Spatial uniformity and broadband matching in multiply tapped SAW convolvers

A lossy transmission line model for the output plate of a SAW convolver used to process long-duration waveforms is used to derive an equivalent circuit that allows the spatial weighting functions or plate uniformity functions for either singly tapped or multiply tapped convolver geometries to be obtained. It is shown how this equivalent circuit can be used to calculate the output circuit loss under full overlap conditions. The equivalent circuit for the convolver, which includes the ac source terms due to the surface waves, is used for each intertap section of the convolver output plate waveguide. A circuit for the multiply tapped structure is assembled and analyzed using a frequency-domain circuit analysis program performance characteristics are obtained and used to illustrate the role of transmission line effects on the spatial uniformity for typical convolver configurations. Typical results of the computer-aided design of appropriate matching networks for an eleven-tap structure are given.