US 5,963,114 AGranted

Surface-acoustic-wave device having an improved pass-band characteristic and an improved degree of freedom for setting input and output impedances

AssigneeFujitsu Limited

InventorsMasanori Ueda, Gou Endoh, Osamu Kawachi, Yoshiro Fujiwara

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Abstract

A surface-acoustic-wave device includes at least first and second surface-acoustic-wave elements formed on a common piezoelectric substrate and cascaded with each other, each of the first and second surface-acoustic-wave elements including a plurality of interdigital electrodes having a plurality of electrode fingers overlapping with each other in correspondence to a path of a surface acoustic wave on the piezoelectric substrate, wherein the width of overlapping of the electrode fingers is changed between the first surface-acoustic-wave element and the second surface-acoustic-wave element.

Claims7

Dependent claims

A surface-acoustic-wave device, comprising:

a piezoelectric substrate;
at least first and second surface-acoustic-wave elements formed commonly on said piezoelectric substrate each a predetermined propagation path of a surface acoustic wave on said piezoelectric substrate;
each of said first and second surface-acoustic-wave elements including a plurality of interdigital electrodes disposed along said predetermined propagation path of said surface acoustic wave;
each of said plurality of interdigital electrodes including a primary-side electrode having a plurality of mutually parallel electrode fingers extending in a first direction across said propagation path and a secondary-side electrode having a plurality of mutually parallel electrode fingers extending in a second direction opposite to said first direction across said propagation path;
said electrode fingers of said primary-side electrode and said electrode fingers of said secondary-side electrode being disposed, in each of said interdigital electrodes in each of said first and second surface-acoustic-wave elements, alternately along said propagation path so as to overlap with a predetermined overlap width when viewed in a direction of said propagating path;
said overlap width having a first value commonly in said plurality of interdigital electrodes forming said first surface-acoustic-wave element and a second, different value commonly in said plurality of interdigital electrodes forming said second surface-acoustic-wave element;
and
said first surface-acoustic-wave element being cascaded to said second surface-acoustic-wave element by connecting a secondary-side electrode of an interdigital electrode included in said first surface-acoustic-wave element to a primary-side electrode of an interdigital electrode included in said second surface-acoustic-wave element, wherein
each of said first and second surface-acoustic-wave elements is a surface-acoustic-wave device of a double-mode type and includes first and second reflectors formed on a surface of said piezoelectric substrate, said first and second reflectors thereby defining said propagating path of said surface acoustic wave, each of said first and second surface-acoustic-wave elements further including first, second and third interdigital electrodes disposed between said first and second reflectors consecutively from said first reflector to said second reflector as said plurality of interdigital electrodes.

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Dependencies are inferred from the claim text.

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Abstract

A surface-acoustic-wave device, comprising:

a piezoelectric substrate;
at least first and second surface-acoustic-wave elements formed commonly on said piezoelectric substrate each a predetermined propagation path of a surface acoustic wave on said piezoelectric substrate;
each of said first and second surface-acoustic-wave elements including a plurality of interdigital electrodes disposed along said predetermined propagation path of said surface acoustic wave;
each of said plurality of interdigital electrodes including a primary-side electrode having a plurality of mutually parallel electrode fingers extending in a first direction across said propagation path and a secondary-side electrode having a plurality of mutually parallel electrode fingers extending in a second direction opposite to said first direction across said propagation path;
said electrode fingers of said primary-side electrode and said electrode fingers of said secondary-side electrode being disposed, in each of said interdigital electrodes in each of said first and second surface-acoustic-wave elements, alternately along said propagation path so as to overlap with a predetermined overlap width when viewed in a direction of said propagating path;
said overlap width having a first value commonly in said plurality of interdigital electrodes forming said first surface-acoustic-wave element and a second, different value commonly in said plurality of interdigital electrodes forming said second surface-acoustic-wave element;
and
said first surface-acoustic-wave element being cascaded to said second surface-acoustic-wave element by connecting a secondary-side electrode of an interdigital electrode included in said first surface-acoustic-wave element to a primary-side electrode of an interdigital electrode included in said second surface-acoustic-wave element, wherein
each of said first and second surface-acoustic-wave elements is a surface-acoustic-wave device of a double-mode type and includes first and second reflectors formed on a surface of said piezoelectric substrate, said first and second reflectors thereby defining said propagating path of said surface acoustic wave, each of said first and second surface-acoustic-wave elements further including first, second and third interdigital electrodes disposed between said first and second reflectors consecutively from said first reflector to said second reflector as said plurality of interdigital electrodes.

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