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Abstract

A surface elastic wave filter for processing a supplied signal into a signal with nonlinear-phase frequency characteristics has a piezoelectric substrate for propagating a surface elastic wave through a surface layer thereof and spaced input and output electrodes disposed on the surface layer for sending and receiving the surface elastic wave. Each of the input and output electrodes has a pair of common electrodes having comb-shaped interdigitating electrode fingers extending therebetween. The central electrode fingers of the input and output electrodes have central axes across the direction of propagation of the surface elastic wave. The distance along the direction of propagation between the central axes is varied in the direction substantially normal to the direction of propagation. The surface elastic wave filter may include an electric conductor disposed on the piezoelectric substrate between the input and output electrodes and having a dimension in the direction of propagation, the dimension being varied in the direction substantially normal to the direction of propagation. A medium for varying the speed of propagation of the surface elastic wave may be positioned in place of the electric conductor.

First Claim