Precise Sensitivity Calculation Method of SAW-Based Pressure Sensor

In this work, we propose a precise sensitivity calculation method for a surface acoustic wave (SAW)-based pressure sensor. The Tiersten–Sinha perturbation theory and finite-element method (FEM) were used to analyze the mechanical properties of a diaphragm based on piezoelectric material and achieved the pressure sensitivity distribution. Many factors affecting the pressure sensitivity could be taken into consideration by this method, including the material, the dimension of the diaphragm, as well as the position of electrodes. To prove the theoretical prediction, SAW pressure-sensing devices in ST and AT quartz diaphragm at two different thicknesses are prepared, and electrodes are patterned at different positions on the surface defined as type I and type II. Measured results confirmed the excellent consistency between theoretical and experimental results. For the group of 0.45-mm diaphragm, comparing the theoretical and the experimental results, errors of the type I and type II ST quartz sensors are 3.92% and 2.63%, and the error of the type I AT quartz sensor is only 0.96%. For the group of 0.3-mm diaphragm, errors of type I ST and AT quartz are 6.3% and 1.6%, respectively.