Research And Design Of SAW RFID Tag System

Radio Frequency Identification (RFID) tag based on surface acoustic wave(SAW) is passive, adaptable and has a long identification distance, so it becomes aresearch focus on radio frequency identification technology in China and abroad. Thispaper has a theoretical study on the tag which technology foundation is surfaceacoustic wave, and proposes a kind of SAW tag design.First, the basic theory of SAW tag is systematically introduced. The structure ofthe SAW tag is given, and its technical characteristics were analyzed. The reflectorand the interdigital transducer (IDT) are the fundamental parts of SAW tag. The basicof reflector structure is reflection of a single gate, this article analyzes the reflectioncharacteristic of the individual gate and the coupled-mode theory of the reflector. Thebasic structure of IDT is introduced and four models for simulating the IDT are given.One of the main technical parameters of SAW tag is the coding capacity of thetag. In this paper, three kinds of SAW tag coding modes are introduced, namely on-offkeying coding, phase shift coding and pulse position coding. The coding theory ofthese three coding modes are introduced, and advantages and disadvantages of eachtype of coding modes are analyzed.In the IDT model analysis, this paper presents a model based on the chargedistribution. Firstly, the basic theory is introduced, and then this paper described thismethod by the example of the split finger interdigital transducer. Compared with thecharge distribution simulated by COMSOL software, it verify the validity of thisanalysis method, and then the characteristic of some parameters of the split fingerinterdigital transducer is simulated and analyzed.This paper gives the preliminary design and simulation of the SAW tag. First,select the base material and the metal material of the tag, and then the reason is given.The specific implementation structure of SAW tag using multi-pulse position coding(MPPM) mode is given, and by simulation, the IDT structure of SAW tag use afloating electrode unidirectional IDT (FEUDT).