US 12,244,300 B2
Ladder-type filter and multiplexer
Sho Iwasaki, Tokyo (JP); and Hitoshi Tsukidate, Tokyo (JP)
Assigned to TAIYO YUDEN CO., LTD., Tokyo (JP)
Filed by TAIYO YUDEN CO., LTD., Tokyo (JP)
Filed on Apr. 18, 2022, as Appl. No. 17/723,320.
Claims priority of application No. 2021-083401 (JP), filed on May 17, 2021; and application No. 2021-086702 (JP), filed on May 24, 2021.
Prior Publication US 2022/0368313 A1, Nov. 17, 2022
Int. Cl. H03H 9/60 (2006.01); H03H 9/13 (2006.01); H03H 9/205 (2006.01); H03H 9/70 (2006.01)
CPC H03H 9/605 (2013.01) [H03H 9/13 (2013.01); H03H 9/205 (2013.01); H03H 9/70 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A ladder-type filter comprising:
a support substrate;
a piezoelectric layer provided on the support substrate;
one or more parallel resonators each including a plurality of first electrode fingers provided on the piezoelectric layer, the first electrode fingers having a first average pitch and a first average duty ratio, a largest first average pitch being equal to or greater than two times a thickness of the piezoelectric layer, a first end of each of the one or more parallel resonators being coupled to a path between an input terminal and an output terminal, a second end of each of the one or more parallel resonators being coupled to a ground; and
one or more series resonators connected in series between the input terminal and the output terminal, each of the one or more series resonators including a plurality of second electrode fingers provided on the piezoelectric layer, the second electrode fingers having a second average pitch and a second average duty ratio, the second average duty ratio in at least one series resonator being less than a smallest first average duty ratio,
wherein the one or more series resonators are a plurality of series resonators, the at least one series resonator includes a first series resonator having a largest second average pitch;
wherein a second series resonator among the series resonators has a second average pitch less than the second average pitch of the first series resonator; and
wherein the second series resonator has a second average duty ratio greater than a second average duty ratio in the first series resonator.