Piezoelectric resonant filter and duplexer

Details Piezoelectric resonant filter and duplexer Piezoelectric resonant filter and duplexer

2006-01-24

2006-01-24

Summons, Barbara (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S189000

Reexamination Certificate

active

06989723

ABSTRACT:
A piezoelectric resonant filter includes a group of series resonators and a group of parallel resonators for forming a ladder-type filter circuit. Each of the resonators has a piezoelectric thin film having piezoelectric characteristic, and lower and upper electrodes disposed on opposite surfaces of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film. The group of the parallel resonators exhibits a low frequency side attenuation extremum in the filter whereas the group of the series resonators exhibits a high frequency side attenuation extremum in the filter. At least one of the group of the series resonators and the group of the parallel resonators has a temperature compensating layer for bringing the temperature coefficient of the resonant frequency close to zero.

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