Patent ID: 6759928
Filing Date: 2004-07-06
Classification: H03H

Abstract:
A surface acoustic wave device, comprising:first and second stages, which are cascade-connected, the first stage having a plurality of interdigital transducers of a first type disposed on a surface acoustic wave propagation path of a piezoelectric substrate, and the second stage having a plurality of interdigital transducers disposed on the surface acoustic wave propagation path, wherein the plurality of interdigital transducers of the second stage include interdigital transducers of the first type and Interdigital transducers of a second type, which are disposed alternately, wherein when an aperture length of an electrode finger of the interdigital transducers of the first type is denoted by X, each of the interdigital transducers of the second type has two divided interdigital transducers each having an electrode finger in which each aperture length is denoted by substantially X/2, and wherein the interdigital transducers of the first stage are connected to an unbalanced input or output terminal pair, and two divided interdigital transducers of the second type are serial-connected, and the electrodes of the respective electrode fingers are led from the two divided interdigital transducers, and are connected to a balanced output or input terminal pair, and the respective electrode fingers of the two divided interdigital transducers are disposed so that phases of signals in the balanced terminal pair are different at 180Â° , and wherein the interdigital transducers of the first type of the first and second stages are cascade-connected to each other in a plurality of connection parts of the interdigital transducers, and a phase of the interdigital transducers of the first type is reversed in each neighboring connection part of the plurality of connection parts.