Research On Passive And Wireless Temperature Sensor Base On Surface Acoustic Wave Technology

With the development of modern technology, the requirement for environmental temperature measurement also increases, so the temperature sensor needs to be optimized in order to satisfy the complicated environments. Power distribution box is one of the most important parts in the power transmission system. The high temperature due to its long working time could cause a lot of heat from the conversion of electric energy, which could lead to the safety problem. As a result, it is meaningful to monitor the temperature of the power distribution box. The surface acoustic waves(SAW) temperature sensors have the advantages of small size, high accuracy and good calibration stability. Moreover, they can work in harsh environment such as high temperature and high voltage for a long time, which makes them widely used in the power monitoring system.In this dissertation, the author aims to design and fabricate a wireless passive SAW temperature sensor which has high accuracy, reliability and high quality factor. First of all, the principle of SAW temperature sensor is analyzed and the SAW structure type is also determined. Then the wave propagation characteristic on piezoelectric material is studied and the Christoffel equation is obtained. The wave propagation velocities of SAW in different directions are calculated through numerical simulation method using MATLAB software. The resonator is designed based on the calculating result as thus. This paper also investigates the simulation method of the resonator based on the COM theory, achieved the optimization of the parameters and accomplish the admittance simulation of the resonator. A more accurate and efficient method for SAW resonator layout realization improved by using MATLAB program to substitute the traditional modeling method. The sensor package is also designed. Finally, by analyzing the effect of the structural parameters of the resonator on the scattering curve, the characters of the frequency and scattering have been studied. the temperature sensor is calibrated and the temperature sensitivity and hysteresis are also analyzed.In conclusion, the SAW temperature sensor is designed and discussed in this dissertation. The simulation method can also apply for the design of other SAW devices. The results are stimulating for the study of SAW sensor in the future.