Surface acoustic wave device having apodized transducer provided with irregular pitch electrode group
AssigneeHitachi, Ltd.
InventorsTakashi Shiba, Yuji Fujita, Toshimitsu Takahashi, Jun Yamada
Life of this patent
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Abstract
A surface acoustic wave device characterized in that in addition to linear first bus-bar electrodes which connect in alignment the edges of the same potential electrodes of interdigital electrodes, second bus-bar electrodes are provided which connect the same potential electrodes in the vicinity of the overlapping positions. Also disclosed is a surface acoustic wave device characterized in that the metalized ratio g/p, which is the ratio of the width of an electrode and the intercentral distance between the adjacent electrodes in an irregular pitch electrode group, is varied between 0.1 to 0.4 or between 0.6 to 0.9.
Claims8
A surface acoustic wave device comprising:
- a piezoelectric substrate;
- an input transducer comprised of interdigital electrodes and formed on said substrate;
- and
- an output interdigital transducer comprised of interdigital electrodes and formed on said substrate;
- at least one of said input transducer and said output transducer being comprised of:
- first bus-bar electrodes which connect the edges of the same potential electrodes of said interdigital electrodes in alignment;
- second bus-bar electrodes which connect the same potential electrodes of said interdigital electrodes in the vicinity of the overlapping portions;
- a first electrode group comprised of a plurality of electrodes having the same width disposed between said first bus-bar electrodes and said second bus-bar electrodes at a regular pitch having an interval equal to the width of said electrodes;
- and
- a second electrode group comprised of electrodes arranged at irregular pitches with one end thereof connected to one of said second bus-bar electrodes, and the other ends of at least a part of said electrodes being overlapped with the different potential electrodes, thereby constituting sources of a surface acoustic wave.
A surface acoustic wave device comprising:
- a piezoelectric substrate;
- an input transducer comprised of interdigital electrodes and formed on said substrate;
- and
- an output interdigital transducer comprised of interdigital electrodes and formed on said substrate;
- at least one of said input transducer and said output transducer being comprised of:
- bus-bar electrodes which connect the edges of the same potential electrodes of said interdigital electrodes in alignment;
- an irregular pitch electrode group comprised of electrodes arranged at irregular pitches with one end thereof connected to one of said bus-bar electrodes, and the other ends of at least a part of said electrodes being overlapped with the different potential electrodes, thereby constituting the sources of a surface acoustic wave, each of adjacent electrodes which have the same width and the same length forming a pair, the metalized ratio g/p, which is which is the ratio of the width g of said electrode and the intercentral distance p between the adjacent electrodes, being varied in the range of 0.1 .ltoreq.g/p.ltoreq.0.4 or 0.6.ltoreq.g/p<0.9 depending upon said pair, thereby suppressing the undesired reflection produced at the boundary of said electrode.
Dependencies are inferred from the claim text.