Research Of RFID Techniques Based On The Polarization Of Electromagnetic Wave

Radio Frequency Identification(RFID) is an emerging contactless automaticidentification technique using radio frequency signal for data communication. In recent years,the cost of RFID systems decreases with the rapid development of microelectronics,integrated circuits and computer. It’s an essential way to analyze the character of EM wavepropagation and channel to meet these requirements.Focusing on the polarization of EM wave, the property of circularly polarized wave andthe linear polarization multiplex are analyzed, and the major contributions are summarized asfollow:1. As several regions have different RFID bands in UHF, a circularly polarizedinverted-F reader antenna is presented to cover all the bands. Meanwhile, two inverted-Fantennas are placed symmetrically on the ground, serving as transmitting and receivingantennas respectively. The isolation between two ports is realized by the method of defectedground structure, which enables this antenna to be a RFID diplex reader antenna without acirculator and simplify system structure.2. It is promising to integrate position detection in RFID system, which provides positioninformation apart from identification. A phase-based RFID displacement and rotationdetection technique is proposed in this paper. The novel technique is designed by analyzingthe phase of RF signal backscattered from a linearly polarized tag illuminated by a circularlypolarized reader antenna.3. In this paper, a chipless tag based on a novel dual-polarized resonator is presentedwhich encodes data into spectrum using resonator structure. The design uses crossed wires tohave independent resonance in the orthogonal directions realizing polarization multiplexing.Using two nesting dual-polarized resonators, the coding capacity of this tag reaches 16 bitswithin a compact surface of 30mm′20mm and the band from 3 to 6 GHz.