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US 5,689,220 AGranted
Laterally coupled piezoelectric resonator ladder-type filter with at least one width expansion mode resonator
AssigneeMurata Manufacturing Co., Ltd.
InventorHiroaki Kaida
Life of this patent
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Abstract
A ladder-type filter having a circuit structure obtained by connecting a plurality of series resonators and a plurality of parallel resonators with each other. At least two plate-type resonators are laterally coupled with each other with respect to a mounting surface. At least one of the series and parallel resonators is an energy trap type piezo-resonator having a plate type piezoelectric vibrating part, a support part which is coupled to the piezoelectric vibrating part, and a holding part which is coupled to the support part.
Claims14
A ladder-type filter comprising:
- at least one series resonator forming a series arm and at least one parallel resonator forming a parallel arm,
- at least two of said series and parallel resonators being laterally coupled with each other with respect to a mounting surface,
- at least one of said series and parallel resonators including a substantially rectangular plate type piezoelectric vibrator having a ratio b/a being set in a range of +/-10% from the following value:
- b/a=n(-1.47.sigma.+1.88)
- wherein a and b respectively represent lengths of shorter and longer sides of said piezoelectric vibrator, .sigma. represents the Poisson's ratio of the material forming said piezoelectric vibrator and n represents an integer.
2 more elements
Dependencies are inferred from the claim text.