Simplified Model for FEM Simulation of SAW Delay Line Sensor

Abstract

Surface acoustic wave (SAW) devices can be modeled using various methods such as equivalent circuit model, coupling of modes method and finite element method (FEM). FEM simulation of SAW devices serves to optimize SAW structures and allows getting insight physics of propagation of SAW over the substrate. In most of the earlier work on FEM simulation of SAW sensors, entire device structure is considered for the simulation and the number of degrees of freedom (DOF) to solve is significantly high. Thus it is important to identify valid approximation and simplified models to reduce the computational cost. In this paper a 2D-finite FEM simulation of SAW delay line model using COMSOL Multiphysics (commercial FEM software) is discussed. We have modeled a Rayleigh wave type SAW device choosing YZ Lithium Niobate as the substrate. The major contribution of this work is the application of periodic boundaries to the transmitter interdigital transducer (IDT) to reduce the number of degrees of freedom of a SAW delay line model solution. The simulation methodology and time domain response of the model are discussed.