Study Of Metamaterial-Inspired Uhf RFID Tag Antenna

With the rapid development of electronic commerce, the requirements for efficient logistics increase constantly. RFID system is drawing more and more attention due to its advantages in cost and efficiency. Based on this requirement, tag antenna, which is the main part of the RFID system, is studied in this paper. Metamaterial-inspired near-field resonant parasitic (NFRP) element is introduced in the design of tag antenna in order to decrease the cost and improve the applicability of RFID system.Firstly, the domestic and foreign research situation of tag antenna and metamaterial-inspired electrically small antenna is presented. Then, the working principle and classification of RFID system and some common parameters of UHF RFID tag antenna are presented. Then, the basic theory of metamaterial-inspired electrically small antenna and its value for tag antenna are also presented. Based on these theories, the metamaterial-inspired NFRP elements are introduced in UHF RFID tag antenna. Three types of metamaterial-inspired UHF RFID tag antenna are proposed and analyzed. An equivalent circuit, which is based on complex impedance, is derived to help tune the parameters of the antenna. The structures, sizes, parameters and tuning methods are all presented.The results show clearly, by introducing the theory of "metamaterial-inspired", that the proposed tag antennas have the advantages of small size, low profile, good omni-direction, easy tuning and low cost.