A powerful novel method for the simulation of waveguiding in SAW devices

A new method to simulate waveguiding in SAW filters is presented and applied to mobile communication and consumer electronics filters. It is based on the P-matrix method and discretizes the filter into longitudinal and transversal sections. Diffraction effects are introduced by considering free waveguide propagation within the longitudinal sections. This method is an extension of the pseudoinverse diffraction matrix method by Rooth et al. In contrast to the transmission matrix form of that scheme the presented method uses an intrinsically reciprocal 2D scattering matrix description. It is shown that the dispersion relations of the method are equivalent to those obtained by a 2D COM approach and hence both methods are equivalent. The scheme has proved to predict 2D effects in a wide range of filter types reliably. This is exemplified for recursive filters, as well as filters with apodized and fan-type IDTs built on quartz and lithium niobate. In order to better understand the filter behaviour visualizations of the wavefields are presented.