Extension of scalar potential formalism for transverse mode analysis of surface acoustic wave resonators

This paper describes extension of the scalar potential (SP) theory for the analysis of surface acoustic wave (SAW) devices. First, it is shown that the SP theory is equivalent to the two-dimensional wave equation for a shear-vertical bulk wave, where variation of acoustic properties is expressed as that of the mass density while the elastic properties are uniform in the structure. When periodic variation of the mass density and stress sources is taken into account, the theory is compatible to the coupling-of-mode (COM) model. The compatibility allows us to derive primary parameters necessary for the analysis from those determined for the COM model. The theory is applied to the analysis of a SAW resonator on the 15°YX-LiNbO₃ substrate, and effectiveness of the present method is demonstrated.