US 12,278,620 B2
Ladder filter and composite filter device
Sunao Yamazaki, Nagaokakyo (JP)
Assigned to MURATA MANUFACTURING CO., LTD., Kyoto (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Jan. 4, 2022, as Appl. No. 17/567,920.
Application 17/567,920 is a continuation of application No. PCT/JP2020/025300, filed on Jun. 26, 2020.
Claims priority of application No. 2019-125775 (JP), filed on Jul. 5, 2019.
Prior Publication US 2022/0131528 A1, Apr. 28, 2022
Int. Cl. H03H 9/56 (2006.01); H03H 9/13 (2006.01); H03H 9/54 (2006.01)
CPC H03H 9/568 (2013.01) [H03H 9/13 (2013.01); H03H 9/542 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A composite filter device comprising:
a plurality of band-pass filters including first ends connected in common to each other, the plurality of band-pass filters including a first band-pass filter including a ladder filter, the ladder filter including:
series arm resonators in a series arm connecting a first terminal and a second terminal;
a first inductor in a first parallel arm;
a second inductor in a second parallel arm, the first parallel arm and the second parallel arm being included in a plurality of parallel arms connecting the series arm and a ground potential; and
parallel arm resonators in parallel arms, respectively, of the plurality of parallel arms and different from the first and second parallel arms; wherein
second end portions of the first inductor and the second inductor nearer to the ground potential than first end portions of the first inductor and the second inductor are connected in common;
the ladder filter further includes a capacitance connected between the ground potential and a section where the first inductor and the second inductor are connected in common;
at least two of the parallel arm resonators are connected between the first and second inductors; and
the plurality of band-pass filters include second and third band-pass filters with pass bands lower than a pass band of the first band-pass filter.