The Investigation Of The Dual-mode Surface Acoustic Temperature Sensor Based On LGS

Sensors are an indispensable part of modern industrial production,transportation,electronic information,aerospace and many other fields.Sensors provide accurate measurement information and the ability to obtain instant messages,which can increase the efficiency of the system and ensure the stability of the system.The manufacture of miniaturized sensors that can be used in harsh environments is a very important research direction.Because SAW resonators have the advantages of simple design,small size,and passive wireless testing,they have a wide range of applications in various fields.In this paper,we firstly use COMSOL software to simulate the vibration modes and frequency characteristics of Rayleigh wave mode and Bulk wave modes of devices with different line widths and substrate thicknesses.It is concluded that the resonant frequencies of the bulk acoustic wave and the Rayleigh wave change proportionally with the change of the line width of the interdigital device,and the intervals o f the resonant peaks of the bulk acoustic wave mode increase with the increase of the line width;the Rayleigh wave vibration is mainly concentrated in The surface of the piezoelectric substrate,and the bulk acoustic wave mode vibration is distributed throughout the piezoelectric substrate.At the same time,under the conditions of a substrate thickness of 500?m,the larger the line width,the larger the interval between the modes of the bulk wave.When the line width is 2?m,the difference between the first three modes of the bulk acoustic wave is 0.15MHz,and when the line width is10?m,the difference is 0.813MHz.Secondly,the temperature and frequency characteristics of the Rayleigh wave mode and the bulk acoustic wave mode of a device based on a LGS crystal are investigated.The devices with line width of 2?m,3?m,6?m and 10?m with 100 pairs of fingers are designed.Based on the MEMS technology,they were made into real objects and the temperature-frequency characteristics of their dual-mode were tested.The results show that the resonant frequencies of the two modes are quadratic with temperature,and the second-order frequency temperature coefficients of the two modes are almost equal.Therefore,a temperature sensor with a wide temperature range of linear output characteristics can be constructed using the difference of the dual-moderesonance frequency.Heating from room temperature to 400? and then cooling naturally,the result of the temperature test using the dual-mode difference is basically the same as the test result of the thermocouple,which indicates the practical feasibility of the dual-mode temperature sensor.The strength of the dual-mode resonant peak affects the performance of the device.In order to explore the effect of the line width and the number of interdigitated pairs on the dual-mode resonance peak under the same substrate thickness,devices with line widths of 3?m,6?m and 10?m were designed and the number of pairs of crossmatches was 1,5 and 20,50 pairs and 100 pairs of devices,and tested their performance.It is concluded that as the line width increases,the interval between the modes of the bulk wave increases.Under the condition of the same substrate thickness and the same line thickness,the absolute intensities of the Rayleigh wave mode and the body wave mode increase as the number of interdigitated pairs increases.But the increase of Rayleigh wave resonance peak value is far greater than the increase of body resonance mode resonance peak value.With the interdigital pairs is 100 pairs,the group delay time of the bulk acoustic wave reaches-114.57 ns when the line width is 2?m,the group delay time of the bulk acoustic wave is-6.84 ns when the line width is 3?m,the group delay time of the bulk acoustic wave is-22.81ns when the line width is6?m,the group delay time of the bulk acoustic wave reaches-104ns when the linewidth is 10?m.