Love波传感器结构的有限元分析方法

Finite element method analysis of love wave sensors device

提出一种ANSYS分析Love波传感器性能的有限元方法。根据Love波传感器的特点,施加一维近似假设和周期性边界条件建立了由压电基片,金属电极和波导层组成Love波传感器的三维有限元分析模型,并在此模型分析结果基础上提取结构的特征频率。一方面运用开路和短路条件下的特征频率来计算机电耦合系数,另一方面结合微扰理论的计算得到器件的质量灵敏度。最后通过这两个参数来选取波导层厚度,使器件达到最优的性能。在不同的波导层厚度情况下,计算了SiO_2/ST-90°X石英和SiO_2/36°Y-X LiTaO_3两种结构Love波传感器结构的仿真结果,得到了这两种结构的波导层最优的厚度分别为0.11λ和0.2λ。与已报道的文献和实验的结果对比,本文所采用的方法明显优于传统的均匀层状结构理论分析的结果,通过仿真不同结构和材料参数的器件性能,有效地指导Love波传感器的设计。

A finite element method based on ANSYS is proposed to analyze love wave sensors. Firstly, with one dimensional approximation hypothesis and periodic boundary condition, a three dimensional finite element model of love wave sensor is developed, which is composed of substrate, electrode and guiding layer. The eigen frequencies can be extracted by the FEM anlysis. Then, the electromechanical coupling factor is calculated by the eigen frequencies of open and short circuit conditions while mass sensitivity is calculated based on perturbation theory. In the end, the optimum layer thickness is determined by the two parameters. With the variation of guiding layer thickness, the results of both SiO2/ST-90°X cut quartz and SiO2/36~Y-X LiTaO3 devices are presented. The optimum layer thickness is about 0.11 A and 0.2 A respectively. The simulation results are compared with the reported experimental result. It is obvious that the approach in this paper is better than conventional multi-layered method which omitted the electrodes＇ effect. The proposed approach is expected to provide effective guidance for love wave sensors design.