Surface acoustic wave filter

Details Surface acoustic wave filter Surface acoustic wave filter

2005-12-06

2005-12-06

Summons, Barbara (Department: 2817)

Wave transmission lines and networks

Coupling networks

Electromechanical filter

C310S31300R

Reexamination Certificate

active

06972643

ABSTRACT:
A longitudinally coupled surface acoustic wave filter includes a first, second and third IDT electrodes and a first and second reflector electrodes on a piezoelectric substrate. The IDT electrodes each include a primary excitation region having λ/2 electrode finger pitches, where λ is the wavelength of a surface acoustic wave. The primary excitation region is phase-shifted by a certain amount in accordance with a desired passband frequency response. The IDT electrodes further include a plurality of secondary excitation regions each having electrode finger pitches different from the λ/2 pitches. All of the electrode finger pitches of the surface acoustic wave filter thus range from 0.8λ/2 to 1.2λ/2, so that a loss increase caused by discontinuity between the IDT electrodes is prevented.

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International Search Report corresponding to application No. PCT/JP02/06434 dated Oct. 8, 2002.
English translation of Form PCT/ISA/210, dated Oct. 8, 2002.

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