Wave transmission lines and networks – Coupling networks – Electromechanical filter
Patent
1998-02-24
2000-10-24
Pascal, Robert
Wave transmission lines and networks
Coupling networks
Electromechanical filter
333195, 310313D, H03H 964
Patent
active
06137380&
ABSTRACT:
A surface acoustic wave filter significantly improves attenuation in the stopband by using a spurious component to improve the filter characteristics. The filter includes a surface acoustic wave substrate and a series resonator having a resonant frequency and an antiresonant frequency. The series resonator is electrically disposed between an input terminal and an output terminal in series so as to define a series arm. The filter also includes at least one parallel resonator having a resonant frequency and an antiresonant frequency which is substantially identical to the resonant frequency of the series resonator. The at least one parallel resonator is electrically disposed between the series arm and a ground terminal so as to define a first parallel arm. The series arm and the parallel arm define a ladder circuit such that the surface acoustic wave filter has a predetermined pass band. The first parallel resonator has a spurious component at a frequency located between the resonant frequency of the first parallel resonator and a low end of the passband of the surface acoustic wave filter or at a frequency located between the antiresonant frequency of the series resonator and a high end of the passband of the surface acoustic wave filter.
REFERENCES:
patent: 4635009 (1987-01-01), Ebata
patent: 5459368 (1995-10-01), Onishi et al.
patent: 5631515 (1997-05-01), Mineyoshi et al.
patent: 5666092 (1997-09-01), Yamamoto et al.
patent: 5729186 (1998-03-01), Seki et al.
patent: 5831493 (1998-11-01), Ushiroku
Taniguchi Norio
Ushiroku Tadamasa
Murata Manufacturing Co. Ltd
Pascal Robert
Summons Barbara
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