Design And Research Of Strain Sensor Based On Passive RFID Tag Antenna

Structural health monitoring(SHM),as a safety measure to prevent structural catastrophic failures,is very important in daily life and industrial fields.Radio Frequency Identification(RFID)technology can realize distributed structural health monitoring due to its advantages of low cost,passive wireless and long reading distance and so on.Tag antenna can be used as a new type of antenna strain sensor with simple configuration and high integration because of its dual functions of communication and sensing.Therefore,this dissertation,which carried out a serious research work on tag antenna strain sensor based on radio frequency identification technology,is mainly divided into two parts.In the first part,based on the basic theory of rectangular microstrip antenna,two kinds of anti-metal tag antenna strain sensors with different feeding structures are studied and designed,which provides guidance for the research and design of tag antenna strain sensor.In the second part,the miniaturization of tag antenna strain sensor is further explored,and the application of tag antenna strain sensor in health monitoring of small size structure is expanded.The specific research contents of this paper are as follows:(1)It is formulated that the theoretical relationship between strain and resonant frequency of circular microstrip antenna and rectangular microstrip antenna in the two different directions based on the principle of microstrip antenna.The sensitivity and linearity of two shape patch strain sensors are compared and analyzed,and the influence of antenna geometric parameters on sensor sensitivity is discussed.Secondly,based on the theory and structure of rectangular microstrip antenna,combined with transmission line model,this dissertation designs a tag antenna strain sensor with short-circuit stub feeding structure,and the performance of tag antenna and the sensing performance of sensor under force-electromagnetic coupling are simulated and analyzed by HFSS and COMSOL software respectively.Additionally,a new low-cost tag antenna strain sensor with H-slot feeding structure is proposed,which can realize full planar processing,and its feasibility as a strain sensor is verified.Then,it is verified that the implement of the two sensors for applications near metallic objects through analyzing the influence of metal surface on the performance of tag antenna.Finally,the influence of model parameters on strain transfer efficiency is analyzed,and the strain transfer efficiency between metal structure surface and two kinds of sensor patches is62.49%and 68%respectively.The antenna performance and sensing performance of two kinds of feed structure strain sensors on metal surface are compared and analyzed,which provides guidance for the research and design of tag antenna strain sensor.(2)The miniaturization of tag antenna strain sensor is studied and designed.Firstly,based on H-slot-feed tag antenna sensor,interdigital slot structure and butterfly structure tag antenna strain sensors are proposed through meandering technology and loading technology.The impedance matching design of the miniaturized tag antenna is completed on condition that the gain is-9dbi atj=0 ~o,q=0~oto meet the reading distance of the small size structure.The overall size of the strain sensors with interdigital slot and butterfly structure is reduced by 74.35%and 71.65%after optimizing,and the goal of miniaturization is achieved.By comparing and analyzing the simulation results,it is concluded that the butterfly tag antenna sensor has higher sensitivity and lower return loss S11.Finally,according to the two-port network equivalent test principle and method of tag antenna,the impedance and sensing performance of two kinds of miniaturized tag antenna strain sensors are tested and analyzed by vector network analyzer.The simulation and test results are compared and analyzed,which verify that the performance parameters of the sensor basically meet the design objectives.It makes the tag antenna strain sensor more flexible for more monitoring structures of different sizes,and broadens the application of tag antenna strain sensor in the field of structural health monitoring.