A derivation of the coupling-of-modes parameters based on the scattering analysis of SAW transducers and gratings

Using the analytic theory of S. Datta and B.J. Hunsinger (1980) for the scattering of SAWs by an electrode in a periodic array and interpreting these results slightly differently than C.M. Panasik and B.J. Hunsinger (1981), a more consistent and satisfying result is obtained for the scattering matrix representation of SAW transducers. By comparing these results with equivalent solutions obtained using the coupling of modes (COM) method, the COM parameters for transducers and gratings with periodic and regular electrodes are derived. This method allows all relevant COM parameters to be obtained in a mutually consistent manner. The consistency with which these parameters are derived allows for the straightforward modeling and explanation of devices such as the NSPUDT whose unidirectional behavior results from the exploitation of the phase differences between the SAW potential and the accompanying mechanical displacements