| Radio frequency identification (RFID) system is a wireless communication system in which the radio link between the base station and the tags are furnished by the modulated back-scattered waves. It uses a lot of technologies, such as IC, antenna, wireless transceiver, data coding and electromagnetic. Few advantages of RFID are not requiring the transponder to be in line-of-sight, long distance identification, readable and writable tags, multiple tags identification, handle environments like moisture, dirt frost etc. So it is becoming more and more popular.Tag antenna design is one of the key technologies of RFID, especially UHF tags, for its high data transfer rate and high identifying speed as well as long reading and writing distance. UHF tag antenna is playing an increasingly important role in RFID systems, but due to specific application environment in the case of metal and water, impedance matching issue of different IC circuit, and wide bandwidth requirements etc, there are a lot of challenges and difficulties for this subject, and this projest is "863" key project, RFID tag antenna design and research.The performance and specification of different tag labels, tag antenna design mainly one of the widely used passive dipole and its structure changes are introduced in this paper in detail. The capacitive and inductive coupling mechanism is proposed for impedance matching to improve the operating bandwidth of UHF band, base on lots of simulation and testing, the antenna on PET substrate has a bandwidth of 150MHz, which covers 840-960MHz, and achieves a reading distance of 8 meters.Near-field tag antenna technology is studied in this paper also, which has discussed a type of loop-feed antenna working both in far-field and near-field. The antenna has a bandwidth of 130MHz and can operating in the near-field and far-field independently. Besides, 3 different antennas are designed in order to adapt to different chip impedances and ensure good performance. |
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