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  • 1. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 4, June 2012 13.5 MHz RFID(NFC) ANTENNA DESIGN FOR DEDICATED MOBILE APPLICATIONS WITH IMPROVED RESULTS 1 2 3 1 Amit Gupta , Sudeep Baudha , Shrikant Pandey 2 3,, Department of Electronics & Communication, Gyan Ganga College of technology, Jabalpur (M.P)Abstract—First part of the paper discusses antennas can be created by exploiting realabout the latest trend within RFID is to use life metallic structures. In this paper, athe technology for more advanced applications shopping trolley is taken as an example. Thethat can replace the magnet cards used today first part of this paper will focus upon thefor payment and electronic key cards. The design of NFC antennas for communicationmore advanced types of these cards, called between two devices within proximity lessproximity cards. This standard, named NearField Communication (NFC) can therefore be than 10cm apart. Such example in the caseused to replace key cards and of contactless payments would be a mobileVisa/MasterCard. At the same time, a small handset communicating with a vendingNFC reader integrated in the phone opens up device, such as a ticket machine or creditfor many new possibilities. If this idea is card payment terminal in a café. Applyingaccepted by consumers and companies, the cell theory analysed for such antennas, the paperphone could be the only device needed when a will then go on to analyse the potential useperson leaves the house, since it in addition to of a shopping trolley to act as a roguebeing a phone also is a set of keys, an ID card antenna from which information couldand a wallet. potentially be eaves dropped. Later part of paper discuss about the RFIDantenna and its revolutions. New designs withnew results and all other parameters todescribe the antenna design in detail. 2. NFC ANTENNA DESIGN THEORY:- A typical example of magnetic couplingINTRODUCTION:- loop ntennas, otherwise known as “H-The increasing interest in using Near Field antennas”, is illustrated in figure 1. The twoCommunications (NFC) technology at ends of such an antenna are connected to a13.5MHz is growing rapidly in the area of radio frequency (RF) transceiver with acontactless payments, as well as numerous capacitor placed across in parallel. The DCother applications, between devices that are resistance at the input can be assumed to bewithin 10cm distance apart. However, there zero while as the frequency increases, it willis growing concern that the use of such create an inductance such that a circuitdevices for contactless payments invites model for such an antenna can beproblems with regards to using metallic represented as that shown in figure 2 whereobjects in the vicinity of the two devices to theact as “rogue” antennas, which eavesdrop Antenna is represented as an inductor [2].information during a financial transaction is The parallel capacitor is then connected totaking place. This paper presents aspects of the load of the transceiver, which will in thisdesigning H-antennas both for the two case be assumed to be purely resistive. Weredevices communicating while also there to be a reactive component at theidentifying the means by which rogue transceiver input, it can be easily cancelled out by applying a series, negative reactance 210 All Rights Reserved © 2012 IJARCET
  • 2. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 4, June 2012so therefore need not be considered. Manypublications in the literature assume theinductance to be constant over frequency,though observations from measurementusing a network analyzer find it to be thecase that inductance will change at lowerfrequencies.Figure 3 shows measured results using a Fig.2 circuit model of H antennavector network analyzer, where theinductance reduces to a constant value afterabout 1MHz. Where the frequency is low,the loop effectively resembles a short circuitwhere the inductance would be expected tofall to zero. However, due to precisionrequired in such circumstances, an accuratevalue of inductance cannot be resolved. Inthis paper the inductance will be consideredas frequency dependent and is therefore Fig. 3 Measured values of inductance overdenoted, L(f) or L(w) where relevant, where frequencyf is the frequency and w is the angularfrequency equal to 2pf. This will become At the resonant frequency, the transceivermore important when the inductance values connected to the antenna has a loadfor a rogue antenna are considered. For any resistance, RL, where in receive mode it willloop antenna to resonate, it is well known have the following system frequencythat the parallel capacitance to be applied response function, based on the ratio of thecan be derived as follows: load voltage, VL, across the load resistance compared to the input voltage effectively resulting from the current flowing in the loop antenna, Vin, is defined as follows: One important point to realize from this is that maximum power transfer at the resonant frequency, w0, will reduce to:Fig.1 Coil Antenna thus requiring a low inductance in order to maximize gain with as high load resistance as possible. The magnitude of this equation 211 All Rights Reserved © 2012 IJARCET
  • 3. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 4, June 2012is also equal to the Q factor of the system, transmitting RF signal when operatingthat will depend on a low value of L and a active and passive NFC mode and RFIDhigh value of RL. For transmit mode, the reader mode. The Tag part is both for targettransfer function relating the voltage across operation of NFC protocol and passivethe antenna, VA, which is now a reactive RFID tag mode. The conventional NFCload, to the source voltage, VS, that is now chipset could not support RFID tag modein parallel with RL, is as follows: when external power is not supplied, because it has only one antenna both for NFC mode and RFID mode [5]. RFID tag mode must support standard of 13.56MHz smartcard such as ISO/IEC14443 type A/B, or ISO/IEC15693[1-4]. The key differences between target of passive NFC mode and3. BLOCK DIAGRAM OF THE RFID tag is operating distance, data rate,PROPOSED NFC TRANSCEIVER. and host interface.To realize NFC devices, implementation of 4. SIMULATION USING ADS:-active and passive mode of NFC protocolwith passive RFID protocols is required. An The designed coil antenna has 10 numbersNFC chipset consists of a digital block of turns in units of 100x50.including digital controller and hostinterface, and an analog front end part withexternal antenna matching circuit as shownin figure: Fig. 5 Schematic diagram of the antenna coil It has got lumped ports to deal with power supply. The gap between the coils is 1 mm and the thickness of the coil is also 1 mm. ADS view of designed coil:-Fig.4 Block dig of NFC transceiverThe host interface of the chipset should bedesigned to support maximum baud rate of424kbps. The analog front end part iscomposed of two analog/RF circuits andmatching circuits for Initiator and Targetantennas. The reader/writer part is for Fig. 6 ADS coil design 212 All Rights Reserved © 2012 IJARCET
  • 4. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 4, June 2012 The Input impedance (ZL) in the schematicReturn losses achieved by simulation:- of the ADS with lumped elements:- Fig. 10 S-parameter matching circuitFig.7 Return losses Gain parameter achieved:--16.78dB is achieved at 13.5 MHzfrequency. This is almost the double ofexisting system of NFC.Smith chart:- Fig. 11 Gain & directivityFig 8 Smith chart for the coil antenna 5. CONCLUSION:-3-D plot:- This paper shows the basic parameters of NFC system and antenna design, including all the circuits and values required for designing the antenna. In later part the simulation work has been shown which was done using ADS software. With the help of this software many parameters have been taken out eg. Antenna design, Return losses, S-Parameters, Gain,Fig. 9. 3 dimensional view Directivity & 3-D plot. The existing NFC system provides a distance of 3-4 Cms. 213 All Rights Reserved © 2012 IJARCET
  • 5. ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology Volume 1, Issue 4, June 2012Maximum between two NFC tags with About Authors:-return losses in range of -8 dB. With this new design of 13.5 Mhz RFID About Authors:-antenna, it will double the distance thanbefore that means two NFC tags cancommunicate with more than double AMIT GUPTA: BE (EC) from GGITS,distance as compared to what they are JABALPUR.M.Tech. (UnderPersuation)currently using. This will be helpful in DigitalCommunication, GGCT, JABALPUR.several NFC applications which enhance the Research Work:-Antenna Designing.transmission and overall efficiency of thesystem.6. REFERENCES:- Sudeep Baudha: B.E. (EC) GEC,Ujjain.M.Tech. (Microwave EnggIIT[1] Near Field Communication-White paper, Kharagpur. search Work :- AntennaECMA DesigningInternational, Jan. 2004.[2] International standard ISO/IEC 18092,InternationalStandardization Organization, April 2004.[3] Standard ECMA-340, “Near Field Shrikant Pankey : BE (EC)Communication - TIETECH,JABALPUR.Interface and Protocol (NFCIP-1)”, ECMA M.Tech. (Under Persuasion)International, DIGITAL COMMUNICATION, GGCT,December 2002.[4] Standard ECMA-352, “Near Field JABALPUR.Communication Interface Research Work :- Antenna Designing.and Protocol -2 (NFCIP-2)”, ECMAInternational, December2003.[5] Short Form Specification, “Near FieldCommunication PN531- μC basedTransmission module”, PhilipsSemiconductors, February 2004.[6] David M. Pozar, Microwave Engineering3rd ed, Publishing House of ElectronicsIndustry , pp. 223-235, September 2006. [7] Antenna Theory and Design by Balanis,3rd edition. 214 All Rights Reserved © 2012 IJARCET