Analysis of SAW filter fabricated on anisotropic substrate using finite-difference time-domain method

The finite-difference time-domain (FDTD) method is extended to analyze surface acoustic wave (SAW) filter fabricated on an anisotropic substrate. In this method, the partial derivatives of quasi-static Maxwell´s equations and equation of motion are discretized to centered finite-differences. The spatial layout of the field components of this study differs from that of the isotropic case. The current two-dimensional spatial layout needs two components on particle velocity and electrical field nodes, three components on a stress node, in contrast to the isotropic case which requires one component on a particle velocity node, and one or two components on a stress node. Furthermore, the perfectly matched layer (PML) boundary condition is applied to reduce the spurious reflections. The proposed method is used to analyze the frequency response of a SAW filter fabricated on a Y-Z lithium tantalate (LiTaO₃) substrate.