Design And Analysis Of Uhf Band Antennas For RFID System

As one of the ten high technologies, RFID technology has been widely used in the commercial automation, industrial automation, transprotation management and many other fields. UHF band is the most suitable band to make extensive use of RFID technology in goods circulation. Therefore, the research of high-permormance UHF band RFID antennas is the necessary assurance to expand RFID technology around the world. The antennas applied in UHF band RFID system is researched in this paper.This dissertation focuses on the design of the broadband tag antenna and metallic tag antenna and the miniaturization design of the reader antenna in the UHF band RFID system. Etching different slots on the radiation patch can prolong the current path in order to reduce the antenna size. Cascade inductance can be introduced in the antenna equivalent circuit by etching slots to realize the matching between the antenna and the tag chip. So a good impedance bandwidth can be obtained. Opening proper slots on the floor is used to improve the antenna gain.In this paper, a novel broadband tag antenna across the entire UHF band (840-960MHz) is presented by etching T-shape slots on the radiation patch to broaden the operating bandwidth. The antenna structure is simple without any via-hole or shorting plate. The operating bandwidth was ensured while the antenna was miniaturized, with a small size of only 33mm×25mm×1.6mm, which is smaller than the antennas in the literature that have been published. The impedance match between the antenna and the tag chip can be tuned conveniently by changing the sizes of the slots. The antenna was fabricated and tested. It can be seen that the measured curve of the input impedance is basically the same as the simulated.In the design of UHF band RFID metallic tag antenna, a novel symmetric T-shape slots antenna across the entire UHF band (840-960MHz) is proposed, with the total size of 30mm×110mm×1.6mm. Compared with the same type antennas in the literature, the antenna size is reduced 45% and the communication distance is prolonged about 1m when the antenna is posted on the same metal surface. The symmetric T-shape slots and the insertion feed structure make the impedance match between the antenna and the tag chip convenient. The antenna was fabricated and tested. It can be seen that the measured curve of the input impedance is basically the same as the simulated, while the measured curve offsets about 120MHz to the lower frequency.The improved reader antenna is proposed by etching slots on the radiation patch to reduce the antenna size and etching slots on the floor to improve the antenna gain. The circular polarization was ensured while the antenna was miniaturized, with a small size of 80mm×80mm×3mm, which is reduced 21% compared with the reference antenna. And the antenna gain is higher than the reference antenna. The bandwidth of 3dB axial ratio covers 920-925MHz which is one of the UHF bands in China.