Study of loss mechanisms in temperature compensated surface acoustic wave devices based on finite element method analysis using hierarchical cascading technique

Abstract

This paper discusses loss mechanisms of temperature compensated surface acoustic wave (TC-SAW) devices using the SiO2 overcoated 128°YX-LiNbO3 (128-LN) substrate. Analysis is based on the finite element method (FEM) combined with the hierarchical cascading technique and the general purpose graphics processing unit. Three kinds of FEM model, i.e. 2.5D, three dimensional (3D) periodic and full 3D are analyzed without taking additional losses, i.e. material viscous loss, dielectric loss and electrode ohmic loss, and influence of scattering at structural discontinuities is evaluated solely. It is shown that although Q reduction is significant with an increase of the simulation dimension, in other words, that of the number of acoustic scattering mechanisms, estimated Q value is still considerably higher than reported values even for full 3D simulation. This result indicates that acoustic scattering at structural discontinuities is not a dominant loss mechanism in current TC-SAW devices employing the SiO2 overcoated 128-LN substrate.