Finite element simulation of bulk- and surface acoustic wave (SAW) interaction in SAW devices

Abstract

Though loss parameters in SAW propagation are used as input for fast analysis models for the simulation of SAW devices, the quantitatively correct description of loss mechanisms is still a challenging task. Therefore, it is important to develop exact measurement and simulation methods which are able to determine these loss parameters accurately. By the use of special boundary conditions, the finite element method (FEM) is able to fulfill these requirements. Regarding the periodic substructure of common SAW devices, we have incorporated periodic boundary conditions (PBCs) in our simulation code. The piezoelectric substrate of SAW devices operating at high frequencies can be modeled as a semi-infinite half space. Therefore, we introduce newly evolved absorbing boundary conditions. They allow us to examine effects emerging from bulk acoustic wave (BAW) radiation (e.g. bulk wave onset frequencies) and assess propagation loss due to leakage and bulk wave conversion accurately.