Research On Structure Of Passive Wireless Resonant SAW Pressure Sensor

In many special sensing application situations where the sensors cannot be connected by wires or the battery cannot be changed easily, it is necessary to use passive wireless sensors for detecting. As a new kind of sensor, passive wireless surface acoustic wave (SAW) sensors have many advantages to measure parameters of closed and fast moving objects by an untouched way. In addition, passive wireless SAW sensors can work in the inflammable, explosive environments, and apply in places of powerful electromagnetic interference or low temperature. Therefore, the study of passive wireless SAW sensors has some significance in both science and engineering applications.This paper introduces development history of SAW technology and current situation of the research. This paper elaborates the classification, characteristics and principle of passive wireless SAW sensors. Then the physical construction and testing principle of a passive wireless resonant SAW sensor and measurement system are analyzed.The pressure sensing principle of one-port SAW resonator is analyzed. After analyzing and comparing the performance of normal bracing structures in mechanics, we use a freely supported beam for sensing deforming structure. Based on the elastic mechanics theory, the maximum load of a freely supported beam and the strain distribution on both sides of the beam are analyzed. Two SAW one-port resonators with identical characteristics are arranged on the biggest strain area on both sides of the beam, and the position of the two resonators is centrosymmetrical. This differential measurement structure composed of two SAW resonators not only has a high pressure sensitivity but also can compensate the temperature drift.On the basis of the theoretical research on the passive wireless SAW pressure sensor and the design of the sensing unit, a design scheme of the sensor structure is presented, which includes designs of pressure transfer structure, dimension of sensing unit, correcting mechanism, fabrication of SAW device, encapsulation technology of sensor , leading wire and etc.In this paper, the strain distribution on sensing chip is simulated by the finite element analysis software ANSYS, and the performance of SAW pressure sensor and system is tested. The experimental results are compared with the theoretical calculation...