Design Of Several Tag Antennas And The Dual-Band Bandpass Filter

As a non-contact automatic identification technique, radio-frequency identification (RFID) technology utilizes radio waves to carry the information of the identified objects or the commands to identify objects by space coupling, such as inductive coupling or electromagnetic wave propagation. Compared with other identification technologies, RFID technology used for identification has many advantages. Meanwhile, RFID antenna plays an important role in the whole RFID system, so the development of RFID antenna is of theoretical significance and practical value for the RFID system. Filter is a critical RF device in the wireless communication system. Many functions, such as mirror interference filtering, noise attenuation, frequency division multiplexing and mixing circuit with high performance requirements, should be realized by filters. With the increasing humanization and broad band demands in the wireless communication, various kinds of filters are fabricated with different structures and characteristics to satisfy the demands of miniaturization and light weight design.In this thesis, the RFID technology is briefly introduced, and the operational principle of RFID systems and their classification are presented. The antennas used in RFID systems are discussed. Then, a trapezoid dipole antenna with high inductance is designed based on the theories of dipole and impedance match. A dual-frequency dipole tag antenna is also simulated and implemented. The measured results show that the performance of the modified antenna is improved, which can be used in dual-frequency RFID systems. Moreover, a microstrip slot antenna with the coplanar structure is investigated. The measured results agree well with those from the simulation.The transmission characteristic, basic theory and design principle of the filters are expatiated, and a dual-band bandpass filter is proposed, which is based on the microstrip mender-line ring dual-mode resonator and the CSRR-DGS structure. Compared with the conventional dual-band bandpass filter, the proposed filter has the advantages such as compact structure and high isolation. The good agreement of the simulation and measured results validates our design.