DERIVATION OF COM EQUATIONS USING THE SURFACE IMPEDANCE METHOD

The surface impedance method is used for the consistent derivation of coupling of modes equations which describe the interaction of SAW with a periodical system of electrodes of finite thickness, The exact anal ytic solution of the electrostatic problem in the presence of an arbit rary external electric field for a plane system of electrodes is appli ed to the calculation of the charge and electric field distributions, Mechanical perturbations are taken into account to first order of the thickness of the electrodes, As a result the scalar self-consistent eq uation for the electric potential of acoustic waves in the gratings is obtained, For the periodic structure this equation is reduced to the form of COM equations for slowly varying amplitudes, Analytical expres sions for all coefficients of the COM equations connecting them with g eometrical and material parameters are found. The NSPUDT effect can be considered, Dissipation and energy storage terms can be introduced em pirically, The solution of the COM equations is represented in the for m of a P matrix with elements written in a convenient form, A simple f ormula for calculating the location of maximum transducer frequency re sponse is proposed, The balance of energy is considered, Some new rela tions among the elements of P matrix are found.