Anti-collision Study Of The Correlation Inter-digital Transducer Based Surface Acoustic Wave Tag

Radio Frequency Identification(RFID)system based on Surface Acoustic Wave(SAW)tags has a wide range of applications.However,multiple tags may be excitated at the same time and produce simultaneous reply signals which causes the “collide problem” and makes it hard to identify the objects correctly.Thus,this thesis summarizes several methods for solving the SAW RFID anti-collision problem at home and abroad,and analyzes the principle,the research status and existing main problems of each method.On this basis,a Correlation Inter-Digital Transducer(CIDT)based SAW tag is designed,which provides a new method for solving the anti-collision problem.The anti-collision performance of the tag is studied through theoretical analysis,simulation,physical test and system test.It verifies the feasiblity of using the CIDT based SAW tag to solve the anti-collision problem,which makes it possible to expand the application range of the SAW RFID system.Furthermore,the MATLAB simulation model,the COMSOL simulation model and the ADS semi-physical testing platform established in the study process are all be proved to be reliable for the design,optimization and performance test of the anti-collision tag and each has unique application value,which provides a set of complete,convenient,valid and low cost research methods for the optimization design and the performance analysis of the anti-collision tag.At the aspect of theoretical analysis,the anti-collision principle of the RFID system using the CIDT based SAW tag is analyzed primarily by comparing to the typical SAW RFID system.Then,the code structure,correlation property,symmetry problem and sparse inter-digital electrode problem of the CIDT which is the core cell with anti-collision property of the tag are studied.At last,the key design parameters of the tag are discussed.At the aspect of simulation design,the anti-collision coding scheme is designed by utilizing the MATLAB software firstly.And a ? function based simulation model is established in the same software to investigate the auto-correlation excitation signal and the anti-collision property of the tag.Secondly,a 2D finite element model is established to optimize the structure design of the tag in the COMSOL software.Finally,17 different types of tags are designed for fabrication according to the simulation results.At the aspect of experimental measurement,a semi-physical testing platform is build to study the symmetry problem and sparse inter-digital electrode problem of the CIDT and the auto-correlation and anti-collision property of the tags firstly,which picks out the tags with good anti-collision performance to constitute an anti-collision tag group.Then,two kinds of anti-collision SAW RFID system—— semi-wireless system based on two port tag and wireless system based on one port tag are designed.By using the above anti-collision tag group chose by the ADS and the homemade reader,practical testing systems are established to measure the anti-collision performance of the two systems.