Acoustic surface wave device
AssigneeFujitsu Limited
InventorsMasaaki Ono, Noboru Wakatsuki
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Abstract
An acoustic surface wave device comprising: a piezoelectric substrate; a pair of input and output transducers located diagonally from each other; and a multistrip coupler between the two transducers. In this device, the spacing of electrodes of at least one of the transducers is 3.lambda./4 (.lambda.: wavelength of the acoustic surface waves) and, accordingly, the resulting spurious frequency response is excluded by using the transfer characteristics of the multistrip coupler.
Claims7
An acoustic surface wave device comprising:
- a piezoelectric substrate having a planer surface for propagation of acoustic surface waves;
- an input transducer formed on the surface of said substrate, for converting electrical energy into said acoustic surface waves;
- an output transducer formed on the surface of said substrate and located diagonally with respect to said input transducer, for converting said acoustic surface waves into electrical energy, at least one of said input and output transducers having electrodes whose spacing is about 3.lambda./4 where .lambda. is the wavelength of said acoustic surface waves;
- and
- a multistrip coupler including a plurality of parallel and equally spaced conductors, formed on the surface of said substrate and interposed between said input and output transducers so as to be substantially orthogonal to the propagation direction of said acoustic surface waves, the number and spacing of said conductors being selected to reduce the transfer of undesired acoustic surface waves which are in the vicinity of the frequency f.sub.o /3 where f.sub.o is the frequency of said acoustic surface waves.
An improved acoustic wave device of the type which generates a desired response at a frequency f.sub.o by using a piezoelectric substrate, input and output transducer means mounted on the substrate at spaced-apart positions, and wave directing means mounted on the substrate for directing acoustic surface waves generated by the input transducer means toward the output transducer means, said transducer means having a tendency to produce a spurious response at a frequency other than f.sub.o, wherein the improvement comprises:
- one of said input and output transducer means comprises means for substantially limiting the frequency of the spurious response produced to a fractional value of f.sub.o ;
- and
- the wave directing means comprises means for attenuating the spurious response at the fractional value of f.sub.o more than the desired response at f.sub.o.
Dependencies are inferred from the claim text.