A DISCRETE ONE-COMPONENT WAVE MODEL AND ITS APPLICATION TO SAW RESONATOR FILTERS

A one component acoustic bulk wave model is presented for the descript ion of SAW devices using plane waves or waveguide modes. No equivalent circuit components are used, and the calculations always remain on th e level of acoustic waves. As fundamental elements the transfer matrix and the source vector of one electrode region are derived. Using thes e elements, the particle displacements in an array consisting of strip like electrodes can be calculated as a function of all single capacito r voltages taking into account the boundary conditions including the a mplitudes of foreign waves meeting the array. After determining the wa veguide mode velocities and profiles the model is applied to transvers ely coupled waveguide resonator filters resulting in the admittance ma trix which is needed to calculate the filter insertion loss. Two filte r examples are investigated, and a sufficiently good agreement of the theoretical and experimental results is found. The resonance splitting due to cascading of two (or more) single resonator filters can be inc reased by a coupling inductor yielding a smaller insertion loss under matched conditions at a given bandwidth.