any specialized knowledge of the hardware. Note, however, that SNMP-typemonitoring features are currently available for just a few network reader types.Therefore, the majority of these readers cannot be monitored as standard networkdevices.The next classification of reader type can be made based on its mobility, as follows:• Stationary• HandheldThe following subsections describe these reader types.
  26. 26. 3.5.6 Stationary Reader A stationary reader, also called a fixed reader, is what its name implies. Thesereaders are mounted on a wall, portal, or some suitable structure in the read zone. Thestructure on which the reader is mounted may not be static! For example, somestationary readers are mounted on forklifts. Similarly, you can mount these readersinside delivery trucks. In contrast to tags, readers are not generally very tolerant of harshenvironmental conditions. Therefore, if you install a reader outdoors or on movingobjects, take care to ruggedize it properly. Stationary readers generally need externalantennas for reading tags. A reader can provide up to four external antennas ports.Figure 6: Symbol XR480 Reader The XR480 reader builds on Symbol’s commercially proven XR400 RFID readerplatform and supports the European ETSI 302-208 standard reliable read performancefor today’s industrial-scale RFID implementations. The XR480 also delivers Generation 2(Gen 2) dense-reader mode operation which enables flexibility. The XR480 is the only commercially available EPC-compliant RFID readerapproved for use in Europe to provide support for up to eight read points which helpsdecrease deployment complexity and increases flexibility. The Symbol XR480 is also thefirst commercially available EPC-compliant RFID reader. XR480 RFID reader enablesseamless integration and interoperability with existing IT infrastructure while reducingthe support costs associated with multi-platform environmentsFigure 7: IF4 Stationary Reader from Intermec Corporation
  27. 27. • An intelligent peripheral – capable of internal filtering to reduce network traffic. • Software configurable to read/write EPC Class 1, EPC Gen 2 and ISO tags. • Factory configurable to operate in 865MHz, 869MHz, 915MHz or 950MHz RFID bands. • Directly monitors and controls presence detectors and signal lights.Figure 8: IA39D Rugged Antenna • Rigid matching network and circuit boards • Stainless steel mounting hardware. • The IA39D is specifically designed for operation in the 865 – 928 MHz frequency band.A stationary reader can generally operate in the following modes:• Autonomous• InteractiveThe following subsections describe these modes.Autonomous Mode In autonomous mode, a reader continuously read tags in its read zone. Everytime a tag is read, it is saved to a list, usually called a tag list. An item on the tag list isassociated with what is generally called persist time. If the associated tag cannot be readfor a period of time exceeding it’s persist time, it is dropped from the tag list. Anapplication running on a host machine can register itself to receive the tag listperiodically. A tag list includes information such as the following:• Unique tag identifiers• Reading time• How many times a particular tag has been read since it has been discovered (that is, first read by the reader)
  28. 28. • The antenna ID that read a particular tag• Reader nameInteractive Mode In interactive mode, a read receives and executes commands from an applicationrunning on a host machine or from a user using a vendor-supplied client tocommunicate with the reader. After the reader fully executes the current command, itwaits for the next. A reader can execute a range of commands, from sending the currenttag list to the command invoker to changing the reader’s configuration parameters.3.5.7 Handheld ReaderFigure 9: Advanced ID Reader HH 800WORK INSTRUCTION FOR ADVANCED ID READER (1) WAKE UP Push the power switch and hold it for a moment. (2) OWNER ID Reader is now waiting for the User to enter the owner ID. (a) Inputting owner ID by reading (scanning) an RFID tag.
  29. 29. Once the unit reads a tag which is present in front of the antenna, it will ‘beep’ and then display Action screen. (b) Inputting owner ID by using the keyboard. Owner ID is keyed into the reader manually and then ‘OK’ is pressed to confirm. The unit will then ‘beep’. (3) ACTION Users have to select action for the reading. Users can define each action by using 16 buttons on the keyboard. Press ‘OK’ to confirm the action. (4) TAG COUNT (a) Display current Tag Count and wait for user to continue. (b) Display current Tag Count and wait for user to reset or continue. (5) DATA DISPLAY To read RFID tags in Read Mode, point the antenna module at tags- (a) Reader will read the tags. (b) Display unique tag ID of each tag read. (c) Count continually as long as switch is pressed. (d) LCD will display the action selected. (e) If lot of tags present, it will display the last tag read. A handheld reader is a mobile reader that a user can operate as a handheld unit.A handheld reader generally has built-in antenna(s). Although these readers aretypically the most expensive (and few are commercially available), recent advances inreader technology are resulting in sophisticated handheld readers at lower prices. At Barcode India Ltd, the most frequently used reader is Advanced ID Reader asshown in figure above.3.6 TAGS An RFID tag is a device that can store and transmit data to a reader in a contactless manner using radio waves.RFID tags can be classified in two different ways. The following list shows the firstclassification, which is based on whether the tag contains an on-board power supplyand/or provides support for specialized tasks:• Passive• Active• Semi-active (also known as semi-passive)
  30. 30. The following subsections discuss these in detail. (The other classification isdiscussed after this.)3.6.1 Passive Tags This type of RFID tag does not have an on-board power source (for example, abattery), and instead uses the power emitted from the reader to energize itself andtransmit its stored data to the reader. A passive tag is simple in its construction and hasno moving parts. As a result, such a tag has a long life and is generally resistant to harshenvironmental conditions. For example, some passive tags can withstand corrosivechemicals such as acid, temperatures of 400ºF (204ºC approximately), and more. In tag-to-reader communication for this type of tag, a reader alwayscommunicates first, followed by the tag. The presence of a reader is mandatory for sucha tag to transmit its data. A passive tag is typically smaller than an active or semi-active tag. It has avariety of read ranges starting with less than 1 inch to about 30 feet (9 metersapproximately).A passive tag is also generally cheaper compared to an active or semi-active tag. A contact less smart card is a special type of passive RFID tag that is widely usedtoday 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 notneed to be physically in contact with the reader for reading.A passive tag consists of the following main components:• Microchip• Antenna The organization of these components is as shown in the figure below.
  31. 31. Figure 10: Components of a passive tag.. • The power control/rectifier converts AC power from the reader antenna signal to DC power. • It supplies power to the other components of the microchip. • The clock extractor extracts the clock signal from reader antenna signal. • The modulator modulates the received reader signal. • The tag’s response is embedded in the modulated signal, which is then transmitted back to the reader. • The logic unit is responsible for implementing the communication protocol between the tag and the reader. • The microchip memory is used for storing data. This memory is generally segmented (that is, consists of several blocks or fields). Addressability means the ability to address (that is, read or write) the individual memory of a tag’s microchip. A tag memory block can hold different data types, such as a portion of the tagged object identifier data, checksum (for example, cyclic redundancy checks [CRC]) bits for checking the accuracy of the transmitted data, and so on. Recent advances in technology have shrunk the size of the microchip to less than the size of a grain of sand. However, a tag’s physical dimensions are not determined by the size of its microchip but by the length of its antenna.3.6.2 Active Tags Active RFID tags have an on-board power source (for example, a battery; othersources of power, such as solar, are also possible) and electronics for performingspecialized tasks. An active tag uses its on-board power supply to transmit its data to a
  32. 32. reader. It does not need the reader’s emitted power for data transmission. The on-boardelectronics can contain microprocessors, sensors, and input/output ports powered bythe on-board power source.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.3.6.3 Semi-Active (Semi-Passive) Tags Semi-active tags have an on-board power source (for example, a battery) andelectronics for performing specialized tasks. The on-board power supply providesenergy to the tag for its operation. However, for transmitting its data, a semi-active taguses the reader’s emitted power. A semi-active tag is also called a battery-assisted tag. The reading distance of a semi-active tag can be 100 feet (30.5 metersapproximately) under ideal conditions using a modulated backscatter scheme (in UHFand microwave).The next classification, as shown here, is based on the capability to support datarewrites:• Read-only (RO)• Write once, read many (WORM)• Read-write (RW)Both active and passive tags can be RO, WORM, and RW. The following sections discussthese classifications in detail.3.6.4 Read Only (RO) An RO tag can be programmed (that is, written) just once in its lifetime. The datacan be burned into the tag at the factory during the manufacturing stage. To accomplishthis, 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 lifetimeof the tag. Such a tag is also called factory programmed. The tag manufacturer suppliesthe data on the tag, and the tag users typically do not have any control over it. This typeof tag is good for small applications only, but is impractical for large manufacturing orwhen tag data needs to be customized based on the application. This tag type is usedtoday in small pilots and business applications.
  33. 33. 3.6.5 Write Once, Read Many (WORM) A WORM tag can be programmed or written once, which is generally done notby the manufacturer but by the tag user right at the time when the tag needs to becreated. In practice, however, because of buggy implementation, it is possible tooverwrite particular types of WORM tag data several times (about 100 times is notuncommon)! 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 datasecurity, and is the most prevalent type of tag used in business today.3.6.6 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 thereaders or by the tag itself (in case of active tags). An RW tag typically contains a Flashor a FRAM memory device to store its data. An RW tag is also called fieldprogrammable 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’sapplications, a fact that might change in the future as the tag technology andapplicability increases with a decrease in tag cost. It is important to briefly pause here and describe a type of RFID tag called surfaceacoustic wave (SAW) before moving on to the next topic.3.6.7 Non-RFID Tags The concept of attaching a tag and having it wirelessly transmit its unique ID to areader is not the exclusive domain of RF waves. You can use other types of wirelesscommunications for this purpose. For example, you can use ultrasonic and infraredwaves for tag-to-reader communication. Ultrasonic communication has the additional advantages that it does not causeinterference with existing electrical equipment and cannot penetrate through walls. As aresult, ultrasonic tagging systems can be deployed in hospitals, where such technologycan coexist with the existing medical equipment. In addition, an ultrasonic reader and atag must be within the same room for the tag to be read by the reader. This requiredproximity can prove helpful in asset monitoring and tracking. An infrared tag uses light to transmit its data to a reader. Because light cannotpenetrate through walls, an infrared tag and reader must both be in the same room for
  34. 34. communication. If an obstacle covers the light source of a tag, the tag can no longercommunicate with a reader (a serious disadvantage).3.7 Communication between a Reader and a Tag Depending on the tag type, the communication between a reader and a tag canbe one of the following:• Modulated backscatter• Transmitter type• Transponder type Before delving into the details of these communication types, it is important foryou to understand the concepts of near field and far field. The area between a reader antenna and one full wavelength of the RF waveemitted by the antenna is called near field. The area beyond one full wavelength of the RFwave emitted from a reader antenna is called far field. Passive RFID systems operating inLF and HF use near field communication, whereas those in UHF and microwavefrequencies use far field communication. The signal strength in near fieldcommunication attenuates as the cube of the distance from the reader antenna. In farfield, it attenuates as square of the distance from the reader antenna. As a result, far fieldcommunication is associated with a longer read range compared with near fieldcommunication.Next, a comparison between tag read and tag write is in order. Tag write takes a longer time than tag read under the same conditions because awrite operation consists of multiple additional steps, including an initial verification,erasing any existing tag data, writing the new tag data, and a final verification phase. Inaddition, the data is written on the tag in blocks in multiple steps. As a result, a singletag write can take hundreds of milliseconds to complete and increases with the increasein data size. In contrast, several tags can be read in this time interval by the same reader.Also, tag write is a sensitive process that needs the target tag to be closer (compared toits corresponding read distance) to the reader antenna for the entire write operation.This closer proximity ensures the tag antenna can derive sufficient energy from thereader antenna signal to power its microchip so that it can execute the write instructions.The power requirement for write operation is generally significantly higher than thatrequired for reading. The write operation might fail otherwise. However, a tag does nothave to stay close to the reader during a read operation. Also, during tag writeoperation, any tag other than the target should not be in write range of the reader.Otherwise, in some cases, this other tag might accidentally get written rather than the
  35. 35. target tag. This write range issue is clearly not relevant during a read operation, whenmultiple tags can exist in the read range of the reader at the same time.3.7.1 Modulated Backscattering Modulated backscatter communication applies to passive as well as to semi-active tags. In this type of communication, the reader sends out a continuous wave (CW)RF signal containing AC power and clock signal to the tag at the carrier frequency (thefrequency at which the reader operates). Through physical coupling (that is, amechanism by which the transfer of energy takes place from the reader to the tag), thetag antenna supplies power to the microchip. The word excite is frequently used toindicate a passive tag microchip drawing power from a reader’s signal to properlyenergize itself. About 1.2 volts are generally necessary to energize the tag microchip forreading purposes. For writing, the microchip usually needs to draw about 2.2 volts fromthe reader signal. The microchip now modulates or breaks up the input signal into asequence of on and off patterns that represents its data and transmits it back. When thereader receives this modulated signal, it decodes the pattern and obtains the tag data. Thus, in modulated backscatter communication, the reader always "talks" first,followed by the tag. A tag using this scheme cannot communicate at all in the absence ofa reader because it depends totally on the reader’s power to transmit its data. A related term, beam power, is also used in this context, and means that a tag isusing the reader’s power to modulate the reader signal back. Note that a passive tagexclusively uses beam power to transmit its data. A semi-active tag uses beam power toclock its oscillator and generate the transmit signal back. Thus, in essence, a semi-activetag also uses beam power to transmit its data.
  36. 36. Figure 11: Backscatter communication. This is the communication method used by a passive RFID tag to send data backto the reader. By repeatedly shunting the tag coil through a transistor, the tag can causeslight fluctuations in the reader’s RF carrier amplitude. The RF link behaves essentiallyas a transformer; as the secondary winding (tag coil) is momentarily shunted, theprimary winding (reader coil) experiences a momentary voltage drop. The reader mustpeak-detect this data at about 60 dB down (about 100 mV riding on a 100V sine wave) asshown in Figure 1. This amplitude-modulation loading of the reader’s transmitted fieldprovides a communication path back to the reader. The data bits can then be encoded orfurther modulated in a number of ways.Figure 12: Amplitude Modulated Backscattering Signal3.7.2 Transmitter Type This type of communication applies to active tags only. In this type ofcommunication, the tag broadcasts its message to the environment in regular intervals,
  37. 37. irrespective of the presence or absence of a reader. Therefore, in this type ofcommunication, the tag always "talks" first rather than the reader.Figure 13: Transmitter communication.3.7.3 Transponder Type This type of communication applies to a special type of active tags calledtransponders (as discussed previously). In this type of communication, the tag goes to a"sleep" or into a dormant stage in the absence of interrogation from a reader. In thisstate, the tag might periodically send a message to check whether any reader is listeningto it. When a reader receives such a query message, it can instruct the tag to "wake up"or end the dormant state. When the tag receives this command from the reader, it exitsits current state and starts to act as a transmitter tag again. (That is, it starts broadcastingits message periodically to its surroundings.) In this type of communication, the tag datais sent only when the reader specifically asks for it.3.8 Reader Antenna A reader communicates to a tag through the reader’s antennas, a separate devicethat is physically attached to a reader, at one of its antenna ports, by means of a cable.This cable length is generally limited to between 6 and 25 feet. (However, this lengthlimit may vary.) As mentioned previously, a single reader can support up to fourantennas (that is, have four physical antenna ports). A reader antenna is also called thereader’s coupling element because it creates an electromagnetic field to couple with the tag.An antenna broadcasts the reader transmitter’s RF signal into its surroundings andreceives tag responses on the reader’s behalf. Therefore, proper positioning of theantennas, not the readers, is essential for good read accuracy (although a reader has to belocated somewhat close to an antenna because of the limitation of the antenna cablelength). In addition, some stationary readers might have in-built antennas. As a result, inthis case, positioning the antennas for a reader is equivalent to positioning the readeritself. In general, RFID reader antennas are shaped like rectangular or square boxes.
  38. 38. Figure 14: Simple antenna pattern. In reality, because of antenna characteristics, the footprint of an antenna is neveruniformly shaped like an ellipsoid but almost always contains deformities orprotrusions. Each protrusion is surrounded by dead zones. Such dead zones are alsocalled nulls. The reflection of reader antenna signals on RF-opaque objects causes what isknown as multipath. In this case, the reflected RF waves are scattered and can arrive atthe reader antenna at different times using different paths. Some of the arriving wavescould be in phase (that is, exactly match with the original antenna signal’s wave pattern).In this case, the original antenna signal is enhanced when these waves impose with theoriginal waves giving rise to protrusions. This phenomenon is also known asconstructive interference. Some of the waves could also arrive out of phase (that is, theexact opposite of the original antenna wave pattern). In this case, the original antennasignal is cancelled when these two wave types impose on each other. This is also calleddestructive interference. Nulls are created as a result.
  39. 39. Figure 15: An example antenna pattern containing protrusions. A tag placed in one of the protruded regions will read, but if this tag movesslightly so that it is inside the surrounding dead region, the tag cannot be read (whichmight lead to no intuitive tag-reading behavior). For example, when placed a certaindistance away from a reader, a tag does not read, but when moved slightly in onedirection, it can be read by the reader; if this tag is then moved slightly in anotherdirection, however, it cannot be read! The read behavior of a tag near a protruded regionis thus unreliable. Therefore, when you place an antenna to cover a read area, it isimportant that you not depend on these protruded regions to maximize the readdistance. The best strategy is to stay inside the main ellipsoid-shaped region even if itmeans sacrificing the read range by a few feet—better safe than sorry. It is extremely important to determine the antenna footprint; the antennafootprint determines where a tag can or cannot be read. The manufacturer mightprovide the antenna footprint as part of the antenna’s specifications. However, youshould use such information as a guideline only, because the actual footprint will mostlikely vary depending on the operating environment. You can use well-definedtechniques such as signal analysis to map an antenna footprint. In signal analysis, thesignal from the tag is measured, using equipment such as a spectrum analyzer and/or anetwork analyzer, under various conditions (for example, in free space, different tagorientations, and on conductive materials or absorptive materials). By analyzing thesesignal strengths, you can precisely determine the antenna footprint. Antenna polarization, another important concept of reader antenna design, isdiscussed in the following section.3.8.1 Antenna Polarization
  40. 40. As discussed previously, an antenna emits electromagnetic waves into itssurroundings. The direction of oscillation of these electromagnetic waves is called thepolarization of the antenna. What does this mean to tag readability? A great deal! Thereadability of a tag, together with its reading distance and reading robustness, greatlydepends on the antenna polarization and the angle at which the tag is presented to thereader.The main antenna types in UHF, based on polarization, are• Linear polarized• Circular polarized3.8.1.1 Linear Polarized Antenna In this antenna type, the RF waves emanate in a linear patter from the antenna.These waves have only one energy field.Figure 16: Wave pattern from a linear polarized antenna. A linear polarized antenna has a narrower radiation beam with a longer readrange compared to a circular polarized antenna. In addition, a narrower radiation beamhelps a linear polarized antenna to read tags within a longer, narrow but well-definedread region (compared to a circular polarized antenna), instead of reading tagsrandomly from its surroundings. However, a linear polarized antenna is sensitive to tagorientation with respect to its polarization direction. These types of antenna aretherefore useful in applications where the tag orientation is fixed and predictable. Circular Polarized Antenna RF waves radiate from a circular polarized antenna in a circular pattern. Thesewaves have two constituting energy fields that are equal in amplitude and magnitude,
  41. 41. but have a phase difference of 90º. Therefore, when a wave of an energy field is at itshighest value, the wave of the other field is at its lowest.Figure 17: Wave pattern from a circular polarized antenna. Because of the nature of polarization, a circular polarized antenna is largelyunaffected by tag orientation. Therefore, this type of antenna proves ideal forapplications where the tag orientation is unpredictable. A circular polarized antenna hasa wider radiation beam and hence reads tags in a wider area compared to a linearpolarized antenna. This antenna is preferred for an RFID system that uses high UHF ormicrowave frequencies in an operating environment where there is a high degree of RFreflectance (due to presence of metals and so forth).Often, a patch antenna is used for making UHF antennas, as described in the followingsubsection. Patch Antenna A patch antenna, also called a microstrip or planar antenna, in its basic formconsists of a rectangular metal foil or a plate mounted on a substrate such as Teflon. Theother side of the substrate is coated with a metallic substance. A microstrip connected tothe rectangular metal foil supplies power to the antenna. The power supply type can bevaried to make a patch antenna circular or linear polarized.
  42. 42. Figure 18: A basic patch antenna.3.8.3 Antenna Power An antenna emits power measured in either effective radiated power (ERP) units inEurope or in equivalent isotropic radiated power (EIRP) units in the United States. ERP andEIRP are not the same but are related by the relation EIRP = 1.64 ERP. Effective radiated power (e.r.p.) (in a given direction): The power supplied to an antenna multiplied by the antenna gain in a givendirection. If the direction is not specified, the direction of maximum gain is assumed.The type of reference antenna must be specified. The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction. If the direction is not specified, the direction ofmaximum gain is assumed. The effective radiated power of a transmitter (with antenna, transmission line,duplexers, etc.,) is the power that would be necessary at the input terminals of areference half-wave dipole antenna in order to produce the same maximum field
  43. 43. intensity. ERP is usually calculated by multiplying the measured transmitter outputpower by the specified antenna system gain, relative to a half-wave dipole, in thedirection of interest. Effective isotropic ally radiated power (e.i.r.p.): Effective Isotropic Radiated Power (EIRP), also known as Equivalent Isotropically Radiated Power, is the amount of power that would have to be emitted by anisotropic antenna (that evenly distributes power in all directions and is a theoreticalconstruct) to produce the peak power density observed in the direction of maximumantenna gain. EIRP can take into account the losses in transmission line and connectorsand includes the gain of the antenna. The EIRP is often stated in terms of decibels over areference power level that would be the power emitted by an isotropic radiator withequivalent signal strength. The EIRP allows making comparisons between differentemitters regardless of type, size or form. From the EIRP, and with knowledge of a realantennas gain, it is possible to calculate real power and field strength values.The arithmetic product of (a) the power supplied to an antenna and (b) its gain. The maximum possible value of antenna power is limited by national andinternational (for example, FCC in the United States) regulations. To use an antennawith higher power than the allowable limit, you must obtain explicit permission fromthe appropriate regulatory body. You can always reduce antenna power, however, byplacing a small device called an attenuator in the transmission line (for example, betweenan antenna connector and the reader port). As a result, the antenna’s signal strength isreduced, and the antenna’s read range is diminished. Attenuation proves very useful insituations where the read zone needs to be constrained as a part of system requirementsso that tags are only read inside but not outside this region. The ability of an attenuatorto reduce the antenna strength varies depending on the attenuator.Controller A controller is an intermediary agent that allows an external entity tocommunicate with and control a reader’s behavior together with the annunciators andactuators associated with this reader. A controller is the only component of an RFIDsystem (or a reader, depending on point of view) through which reader communicationsare possible; no other medium or entity provides this ability. As mentioned previously, acontroller for a reader can be embedded inside the reader or can be a separatecomponent by itself. An analogy is in order. A controller to a reader is what a printerdriver is for a computer printer. To print a document from a computer to a printer, thecomputer must have the appropriate printer driver software installed. Similarly, toretrieve tag data stored on a reader, a computer must use a controller—it cannotcommunicate to the reader in any other way.
  44. 44. A controller also provides (or uses, depending on viewpoint) a communicationinterface for the external entities to interact with it (as described previously in the sectionabout readers).3.9 HOST AND SOFTWARE SYSTEM Figure 19: An RFID System from IT perspective The reader (together with the tag and antenna) is located at the edge of thesystem. This figure might be interpreted as how an RFID system looks from an IT orsystem-integrator perspective. An RFID system thus has two parts—the first part (edge) governed by laws ofphysics and the second part involving information technology (IT). Both parts are veryimportant. A state-of-the-art IT system is worthless if the data from its physicalcounterpart is unreliable and patchy. Similarly, a finely tuned RFID hardware setup isuseless if the associated IT system cannot intelligently manage and process the datagenerated by this system. Detailed discussion of these components will be done in latersections. An RFID system supports bidirectional communication flows, from the readersto the back end and from the back end to the readers. The host and software system is an all-encompassing term for the hardware andsoftware component that is separate from the RFID hardware (that is, reader, tag, andantenna); the system is composed of the following four main components:
  45. 45. • Edge interface/system• Middleware• Enterprise back-end interface• Enterprise back end In a nontrivial RFID system, all these components are present to some degree.The following sections discuss these components.3.9.1 Edge Interface/System This component integrates the entire host and software system with the RFIDhardware (which consists of the reader, tag, and antenna). This integration isaccomplished by establishing communication with and control of the central nervoussystem of RFID hardware: the readers. Therefore, this component’s main task is to getdata from the readers, control the readers’ behavior and use the readers to activate theassociated external actuators and annunciators. This component is logically and physically closest to the RFID hardware and canbe considered to be at the edge when viewed from the host and software systemperspective. Therefore, this is also the right place for this component to activate externalactuators and annunciators without any need to go through the reader. This placementproves very useful because then the choice and control capabilities of annunciators andactuators are not limited by the reader support, but can be extended as and whenneeded by customizing the edge system. The edge system is also the perfect place to hide the nitty-gritty details ofinteraction with a specific reader (through its controller) from a particular manufacturer.Therefore, this component also provides an abstraction layer for any type of readersneeded by the RFID system. This abstraction layer is very desirable because then the restof the host and software system can use this abstraction to interact with any supportedreaders, present and future, without any need to change itself. This component can be viewed as a kind of a super controller that can be used tointeract with any supported reader controller in the RFID system. Moreover, this component can do several other tasks that are beyond theresponsibilities of a simple controller, such as the following:• Filter out duplicate reads from different readers• Allow setting of event-based triggers that can automatically activate an annunciator or an actuator• Provide intelligent functions such as aggregating and selectively sending out tag data to host and software system• Remote reader management• Remote management of itself
  46. 46. As apparent from the preceding discussion, this component may actually behosted on specialized hardware as an embedded system. The rest of the host andsoftware system can then interact with this embedded system over a wired or a wirelessnetwork. This component can be implemented using a standard such as Open ServicesGateway initiative (OSGi), which defines a standard for dynamic delivery of softwareservices to network devices (see Chapter 10). In a very simple case of a trivial, possiblythrowaway, pilot, this component might be completely absent. Middleware The middleware component can be broadly defined as everything that liesbetween the edge interface and the enterprise back-end interface. This component can beviewed as the central nervous system of the RFID system from the software perspective(RFID readers can be considered the same from an RFID hardware perspective) in that itprovides core functionality of the system, including the following:• Data sharing both inside and outside of an enterprise• Efficient management of massive data produced by RFID system• Provide generic components that can be used as building blocks for implementing the business specific filtering and aggregation logic• Open standard based so that it is compatible with a wide range of other software systems• Enable loose coupling between the edge interface and the enterprise back-end interface (and thus any change in the former will minimally affect the latter)In the extreme case of a trivial, possibly throwaway, pilot, this component might becompletely absent. This is the most complex and important component of the host and softwaresystem. As a result, a principle part of the implementation effort will be spent onimplementing this component. Therefore, when implementing an RFID system, it isalways preferable to procure this component as an off-the-shelf system from RFIDsoftware and services vendors. You can then customize it to meet the applicationrequirements. Enterprise Back-End Interface The enterprise back-end interface component is used to integrate the middlewarecomponent with the enterprise back-end component. This is the place for implementingbusiness process integration. Which processes need to be integrated with the RFIDsystem will determine the amount of effort needed to implement this component. Thiseffort can be substantial if business process changes are involved or comprehensive.Because the middleware is a generic component, some customization is almost alwaysneeded to trigger transactions and transfer data between it and the enterprise back end.It is not uncommon to find enterprise-scale integration interfaces natively built in to the
  47. 47. enterprise scale systems, such as ERP and WMS that are available from large third-partysoftware vendors. Enterprise Back End The enterprise back-end component encompasses the complete suite ofapplications and IT systems of an enterprise. This is thus the data repository and thebusiness processes engine for the entire enterprise. In an RFID system context, thiscomponent provides the directory data for the tagged objects to the middlewarecomponent. Note that in general, integration with a handful of applications or systems isnecessary to achieve a satisfactory integration with the enterprise back end and hencethe business processes. This is, of course, assuming that this component is wellarchitected and implemented. This component generally involves minimum effort from the implementationperspective of an RFID system because this is already built and functional. However, insome cases (for example, proprietary system elements), some effort might be necessaryto actually modify or enhance this component to make it compatible with the RFIDsystem that is being built. Communication Infrastructure This component provides connectivity and enables security and systemsmanagement functionalities for different components of an RFID system, and istherefore an integral part of the system. It includes the wired and wireless network, andserial connections between readers, controllers, and computers. The wireless networktype can range from a personal area network (PAN, provided by Bluetooth), to a local areanetwork (LAN, offered by 802.11x technology), to a wide area network (WAN, provided by2.5G/3G technologies). Satellite communication networks, for example, usinggeosynchronous L-band satellites are also becoming an increasing reality for RFIDsystems that need to work in a very wide geographical area where existence of apervasive reader infrastructure is not guaranteed.It is now time to pause for a moment and learn about the basic concepts of an RFIDsystem.3.9.2 Basic Concepts This section discusses the following terms that are frequently used in reference toan RFID system:• Frequency• Tag collision• Reader collision
  48. 48. • Tag readability• Read robustness Frequency is the most important attribute of an RFID system. It has already beendiscussed in detail in the beginning of this chapter.The remaining terms are discussed in detail now in the following subsections. Tag Collision Contrary to popular belief, a reader can only communicate with one tag at atime. When more than one tag attempts to communicate with the reader at the sametime, 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. Areader then needs to communicate with the conflicting tags using what is called asingulation 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 aremost widely used:• ALOHA for HF• Tree Walking for UHF Using one of these anti-collision algorithms, a reader can identify several tags inits read zone in a very short period of time. Thus, it appears that this reader iscommunicating with these tags almost simultaneously. Reader Collision When the read zone (or read window) of two or more readers overlap, the signalfrom one reader can interfere with the signal from another. This phenomenon is calledreader collision. This situation can arise if the antennas of these two readers are installedin such a manner that it gives rise to destructive interference (antenna footprint). As aresult, RF energy from one of the antennas of a reader "cancels out" the RF energy fromone of the antennas of the other reader. To avoid this problem, position the readerantennas so that the antenna of one reader does not directly face the antenna of anotherreader. If the direct facing of these antennas is unavoidable, separate them a sufficientdistance so that their read zones do not overlap. You can use proper attenuators toattune the antenna power to achieve this. In addition, two antennas of the same readercan generally overlap without creating a reader collision, because the power to theantennas is physically transferred by the reader in such a manner that only one antennais active at a time. As a result, there is no chance of two or more antennas of this readeremitting signals at the same time. You can also use another technique, called timedivision multiple access (TDMA), to avoid reader collision. In this scheme, the readers areinstructed to read at different times rather than all reading at the same time. As a result,the antenna of only one reader is active at a time. The problem with this approach is thata tag can be read more than one time by different readers in the overlapping read zone.
  49. 49. Therefore, some intelligent filtering mechanism must be implemented by the controlleror the edge system/interface to filter out the duplicate tag reads. Tag Readability Tag readability of an RFID system for a particular operating environment can bedefined as the capability of the system to read a specific tag data successfully. Tagreadability depends on a number of factors (see Chapter 9, "Designing andImplementing an RFID Solution"). From a simple perspective, an RFID system needs toread a tag successfully just once to provide good tag readability. To make this guarantee,however, the system should be designed so that it can read a single tag several times, sothat even if a tag read fails several times there’s a good chance that one of the reads willsucceed. In other words, an RFID system should have good read for robustness. This isthe topic of the next section. Read Robustness Read robustness (also called read redundancy) is the number of times a particulartag 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 oftime spent by the tag in the read zone decreases with an increase in its speed. Thisresults in a decrease of read robustness for this tag. The number of tags present at onetime in the read zone also can hamper read robustness because the number of tags thatcan be read by a reader per unit time is limited.3.9.3 Characterization of an RFID System An RFID system can be characterized in three different ways using the followingattributes:• Operating frequency• Read range• Physical coupling methodThese criteria are interrelated. The first two criteria are most frequently used in practice.All three characterizations are discussed next. Characterization Based on Operating Frequency Operating frequency is the most important attribute of an RFID system. It is thefrequency at which the reader transmits its signal. It is closely associated with the typicalreading distance attribute. In most cases, the frequency of an RFID system is determinedby its typical reading distance requirement. Frequency has already been describedearlier in this chapter.
  50. 50. Characterization Based on Read Range Read range of an RFID system is defined as the reading distance between the tagand the reader. Using this criterion, an RFID system can be divided into the followingthree types:• Close coupled• Remote coupled• Long rangeThe following subsections describe these types.Close-Coupled System The read range of the RFID systems belonging to this class is less than 1 cm. TheLF and HF RFID systems belong to this category.Remote-Coupled System The RFID systems belonging to this class have a read range of 1 cm to 100 cm.Again, this category contains LF and HF RFID systems.Long-Range System RFID systems having a read range of more than 100 cm belong to this class. RFIDsystems operating in the UHF and microwave frequency range belong to this group. Characterization Based on Physical Coupling Method Physical coupling refers to the method used for coupling the tag and the antenna(that is, the mechanism by which energy is transferred to the tag from the antenna).Based on this criterion, three different types of RFID systems are possible:• Magnetic• Electric• ElectromagneticThese following subsections discuss these different types.Magnetic-Coupled System These types of RFID systems are also known as inductive-coupled systems orinductive-radio systems. Inductive Coupling is the transfer of energy from one circuit toanother through a shared magnetic field. An electrical current passing through the coilof a primary conductor creates a magnetic field that induces an electrical current in thecoil of a secondary conductor exposed to the magnetic field.
  51. 51. Low Frequency (LF) and High Frequency (HF) passive RFID devices useinductive coupling to transfer energy from the interrogators antenna to the tag. The taguses the transferred energy to power circuitry that modulates the impedance of the tagantenna, thereby sending a data stream back through the magnetic field to theinterrogator The LF and HF RFID systems belong to this category. An inductively coupled transponder comprises of an electronic data carryingdevice, usually a single microchip and a large area coil that functions as an antenna. Inductively coupled transponders are almost always operated passively. Thismeans that all the energy needed for the operation of the microchip has to be providedby the reader. For this purpose, the readers antenna coil generates a strong, highfrequency electro-magnetic field, which penetrates the cross-section of the coil area andthe area around the coil. Because the wavelength of the frequency range used (< 135kHz: 2400 m, 13.56 MHz: 22.1 m) is several times greater than the distance between thereaders antenna and the transponder, the electro-magnetic field may be treated as asimple magnetic alternating field with regard to the distance between transponder andantenna. A small part of the emitted field penetrates the antenna coil of the transponder,which is some distance away from the coil of the reader. By induction, a voltage Ui isgenerated in the transponders antenna coil. This voltage is rectified and serves as thepower supply for the data carrying device (microchip). A capacitor C1 is connected inparallel with the readers antenna coil, the capacitance of which is selected such that itcombines with the coil inductance of the antenna coil to form a parallel resonant circuit,with a resonant frequency that corresponds with the transmission frequency of thereader. Very high currents are generated in the antenna coil of the reader by resonancestep-up in the parallel resonant circuit, which can be used to generate the required fieldstrengths for the operation of the remote transponder. The antenna coil of the transponder and the capacitor C1 to form a resonantcircuit tuned to the transmission frequency of the reader. The voltage U at thetransponder coil reaches a maximum due to resonance step-up in the parallel resonantcircuit.
  52. 52. Figure 20: Inductive CouplingElectric-Coupled System These types of RFID systems are also known as capacitive-coupled systems. The LFand HF RFID systems belong to this category. With capacitive coupling, the antenna’s resistance is no longer a critical factor, soantennas can be constructed from materials of considerably higher resistance than themetals used in inductive technology. In particular, this means that conductive inks,which have a moderate resistance, can be used to form the antenna.Electromagnetic-Coupled System The majority of RFID systems belonging to this class are also called backscattersystems. RFID systems operating in the UHF and microwave frequency range belong tothis group. Electromagnetic waves are reflected by objects with dimensions greater thanaround half the wavelength of the wave. The efficiency with which an object reflectselectromagnetic waves is described by its reflection cross-section. Objects that are inresonance with the wave front that hits them, as is the case for antenna at theappropriate frequency for example, have a particularly large reflection cross-section.
  53. 53. Figure 21: Operation principle of a backscatter transponder Power P1 is emitted from the readers antenna, a small proportion of which (freespace attenuation) reaches the transponders antenna. The power P1 is supplied to theantenna connections as HF voltage and after rectification by the diodes D1 and D2 thiscan be used as turn on voltage for the deactivation or activation of the power saving"power-down" mode. The diodes used here are low barrier Schottky diodes, which have aparticularly low threshold voltage. The voltage obtained may also be sufficient to serveas a power supply for short ranges. A proportion of the incoming power P1 is reflected by the antenna and returnedas power P2. The reflection characteristics (= reflection cross-section) of the antenna can beinfluenced by altering the load connected to the antenna. In order to transmit data fromthe transponder to the reader, a load resistor RL connected in parallel with the antennais switched on and off in time with the data stream to be transmitted. The amplitude ofthe power P2 reflected from the transponder can thus be modulated (à modulatedbackscatter). The power P2 reflected from the transponder is radiated into free space. A smallproportion of this (free space attenuation) is picked up by the readers antenna. Thereflected signal therefore travels into the antenna connection of the reader in the"backwards direction" and can be decoupled using a directional coupler and transferred tothe receiver input of a reader. The "forward" signal of the transmitter, which is stronger3.9.4 EPC Gen2- An RFID Standard Classification EPC Gen2 is short for EPC global UHF Class 1 Generation 2.
  54. 54. • Initially, two classes of EPC tags—Class 0 and Class 1—existed. An important development has occurred; EPC global member companies have defined a single, next-generation tag standard—UHF Class 1 Generation 2 (Gen 2). •• Read-Only (Type 0): tags that contain permanent data, commonly referred to as "type 0" tags within the EPC standard• Read-Write (Type 0+): a standards-based EPC extension that allows Type 0 tags to be written in real time• Read-Write (Type 1): tags that can be written over by a reader; often referred to as "type 1" tags within the EPC standard• Class 1, Generation 2: Gen 2 tags retain many of the Gen 1 features while offering key performance, capacity, security and RF efficiency advantages over Gen 1 tags. EPC global is working on international standards for the use of RFID and the EPC in the identification of any item in the supply chain for companies worldwide. One of the missions of EPC global was to simplify the Babel of protocols prevalent in the RFID world in the 1990s. Two tag air interfaces (the protocol for exchanging information between a tag and a reader) were defined (but not ratified) by EPC global prior to 2003. These protocols, commonly known as Class 0 and Class 1, saw significant commercial implementation in 2002-2005. In 2004 the Hardware Action Group created a new protocol, the Class 1 Generation 2 interface, which addressed a number of problems that had been experienced with Class 0 and Class 1 tags. The EPC Gen2 standard was approved in December 2004, and is likely to form the backbone of RFID tag standards moving forward. This was approved after a contention from Intermec that the standard may infringe a number of their RFID related patents. It was decided that the standard itself did not infringe their patents, but it may be necessary to pay royalties to Intermec if the tag were to be read in a particular manner. The EPC Gen2 standard was adopted with minor modifications as ISO 18000-6C in 2006 3.10 CURRENT USES • Passports The RFID chips store the same information that is printed within the passport and also include a digital picture of the owner. The passports incorporate a thin metal lining to make it more difficult for unauthorized readers to "skim" information when the passport is closed.
  55. 55. • Transport payments RFID cards can be used to pay for public transit. It is used in many countries.• Product tracking Cattle Identification ca be done using RFID tags as a replacement for barcode tags.The tags are required to identify a bovines herd of origin and this is used for tracingwhen a packing plant condemns a carcass High-frequency RFID tags are used in library book or bookstore tracking,pallet tracking, building access control, airline baggage tracking, and apparel andpharmaceutical item tracking. High-frequency tags are widely used inidentification badges, replacing earlier magnetic stripe cards. These badges needonly be held within a certain distance of the reader to authenticate the• AutomotiveMicrowave RFID tags are used in long range access control for vehicles.Ford, Honda, and several other manufacturers use rfid-equipped ignition keys as anti-theft measures.• Animal identification Implanted RFID tags are also used for animal identification. There are several moreor less incompatible systems.• RFID in inventory systems An advanced automatic identification technology such as the Auto-ID systembased on the Radio Frequency Identification (RFID) technology has two values forinventory systems. First, the visibility provided by this technology allows an accurateknowledge on the inventory level by eliminating the discrepancy between inventoryrecord and physical inventory. Second, the RFID technology can prevent or reduce thesources of errors. Benefits of using RFID include the reduction of labor costs, thesimplification of business processes and the reduction of inventory inaccuracies.• Human implants Implantable RFID chips designed for animal tagging are now being used inhumans.
  56. 56. Security experts are warned against using RFID for authenticating people due tothe risk of Identity Theft. Due to the resource-constraints of RFIDs it is virtuallyimpossible to protect against such attack models as this would require complex distance-binding protocols.Hand with the planned location of the RFID chipJust after the operation to insert the RFID tag was completed• RFID in libraries Among the many uses of RFID technologies is its deployment in libraries. Thistechnology has slowly begun to replace the traditional barcodes on library items (books,CDs, DVDs, etc.). However, the RFID tag can contain identifying information, such as abook’s title or material type, without having to be pointed to a separate database• Sensors such as seismic sensors may be read using RFID transceivers, greatly simplifying remote data collection.
  57. 57. IV.PART CPROJECT DESCRIPTION-TECHNICAL IMPLEMENTATION OF RFIDSYSTEMS4.1 Serial Port Communication4.1.1 Why Visual Basic? Within the last ten years, Visual Basic has become one of the most popularlanguages for developing business and enterprise applications. In large part, the successof Visual Basic is due to its ability to hide technical complexity and allow developers tofocus on the big picture. With Visual Basic, developers can create software that meets theneed of their business or their customers without getting bogged down in low-leveldetails like memory management and communications interface implementation Serial communication is a popular means of transmitting data between acomputer and a peripheral device such as a programmable instrument or even anothercomputer. Serial communication uses a transmitter to send data, one bit at a time, over asingle communication line to a receiver. You can use this method when data transferrates are low or you must transfer data over long distances. Serial communication ispopular because most computers have one or more serial ports, so no extra hardware isneeded other than a cable to connect the instrument to the computer or two computerstogether.4.1.2 MSComm Control The MSComm control provides serial communications for an application by allowingthe transmission and reception of data through a serial port.SyntaxMSCommThe MSComm control provides the following two ways for handling communications: • Event-driven communications is a very powerful method for handling serial port interactions. In many situations you want to be notified the moment an event takes place, such as when a character arrives or a change occurs in the Carrier Detect (CD) or Request To Send (RTS) lines. In such cases, use the MSComm