Surface Acoustic Wave High Temperature Pressure Sensor Based On Lanthanum Gallium Silicate With High Q Value

With the development of science and technology,in the aerospace,energy and chemical industries,more and more attention is paid to the pressure safety monitoring of devices in high-temperature environments,and the demand for high-performance high-temperature pressure sensors has increased.At present,various styles of high temperature pressure sensors have been developed at home and abroad.Traditional pressure sensors already have high stability and reliability,but the technical difficulties about high sensitivity and passive wireless have been unable to break through.Surface acoustic wave sensors have great prospects in the high-temperature pressure sensor market due to their small size,low power,high sensitivity,and passive wireless capability.This article has carried out research on the application of surface acoustic wave pressure sensor in high temperature environment,which has very far-reaching significance and scientific value.In this thesis,a surface acoustic wave resonator as the sensitive element of the pressure sensor and（0°,138.5°,26.6°）cut-type lanthanum gallium silicate as the substrate material is designed for the pressure monitoring requirements in high-temperature environments.Aiming at the high-Q resonator,the surface acoustic wave resonator is designed by theoretical model simulation and finite element simulation,it’s layout is drawn,and samples are successfully produced by Micro-Electro-Mechanical Systems processing technology.According to test requirements of the application environment,this thesis adopts the thimble pressure type structure to package the surface acoustic wave chip,and confirms this structure’s feasibility through COMSOL simulation.Aiming at the sensor test problem in high temperature environment,this thesis proposes a simple and feasible signal extraction scheme,and the experiment has confirmed that the scheme is easy to operate,effective and reliable.Through the pressure and high temperature test platform,the performance test and analysis of the principle prototype have been completed.The experimental results show that the center frequency of the surface acoustic wave resonator is 140.21MHz,the S₁₁ peak value is-14.10d B,and the device Q value is up to 12811.The sensor has good high temperature tolerance and excellent temperature stability in the range of 25～350℃.The first-order temperature coefficient of frequency isα=-1.11ppm/℃,and the second-order temperature coefficient of frequency isβ=-55.01ppb/℃².The pressure sensitivity of the surface acoustic wave sensor is good,and changes linearly in the range of1.5～3.3MPa.The pressure coefficient of frequency is 2.168ppm/psi,and the hysteresis rate is 6.31%.The above results show that the surface acoustic wave sensor studied in this thesis can meet the needs of pressure testing in high-temperature environments,and has high pressure sensitivity and low temperature coefficient.At the end of the article,the problem of improving high temperature and pressure testing is discussed,which lays a theoretical and experimental basis for the realization of passive wireless devices.