Design And Research On Tag Antenna Used For RFID System

Radio Frequency Identification is a non-contact automatic identification technology. In particular, because of the advantages of its recognition speed and recognition distance, the UHF band to become a national research focuses. As a key part of RFID system, the research of the tag antenna becomes important. The design requirements of the tag antenna are anti-metal, miniaturization and the impedance match of the antenna with the chip. The research and analysis is based on these requirements in this paper.Firstly, the RFID system, its working band and the applications in each band are briefly introduced. Also, the domestic and international status of the anti-metal and the miniaturization is summarized and analyzed. The basic parameters of the antenna and the simulation software are briefly described. Meanwhile, the parameters, consists of reading distance and the matching of the antenna with the chip is given in this paper. Moreover, the T-matching network is detailed analyzed.Secondly, the summaries of the design requirements for RFID tag antenna are shown in this paper. The influence of the metal in RFID system is analyzed in this paper. An antenna is designed for the metal surface is proposed in this paper. The dimension of the antenna is35x36x3(mm3). The impedance used in this paper is24-j207. A T-matching network is used for the matching between the chip and the antenna. At925MHz, the return loss of the antenna is-25dB.The simulation results show that the antenna has a good match with the chip.-3dB impedance bandwidth of the antenna is10MHz and can be used in the UHF band. According to the radiation patterns, the antenna has the characteristics of omni-direction in the surface of xoy, yoz and xoz. In addition, the structural parameters of the antenna is simulated and analyzed in this paper.the simulation results show that the impedance of the antenna can be changed in the band of (11~39)+j (170~240). So the antenna can be matched with other chip with the impedance in this range.Finally, The SRR (Split Ring Resonator, opening the ring resonator) is briefly introduced. Then the structure of the SRR is used for the purpose of the miniaturization of the tag antenna. The dimension of the antenna based on SRR is30x25x1(mm3), and it achieved the miniaturization of the antenna. Similarly, the T-matching network is used for the purpose of the matching between the antenna and the chip. The chip used in this design is also24-J207. The simulation results show that the return loss of the antenna in925MHz is-50dB, so the antenna has a good match with the chip. The antenna also has a characteristic of omni-direction in the three surfaces. The antenna proposed in this paper is fabricated. The port extension is used for the test the impedance of the antenna. The measurements show that the antenna is basically the same as the simulation. However, because of the processing and the non ideal of the test wire, the wear and tear is existences. The antenna proposed in this paper has the advantage of simple structure, and can be used for engineering. Also, the parameters of the structure are simulated and analyzed. The antenna can be matched with the chip that the impedance is in the range of (15~350)+j(180~420).