Research On Saw Tags With Hybird Error Control Ability And Large Code Capacity

Surface Acoustic Wave (SAW) Radio Frequency IdentificationTechnology is passive, wireless, good reading speed, low cost and candirectly used as temperature or pressure sensors etc. With so manyadvantages mentioned above, SAW RFID technology can worked as thecomplement of IC RFID technology. But a problem is that data integritycannot be guaranteed as SAW tags is a truly passive device. This probleminfluenced the widespread of SAW RFID.To protect data integrity of SAW tags, redundant information shouldbe added to achieve error control function. Code capacity of somemodulation methods like On-Off keying (OOK), Pulse PositionModulation (PPM) and Multi-Pulse Position Modulation (MPPM) evencannot satisfy the demands of EPC GLOBAL. Till now, only TimeOverlapped pulse Position with simultaneous Phase offset modulation(TOPPS) with Cyclic Redundancy Check code was mentioned.This paper introduced and analyzed the principle of Hamming code,Cyclic Redundancy Check code and Reed-Solomon code in order to solvethe problem of protecting data integrity. Above these three error controlcodes, redundant information should be added to achieve error controlfunction. Reed-Solomon code is a kind of forward error correction codeand could be used for non-binary information. Besides, with theoutstanding characteristic as powerful error correction capability anddecoding methods, Reed-Solomon code is well-suited for passive SAWtags.The realization of error correction function needs a larger coding capability. By compare four modulation methods: OOK, PPM, MPPM andTOPPS, This paper proposed a new method which uses Phase DelayLength Limited Modulation method on the basis of Reed-Solomon code.After that, this paper discussed and solved the problems in thecombination of PDLL and Reed-Solomon code. To make this new methodmore practicable, hybrid error correction proposal was proposed to replacethe forward error correction proposal. Then, a simulation with Monte Carlomethod about this method was given.Finally, a stress test with real SAW tag was introduced.