Analysis and design of low-loss SAW devices with internal reflections using coupling-of-modes theory

The analysis and design of a new family of SAW (surface acoustic wave) devices which take advantage of distributed internal reflections are discussed. It is noted that the deliberate inclusion of reflections makes many new devices possible. Among these are new low-loss filter structures, resonators and notch elements. However, the inclusion of internal reflections significantly complicates the analysis of these devices. Therefore, a very general coupling-of-modes (COM) model has been developed. The analysis is applicable to propagation on arbitrary crystal orientations, and both resistive and propagation losses are included in the model. Fundamental device parameters are derived in closed form from the COM equations. Several examples are given of some innovative structures, with theoretical and experimental results