Patent ID: 6570470
Filing Date: 2003-05-27
Classification: H03H

Abstract:
A surface acoustic wave filter comprising:a series resonator group including a plurality of surface acoustic wave electrodes formed on a surface of a piezoelectric substrate and electrically disposed in series between an input terminal and an output terminal, and a parallel resonator group including a plurality of surface acoustic wave electrodes individually electrically disposed in parallel between an input- or output-terminal of the individual surface acoustic wave electrodes of the series resonator group and a ground electrode, wherein a resonant frequency formed by a part of surface acoustic wave electrodes among the surface acoustic wave electrodes of the parallel resonator group is lower than an antiresonant frequency formed by the other surface acoustic wave electrodes of the parallel resonator group and is higher than a resonant frequency formed by the other surface acoustic wave electrodes of the parallel resonator group, wherein the surface acoustic wave electrode comprises comb electrodes opposed to each other to have their electrode fingers interdigitated with each other, and wherein the other surface acoustic wave electrodes of the parallel resonator group have a greater ratio of the width to the pitch of the electrode finger than the part of the surface acoustic wave electrodes of the parallel resonator group.