US 11,916,542 B2
Acoustic wave filter device and multiplexer using same
Kenichi Uesaka, Nagaokakyo (JP)
Assigned to MURATA MANUFACTURING CO., LTD., Kyoto (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Feb. 18, 2021, as Appl. No. 17/178,301.
Claims priority of application No. 2020-039102 (JP), filed on Mar. 6, 2020.
Prior Publication US 2021/0281244 A1, Sep. 9, 2021
Int. Cl. H03H 9/64 (2006.01); H03H 9/25 (2006.01); H03H 9/72 (2006.01)
CPC H03H 9/6413 (2013.01) [H03H 9/25 (2013.01); H03H 9/6483 (2013.01); H03H 9/72 (2013.01)] 18 Claims
OG exemplary drawing
 
1. An acoustic wave filter device comprising:
a first terminal;
a second terminal;
an inductor connected to the first terminal; and
a longitudinally coupled resonator coupled between the inductor and the second terminal; wherein
the longitudinally coupled resonator includes:
at least one first IDT electrode coupled to the first terminal; and
at least one second IDT electrode connected to the second terminal;
a total capacitance value of the at least one first IDT electrode is greater than a total capacitance value of the at least one second IDT electrode;
each IDT electrode of the at least one first IDT electrode includes a first region in which electrode fingers are provided with a first pitch therebetween and a second region in which electrode fingers are provided with a second pitch therebetween, which is shorter than the first pitch;
each IDT electrode of the at least one second IDT electrode includes a third region in which electrode fingers are provided with a third pitch therebetween and a fourth region in which electrode fingers are provided with a fourth pitch therebetween, which is shorter than the third pitch;
the second region faces the fourth region; and
a number of electrode fingers adjacent to each other with the second pitch therebetween in the second region is greater than a number of electrode fingers adjacent to each other with the fourth pitch therebetween in the fourth region.