A general Green function analysis for SAW devices

Methods for calculating Green functions that can fully characterize the properties of a SAW substrate with respect to both mechanical and electrical excitation are described. The Green function is initially represented as a 4×4 matrix of functions in k (wavenumber) space; it describes the three surface displacement components and the electrical potential in terms of the three surface stress components and the surface charge density (line sources are assumed). The x space representation of the Green function is computed by a Fourier transform when required. The software includes facilities for locating and characterizing all singular points. The Green function method has been applied to the analysis of wave propagation in periodic structures including both electrical and mass loading effects; a simple normal mode model is used to describe the mechanical behaviour of the electrodes. Examples of practical analyses are given; data is also given on the convergence of the method with respect to the numbers of sample points