Consistent generalization of COM equations to three-dimensional structures and the theory of the SAW transversely coupled waveguide resonator filter

An analytical theory for calculating the response of a transversely coupled waveguide resonator filter (TCF) is derived consistently from the analytical model for the description of two-dimensional structures. The COM equations for slowly varying amplitudes of the SAW electric potential as functions of the longitudinal coordinate are derived. The coefficients of these equations such as reflectivity, phase delay and transduction coefficient are calculated for each mode. The theory connects the material and geometrical parameters of the structure with the characteristics of the TCF. The frequency dependence of the admittance matrix and insertion loss for one and two cascaded filters are considered. The splitting of the resonance peaks due to cascading is investigated. Good agreement between theoretical and experimental results is found.>