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US 12,334,908 B2Granted
Bulk acoustic wave filters for improving noise factor
AssigneeSkyworks Solutions, Inc.
InventorKoichi Hatano
Life of this patent
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Abstract
A ladder type acoustic wave filter is disclosed. The acoustic wave filter can include a plurality of parallel arm resonators and a plurality of series arm resonators, in which an electromechanical coupling coefficient of a parallel arm resonator closest to an input node of the acoustic wave filter among the plurality of parallel arm resonators can be smaller than an electromechanical coupling coefficient of a series arm resonator closest to the input node among the plurality of series arm resonators.
Claims16
A ladder type acoustic wave filter, the acoustic wave filter comprising:
- a plurality of parallel arm resonators;
- and
- a plurality of series arm resonators, an electromechanical coupling coefficient of a parallel arm resonator closest to an input node of the acoustic wave filter among the plurality of parallel arm resonators being smaller than an electromechanical coupling coefficient of a series arm resonator closest to the input node of the acoustic wave filter among the plurality of series arm resonators, the plurality of parallel arm resonators and the plurality of series arm resonators being formed from film bulk acoustic wave resonators, each of the film bulk acoustic wave resonators including a substrate, a piezoelectric film supported over the substrate and over a cavity defined between the piezoelectric film and the substrate, and an electrode layer disposed on a surface of the piezoelectric film, the film bulk acoustic wave resonator of the parallel arm resonator closest to the input node including a first low propagation velocity region extending along a periphery of an active region of the piezoelectric film that can oscillate, and the film bulk acoustic wave resonator of the series arm resonator closest to the input node including a second low propagation velocity region extending along a periphery of an active region of the piezoelectric film that can oscillate, a width of the first low propagation velocity region being greater than a width of the second low propagation velocity region.
A wireless communication device comprising:
- an antenna;
- and
- a multiplexer coupled to the antenna, the multiplexer including a plurality of filters coupled to a common node and arranged to filter a radio frequency signal, at least one of the plurality of filters including a plurality of parallel arm resonators, and a plurality of series arm resonators, an electromechanical coupling coefficient of a parallel arm resonator closest to an input node of the at least one of the plurality of filters among the plurality of parallel arm resonators being smaller than an electromechanical coupling coefficient of a series arm resonator closest to the input node of the at least one of the plurality of filters among the plurality of series arm resonators, the plurality of parallel arm resonators and the plurality of series arm resonators being formed from film bulk acoustic wave resonators, each of the film bulk acoustic wave resonators including a substrate, a piezoelectric film supported over the substrate and over a cavity defined between the piezoelectric film and the substrate, and an electrode layer disposed on a surface of the piezoelectric film, the film bulk acoustic wave resonator of the parallel arm resonator closest to the input node including a first low propagation velocity region extending along a periphery of an active region of the piezoelectric film that can oscillate, and the film bulk acoustic wave resonator of the series arm resonator closest to the input node including a second low propagation velocity region extending along a periphery of an active region of the piezoelectric film that can oscillate, a width of the first low propagation velocity region being greater than a width of the second low propagation velocity region.
Dependencies are inferred from the claim text.