US 12,334,908 B2
Bulk acoustic wave filters for improving noise factor
Koichi Hatano, Yokohama (JP)
Assigned to SKYWORKS SOLUTIONS, INC., Irvine, CA (US)
Filed by SKYWORKS SOLUTIONS, INC., Irvine, CA (US)
Filed on Nov. 29, 2022, as Appl. No. 18/059,520.
Claims priority of provisional application 63/288,326, filed on Dec. 10, 2021.
Prior Publication US 2023/0188115 A1, Jun. 15, 2023
Int. Cl. H03H 9/60 (2006.01); H03H 9/13 (2006.01); H03H 9/58 (2006.01); H03H 9/74 (2006.01)
CPC H03H 9/605 (2013.01) [H03H 9/133 (2013.01); H03H 9/587 (2013.01); H03H 9/74 (2013.01)] 16 Claims
OG exemplary drawing
 
1. 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.