Research On A Strain Sensor Based On Rectangular Micro-strip Patch Antenna

Load-bearing structures are the most common structural components in high-end equipment.The loading and stress concentration will easily initiate cracks,leading to structural failure.Meanwhile,the real-time monitoring of strain is essential for the health evaluation of structures.In this paper,based on the mechanism of rectangular micro-strip patch antenna(RMPA)and the electromagnetic field theory,a new type of RMPA strain sensor is proposed.The main research content is as follows:(1)Study of RMPA's mechanism.Combined with RMPA radiation electromagnetic field and transmission line theoretical model,the influence on the natural resonant frequency by the dimension of the RMPA and strain is revealed.The shorter operating wavelength,the higher frequency and the smaller size.The relationship between the resonant frequency offset and the strain is explored,which provide the theoretical basis for the strain measurement.(2)Development and measurement of RMPA.The size of the RMPA affects its natural resonant frequency.According to the influence of the geometric size of patch antenna on its inherent resonant frequency,numerical simulation and theoretical analysis are carried out,and the performance of the sensor is tested by microwave detection system.Four groups of RMPA with different sizes are designed.The influence of the length,width of patch and the feed position on the resonant frequency is discussed.The results show that the resonant frequency is the most sensitive to the change of radiator length,and decreases with the increase of length.The test results are in agreement with the simulation results,and the feasibility of the strain measurement use RMPA is verified.(3)Detection of metal substrate strain.By the resonant frequency and strain of the interaction mechanism,when the metal grounding plate strain change,the resonant frequency will be changed due to the size of the patch antenna changed.In addition,the frequency shift is linear with the strain.The strain of the cantilever plate and the tensile strain were measured in contact and wireless method.(4)Wireless detection and horn antenna.Based on the contact detection of the resonant frequency,the backscatter signal received by the network analyzer is studied.The wireless measurement of the resonant frequency of the patch antenna in two terminal conditions is realized by the microwave wireless measurement system.Two frequency domain signals are structured after anti-fourier transform to eliminating the noise signal.After windowed and other processings,to achieve the resonant frequency extraction,which is of great significance to the real-time monitoring of the passive and wireless of the load-bearing parts.