On The Microwave Radio Frequency Identification (RFID) Techniques

For the requirements of remote information management and mobile business, the microwave radio frequency identification (RFID) technology is studied in this dissertation, with the automatic train identification system of the National Ministry of Railroad as a background. The fundamentals associated with RFID system in the field of electromagnetics and communications are summarized and the technical essence is pointed out at the viewpoint of system design. The main contributions of the author's are as follow.Firstly, the first visual reader or tag detector is developed successfully. The performance detection and analysis of the tags are realized. The reader is integrated with the functions of microwave transmitter, receiver, data collector, digital signal processing (DSP), spectrum analyzer, field strength meter, and encoding. This achievement is appraised by the National Ministry of Railroad, which fills the national blank and reaches the leading level in the world. This product has been applied in practice.Secondly, a microstrip antenna used in portable reader and the two novel tag antennas which are a dual-band dipole antenna and a circular polarized microstrip antenna are developed. The analysis and design of tag detector are presented. The characteristics of the tag are improved and the tag obtained use in practice.Next, the techniques of DSP with high-speed and high-accurate and floating point processing are successfully applied in the area of microwave radio frequency identification. This makes real-time collection and FFT transform and display possible, and the tag's performance is analyzed quantificationally in time domain and spectral domain.Moreover, the canceling technology of two microwave signals with same frequency is applied in microwave RFID system firstly, and the method for improving the isolation between the transmitting channel and receiving channel is obtained. The isolation of the reader is increased for more than 30dB by several experiments.Finally, Some methods of digital processing techniques, such as polynomial curve fitting and exponential curve fitting and subsection curve fitting, are used firstly to compensate the performance of the detector. The measurement accuracy of the reader is improved, with the validity proved.