The theory of the SAW transversely coupled waveguide resonator filter

The known theory of coupling-of-modes (COM) equations for description of two-dimensional structures is generalized consistently to the three-dimensional structure of transversely coupled waveguide resonator filter (TCF). The COM equations for slowly varying amplitudes of SAW electric potential as function of longitudinal coordinate are derived taking into account all the possible modes. The theory connects the material and geometrical parameters of the structure with the characteristics of TCF. The frequency dependence of admittance matrix and insertion loss for one and two cascaded filters are considered. The splitting of the resonance peaks due to cascading is investigated. A good coincidence between theoretical and experimental results is found