Band rejection filter
AssigneeMurata Manufacturing Co., Ltd.
InventorsNorihiko NAKAHASHI, Yasumasa TANIGUCHI
Life of this patent
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Abstract
An inexpensive compact band rejection filter realizes a high sharpness of a filter characteristic at ends of passbands and has a large attenuation. In the band rejection filter, at least one of a plurality of elastic wave resonators, which contributes to formation of a transition band, has a propagation angle larger than those of the other elastic wave resonators. Accordingly, the at least one of the plurality of elastic wave resonators which contributes to the formation of the transition band has an electromechanical coupling coefficient that is smaller than electromechanical coupling coefficients of the other elastic wave resonators.
Claims22
A band rejection filter comprising:
- a ladder circuit including:
- a series arm arranged to connect an input terminal and an output terminal to each other;
- a parallel arm which is connected between the series arm and a ground potential;
- a plurality of elastic wave resonators which are disposed in at least one of the series arm and the parallel arm;
- and
- an inductance element which is disposed in at least one of the series arm and the parallel arm;
- and
- a first attenuation band, a first passband which is adjacent to the first attenuation band, a second attenuation band which is included in the first passband, and a transition band which is adjacent to the second attenuation band;
- wherein
- at least one of the elastic wave resonators which contributes to formation of the transition band has a propagation angle larger than propagation angles of the others of the elastic wave resonators.
A band rejection filter comprising:
- a ladder circuit including:
- a series arm arranged to connect an input terminal and an output terminal to each other;
- a parallel arm which is connected between the series arm and a ground potential;
- a plurality of elastic wave resonators which are disposed in at least one of the series arm and the parallel arm;
- and
- an inductance element which is disposed in at least one of the series arm and the parallel arm;
- and
- a first attenuation band, a first passband which is adjacent to the first attenuation band, a second attenuation band which is included in the first passband, and a transition band which is adjacent to the second attenuation band;
- wherein
- at least one of the elastic wave resonators which contributes to formation of the transition band has a propagation angle larger than propagation angle of the others of the elastic wave resonators, and therefore, the at least one of the elastic wave resonators which contributes to the formation of the transition band has an electromechanical coupling coefficient smaller than electromechanical coupling coefficients of the others of the elastic wave resonators.
Dependencies are inferred from the claim text.