Patent ID: 11929737
Assignee: MURATA MANUFACTURING CO., LTD.
Field: Basic communication processes (Electrical engineering)
Classification: CPC H | IPC H

Claim 8:
9. The band pass acoustic wave filter according to claim 8, wherein
the acoustic wave resonator of the third serial arm resonance circuit includes an IDT electrode provided on a substrate having piezoelectricity;
the IDT electrode includes a pair of comb-shaped electrodes each including a plurality of electrode fingers extending in a direction intersecting with an acoustic wave propagation direction and in parallel or substantially in parallel to one another, and busbar electrodes connecting ends of electrode fingers of the plurality of electrode fingers to each other;
where, among the plurality of electrode fingers:
a first electrode finger which is not connected to the busbar electrodes is defined as a first withdrawal electrode,
a second electrode finger having a maximum electrode finger width, and having an electrode finger width two or more times an average electrode finger width of the plurality of electrode fingers excluding the second electrode finger is defined as a second withdrawal electrode, and
a third electrode finger connected to a same one of the busbar electrodes as adjacent electrode fingers on both adjacent sides in the acoustic wave propagation direction is defined as a third withdrawal electrode;

the third serial arm resonance circuit includes any of the first withdrawal electrode, the second withdrawal electrode, and the third withdrawal electrode;
a resonant frequency of the third serial arm resonance circuit is on the lower-frequency side than the pass band; and
an anti-resonant frequency of the third serial arm resonance circuit is on the higher-frequency side than the pass band.