The Design Of Coder-decoder And Analysis Of Air Interface Performance In RFID System

RFID (Radio-frequency identification) is an automatic wireless data-collection technology with a long history that can be traced back to the late 1940s. Since then, RFID has significantly advanced and experienced a tremendous growth due to developments in integrated circuits and radios. Recently, there are increased interesting in UHF RFID from many fields, such as logidtics, commerce and trade and so on. But it always working in a hostile environment, the readers are easily interfered by noise, therefore seriously influenced its large-scale commercial applications. Based on above reason, it's of great significance to the research and improvement of UHF RFID system. However, due to there are many shortage of hardware exploration, such as the long period for design, complicated procedure for manufacturing, expensive and difficulty for correction. Meanwhile, the software design can solve above problems.The first, this paper investigates the forward link and return link data encoding method and modulation method according to types A, B and C in ISO/IEC18000-6, the power spectral dendity of modulation and encoding were characterized by analysis and calculation, and the advantages and disadvantages of ASK, DSB-ASK, SSB-ASK, PR-ASK and PSK, the antinoise ability and encoding methods of PIE, FMO, Manchester, Miller coding were compared. The second, based on the virtual instrument technology as the foundation, we designed the code-decode method on Lab VIEW, and in decoding design with multi-point sampling averaged method to eliminate noise effects, as the sensitive of FMO encoding, we gave a effective decode methord Specifically, it can reduce the design requirement of filter, and fially gave the result of testing of a data with noise. All of these facts prove software design for data quickly coding, and can correctly decoding to restore information. In the end, we analyse the principle and software realization of cyclic redundancy correction codes (CRC). This design can not only be applied to the RFID testing system, but also provide the reference for commercial RFID reader in order to improve its accuracy.