The Encode And Decode Technology Of A Saw Tag With Error Correction Code

Surface Acoustic Wave (SAW) tag is a kind of passive tag. It can perform better in harsh environments than other passive Radio Frequency Identification (RFID) tag.However, compared with IC RFID tag, there are some factors limited the development of IC tag such as limited code capacity and no error correction function. Thus, this paper is focus on a SAW tag with error correction code and large coding capacity and the encoding and decoding technology.First, we introduced the basic principle of main modulation method: MPPM (Multi Pulse Position Modulation), TOPPS (Time Overlapped Pulse Position with simultaneous Phase offset modulation) and PDLL (Phase Delay Length Limited Modulation). Then we compared the code capacity of this method and reach the conclusion of PDLL is much better than the other methods. Also, this conclusion provided a theoretical basis for a SAW tag with error correction code and larger code capacity.Then the focus of this paper is given: design of a SAW tag with error correction code. To improve the data integrity, we combined the Reed-Solomon coding with PDLL modulation method, which has improved the query efficiency of the system.After that, we analyzed different methods of estimation group delay. They are: the definition method, improved definition method and the analytic cross-correlation method. And then we simulate and manufacture tags with TOPPS modulation. After temperature compensation and signal processing, we discussed the group delay accuracy with the mentioned method.Finally, a brief description of the SAW RFID system testing process and test results are given.