Research On Surface Acoustic Wave Tag And Frequency Sweep Signal Source

Radio Frequency Identification based on surface acoustic wave is passive, wireless andtamper-proof, it has long identification of distance, can works in harsh environment, so it becomes aresearch hotpot in the RFID field. The thesis focuses on the RF tags based on surface acoustic wavetechnology, including the simulation, design, production and testing of tag chip and tag antenna. Onthis basis, the thesis also studys frequency sweep signal source of surface acoustic wave reader basedon frequency domain sampling.First, the thesis introduces the theory of SAW RFID technology, studys the features and functionsof each part of the SAW tag, compares the advantages and disadvantages of pulse amplitude codingand pulse position coding, analysises the working principle of the two kinds of readers based on timedomain sampling and the frequency domain sampling separately.The static analysis, modal analysis and harmonious response analysis on tag chip IDT ispresented using finite element software COMSOL; the reflectors of the tag are simulated based "themethod for analyzing waves"; and the effect of reflectors’ electrode number, electrode thickness anddeposited gold on reflectivity is analysed; based on simulation analysis, the tag chip is designed,including the material of the piezoelectric substrate, interdigital transducer, reflectors and the tagencoding scheme, etc; tag chip is tested after fabrication, the performance of the tag chips are testedfrom three aspects: the characteristic frequency, the tag encoding and the conformance of the echoamplitude. The test results are consistent with the design requirements, proving the correctness oftheoretical analysis and simulation studies. The thesis also design a frequency domain-time domainconversion software, the frequency response acquired from Network Analyzer can be converts to timedomain echo characteristics of tag chip.Based on tag chip’ research, tag antenna is simulated and designed using the finite elementsoftware HFSS. The structure parameter including arm length, arm width, substrate thickness as wellas the performance which includes return loss, VSWR is optimized; the tag antenna’s S11curve, theVSWR curve and the Smith chart is tested after fabrication, test results verify the effectiveness of thesimulation and design; impedance matching network is designed for the tag chip and tag antenna, andthe three parts are welded together, forming a SAW tag, the tag is tested wirelessly, the performanceof SAW tags is inspected.The thesis designs SAW reader based on frequency domain sampling, and focuses on the study of frequency sweep signal source. frequency sweep signal source uses direct digital frequencysynthesis (DDS) and phase-locked loop (PLL) as frequency synthesizer, the frequency synthesiscircuit board and the power amplifier circuit board is designed and frabricated, DDS, PLL, poweramplifier circuit and sweep signal are tested respectively, the test results verify the correctness of thesignal source’s design.Finally, the thesis summarizes the research work on the topic, points out the shortage of researchwork and provide an outlook of the future work.