Design And Optimization Of Saw Pressure Sensor

Surface Acoustic Wave(SAW)devices have the advantages of high accuracy,small size,strong anti-interference ability,and passive wireless,etc.With the research of SAW sensor devices with different working principles,the application prospects are getting wider and wider.Different applications have different requirements for the performance of the device.Therefore,the optimization of the performance of the SAW devices,the design of the matching antenna to achieve the passive wireless function,and the research of the signal transmission circuit design direction have important significance for improving the performance of the SAW sensor.This paper mainly studies the surface acoustic wave sensing mechanism,designs the surface acoustic wave pressure sensor,and conducts the theoretical analysis and scheme design of the wireless transmission module matching it.Specific research work is divided into the following three points:(1)Based on the surface acoustic wave sensing mechanism,analyzed the piezoelectric substrate material of the sensor,studied the applicable occasions and scope of different piezoelectric substrates,and determined the selection of substrate materials in SAW sensor device;Based on the analysis of the equivalent circuit model,an interdigital transducer(IDT)structure and a reflective grid structure are designed,and a single pair of IDT model is established.And we studied the effect of different structural design parameters in the IDT on the intrinsic frequency of the SAW device,and COMSOL software is used to model and analyze the IDT,establish a parameter fitting curve,consider the processing technology and model errors,and optimize the IDT structural design parameters with an intrinsic frequency of 914.99 MHz.The stress-strain and piezoelectric effects of the base material are analyzed by the finite element algorithm to determine the actual etching position of the sensor IDT structure and the reflective grid.By testing the actual processed substrate,the working performance of SAW pressure sensor is analyzed.(2)In order to solve the signal transmission problem of surface acoustic wave pressure sensors,we analyzed the antenna design performance parameters and antennatheory research.Combined with the SAW working principle,a surface acoustic wave transmission matching antenna is designed.HFSS software was used to simulate the influence of the antenna structure length on the operating frequency and characteristics,and to determined the specific structure size of the signal transmission antenna.The antenna was designed with a working bandwidth of 105 MHz and an antenna impedance of(50.335 + 2.095j).Then through the research of antenna miniaturization technology,the design antenna is miniaturized,and the antenna design with an operating bandwidth of84 MHz and an impedance of(50.845 + 4.535j)at 915 MHz is obtained.(3)In order to solve the problems of surface acoustic wave pressure sensor with high working frequency and low accuracy of signal acquisition in high frequency band,a surface acoustic wave signal conditioning circuit is designed in this paper to improve the signal acquisition accuracy of SAW devices.The two-way signal transmission circuit reduces the interference caused by the external environment.The signal is mixed to reduce the signal frequency band and reduce the interference of high-order clutter.The signal processing circuit is then used to ensure the accuracy of the SAW measured variable through circuit design such as filtering,amplification and shaping,and to increase the readability of the measured variable.Finally,the design circuit is analyzed and simulated by the Multisim high-frequency design software.The results prove that the signal conditioning circuit model established in this paper has good signal processing ability.