The Research Of Tag Identification Performance In Passive UHF RFID System

As an emerging automatic identification technology, radio frequency identification (RFID), which is un-contact and two-way communication, uses RF signals to transfer data and identify objects by coupling between electromagnetic waves. Compared with other identification technologies, RFID has many outstanding merits, such as long identification distance, large data capacity, operate easily, safe, reliable and so on. These features make RFID vast available and great commercial potential. As RFID technology has been widely used, the working performance of RFID system had set higher requirements for its using scope is increasing and the working environment is getting more and more complex.As the interface of RFID system, the tag antenna, which plays pivotal roles in determining the characteristics of the whole system, is one of the most important elements to keep a better communication with the reader. The identification performance of tag is largely determined by the tag antenna, especially in passive UHF system. So the research on the tag antenna has an important theoretical significance and practical value.This dissertation firstly introduced relative knowledge about RFID system, which included the structure of the system and its operational principle, etc. Secondly, it described some basic theory on antennas, like the parameters which decided antenna characteristics and the theories of antenna’s radiation, reception, scattering. And then the operational principle of passive UHF RFID tag was analyzed by using radar scattering principle based on the power transmission. Thirdly, when the factors that affected the identification performance of tag were studied, it had put an emphasis on the analysis of the identification performance of the tag by radar cross section (RCS). And the RCS was proved as one of the key factors on the performance of the tag in theory. Finally, it presented a new method to calculate the identification distance of the tag based on RCS. By using the high-frequency electromagnetic simulation software FEKO on modeling and simulating of the tag antenna, two kind of commercial UHF passive RFID tag which work in the frequency band of860～960MHz were as examples to compute the maximum identification distance. Then compared with the measured parameters, the results coincide with the actual parameters, as well as its reference to the identification performance of the tag. Therefore, this thesis studied the performance of UHF RFID tag. Through theoretical analysis, electromagnetic simulation and actual measurement, it analyzed the major factors that affect the identification performance of RFID tag. Finally, some referenced suggestions, which will be the development and production of RFID tags, had been put forward. Especially on the tag antenna design has a very important theoretical and practical significance.