Acoustic surface wave devices
First Claim
1. An acoustic surface wave resonator device comprising, a substrate having a surface layer of piezoelectric material, a pair of spaced apart reflectors on the piezoelectric surface forming a resonant cavity capable of supporting an acoustic surface standing wave at or near a predetermined frequency, and means for coupling with acoustic surface standing wave energy in the resonator, the coupling means including two similar arrays of parallel conductive strips on the piezoelectric surface transverse to the length of the cavity and located between the pair of reflectors, the strips of each array having a centre-to-centre spacing of half a wavelength or an odd integral multiple of half a wavelength of acoustic surface waves at said predetermined frequency, the spacing between the two arrays being a quarter wavelength or an odd integral multiple of a quarter wavelength of acoustic surface waves at said predetermined frequency, and a point mid-way between the two arrays being at the centre of the resonant cavity or displaced from the centre of the resonant cavity by half a wavelength or an integral multiple of a half wavelength of acoustic surface waves at said predetermined frequency.
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Accused Products
Abstract
An electrode structure within the cavity of an acoustic surface wave resonator, e.g. an interdigital transducer or a multistrip coupler, has two sections separated by an odd integral multiple of a quarter wavelength of the standing wave in the cavity and located with respect to the center of the cavity so that all the electrodes are midway between a node and an adjacent antinode of the standing wave. Distortion of the resonator response due to reflection by the electrodes of the transducer or coupler is suppressed by this arrangement.
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Citations
14 Claims
- 1. An acoustic surface wave resonator device comprising, a substrate having a surface layer of piezoelectric material, a pair of spaced apart reflectors on the piezoelectric surface forming a resonant cavity capable of supporting an acoustic surface standing wave at or near a predetermined frequency, and means for coupling with acoustic surface standing wave energy in the resonator, the coupling means including two similar arrays of parallel conductive strips on the piezoelectric surface transverse to the length of the cavity and located between the pair of reflectors, the strips of each array having a centre-to-centre spacing of half a wavelength or an odd integral multiple of half a wavelength of acoustic surface waves at said predetermined frequency, the spacing between the two arrays being a quarter wavelength or an odd integral multiple of a quarter wavelength of acoustic surface waves at said predetermined frequency, and a point mid-way between the two arrays being at the centre of the resonant cavity or displaced from the centre of the resonant cavity by half a wavelength or an integral multiple of a half wavelength of acoustic surface waves at said predetermined frequency.
- 9. A multi-resonator device comprising first and second acoustic surface wave resonator devices coupled together so as to transfer energy between the first and the second resonator devices, each of said resonator devices comprising, a substrate of piezoelectric material, a pair of aligned spaced apart reflectors coupled to the surface of the substrate and comprising an array of discrete parallel strips arranged to form a resonant cavity able to support an acoustic surface standing wave in the substrate at a predetermined frequency, and means including two similar arrays of parallel conductive strips arranged on the substrate transverse to the length of the cavity and located between the pair of reflectors for coupling with the acoustic standing wave energy in the substrate, the strips of each array having a center-to-center spacing of a half wavelength or an odd integral multiple thereof at said predetermined frequency, the two arrays being spaced apart a quarter wavelength or an odd integral multiple thereof at said predetermined frequency, a midpoint between the two arrays being located at the center of the resonant cavity or displaced therefrom by a half wavelength or an integral multiple thereof at said predetermined frequency.
Specification