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US 6,147,574 AGranted
Unidirectional surface acoustic wave transducer and transversal-type saw filter having the same
AssigneeMurata Manufacturing Co., Ltd.
InventorHideo Kidoh
Life of this patent
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Abstract
A unidirectional surface acoustic wave transducer includes a plurality of interdigital transducers and a plurality of reflectors disposed on a piezoelectric substrate. The directivity of a first group of the plurality of reflectors is opposite relative to the directivity of a second group of the plurality of reflectors.
Claims8
A unidirectional surface acoustic wave transducer, comprising:
- a piezoelectric substrate;
- a plurality of interdigital transducers disposed on the piezoelectric substrate;
- a plurality of reflectors disposed on the piezoelectric substrate;
- wherein the directivity of a first group of the plurality of reflectors is opposite to the directivity of a second group of the plurality of reflectors, and center positions of electrode fingers of the first group of the reflectors are shifted by about .lambda./8 in a first direction which is substantially perpendicular to the electrode fingers from a center position of electrode fingers of the interdigital transducers, where .lambda. represents a wavelength corresponding to a center frequency of a surface acoustic wave excited by the transducer, while center positions of electrode fingers of the second group of the reflectors are shifted by about .lambda./8 from the center position of electrode fingers of the interdigital transducers in a second direction which is opposite to the first direction.
1 more element
A transversal-type surface acoustic wave filter comprising:
- a surface acoustic wave substrate;
- an input-side unidirectional transducer provided on the surface acoustic wave substrate;
- and
- an output-side unidirectional transducer provided on the surface acoustic wave substrate in a direction in which a surface acoustic wave excited by the input-side unidirectional transducer propagates, the output-side unidirectional transducer including a plurality of interdigital transducers, a first reflector having a forward directivity and a second reflector having a reverse directivity;
- wherein each of the first reflector, the second reflector, and the plurality of interdigital transducers comprises a plurality of electrode fingers, and center positions of the electrode fingers of the first reflector are shifted by about .lambda./8 from center positions of the electrode fingers of the interdigital transducers toward a side where the input-side unidirectional transducer is provided, where .lambda. represents a wavelength corresponding to a center frequency of a surface acoustic wave excited by the transducer, while center positions of the electrode fingers of the second reflector are shifted by about .lambda./8 from the center position of the electrode fingers of the interdigital transducers toward a side where the input-side unidirectional transducer is not provided.
2 more elements
Dependencies are inferred from the claim text.