Wave transmission lines and networks – Coupling networks – Electromechanical filter
Patent
1987-07-15
1989-10-31
LaRoche, Eugene R.
Wave transmission lines and networks
Coupling networks
Electromechanical filter
333193, 333153, 310313B, 310313D, H03H 364
Patent
active
048780367
ABSTRACT:
A surface elastic wave filter has a pair of electrodes on a surface of a piezoelectric body, and at least one of the electrodes is constructed as electrode fingers in the form of comb teeth which are progressively spread away from each other along a direction normal to the direction in which a surface elastic wave is propagated on the surface of the piezoelectric body. A grating or dot structure as a scattering reflector for scattering and reflecting a portion of the surface elastic wave is disposed in a desired position between the electrodes. Alternatively, some of electrode fingers of a surface elastic wave filter are dropped or removed, or divided voltages are applied to electrode fingers, or a scattering reflector is added to a filter with some of its electrode fingers removed or with divided voltages applied to electrode fingers. With such an arrangement, a filter having good selectivity and desired frequency characteristics can be achieved.
REFERENCES:
patent: 3946342 (1976-03-01), Hartmann
patent: 3999153 (1976-12-01), Borner
patent: 4055820 (1977-10-01), Solie
patent: 4130813 (1978-12-01), Sandy et al.
patent: 4134087 (1979-01-01), Gerard et al.
patent: 4155056 (1979-05-01), Cross
patent: 4336514 (1982-06-01), Paige
patent: 4635008 (1987-01-01), Solie
Kohda Toichi
Takeuchi Yoshihiko
Yatsuda Hiromi
Yoshikawa Shokichiro
Ham Seung
LaRoche Eugene R.
Nihon Musen Kabushiki Kaisha
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