# US 2019/0356302 A1 · Acoustic wave device, duplexer, and filter device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0356302 A1 - Document ID: US20190356302A1 - Status: Published application - Kind: A1 - Application number: 16/527,082 - Filed: 2019-07-31 - Published: 2019-11-21 - Earliest claimed: 2017-02-06 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Junpei YASUDA - Web page: https://patentgrep.com/patent/US20190356302A1 ## CPC - H03H 9/205: having multiple resonators (crystal tuning forks H03H9/21) - H03H 9/6483: {Ladder SAW filters} - H03H 9/02818: {Means for compensation or elimination of undesirable effects} - H03H 9/13: for networks consisting of piezoelectric or electrostrictive materials (for networks using surface acoustic waves H03H9/145) - H03H 9/605: {consisting of a ladder configuration} - H03H 9/70: Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract An acoustic wave device includes an antenna terminal, a signal terminal, and a plurality of resonators that are provided on a piezoelectric substrate. The plurality of resonators include a plurality of series arm resonators on a series arm, and the duty of an IDT electrode of the series arm resonator closest to the antenna terminal among the plurality of series arm resonators is smaller than the duty of an IDT electrode of at least one series arm resonator among the other series arm resonators. ## Claims ### Claim 1 An acoustic wave device comprising: a piezoelectric substrate; an antenna terminal provided on the piezoelectric substrate and electrically connected to an antenna; a signal terminal provided on the piezoelectric substrate, to which a signal is input, and from which a signal is output; and a plurality of resonators provided on the piezoelectric substrate and including an IDT electrode; wherein the plurality of resonators include a plurality of series arm resonators on a series arm electrically connecting the antenna terminal to the signal terminal; and a duty of the IDT electrode of a series arm resonator closest to the antenna terminal among the plurality of series arm resonators is smaller than a duty of the IDT electrode of at least one other series arm resonator among the plurality of series arm resonators. ### Claim 2 (depends on 1) The acoustic wave device according to claim 1, wherein the duty of the IDT electrode of the series arm resonator closest to the antenna terminal is a smallest duty among the duties of the IDT electrodes of the plurality of series arm resonators. ### Claim 3 (depends on 1) The acoustic wave device according to claim 1, wherein other series arm resonators among the plurality of series arm resonators include a series arm resonator with a lower resonant frequency than the series arm resonator closest to the antenna terminal. ### Claim 4 (depends on 1) The acoustic wave device according to claim 1, wherein, among the plurality of series arm resonators, the duty of the IDT electrode of a series arm resonator whose size along an acoustic-wave propagation direction is relatively large is greater than the duty of the IDT electrode of a series arm resonator whose size along the acoustic-wave propagation direction is relatively small. ### Claim 5 (depends on 1) The acoustic wave device according to claim 1, wherein the IDT electrode of a series arm resonator whose size along an acoustic-wave propagation direction is the largest, from among the plurality of series arm resonators, has a duty that is the largest among the duties of the IDT electrodes of all the resonators. ### Claim 6 (depends on 1) The acoustic wave device according to claim 1, wherein a resonator closest to the antenna terminal among the plurality of resonators is the series arm resonator closest to the antenna terminal. ### Claim 7 (depends on 1) The acoustic wave device according to claim 1, wherein the plurality of resonators include the plurality of series arm resonators and a plurality of parallel arm resonators electrically connected between the series arm and the ground potential, and a ladder filter is provided. ### Claim 8 (depends on 1) The acoustic wave device according to claim 1, wherein the plurality of resonators include the plurality of series arm resonators and a vertically coupled resonator acoustic wave filter provided on the series arm. ### Claim 9 (depends on 1) The acoustic wave device according to claim 1, wherein the signal terminal is a receiving terminal and a receiving filter. ### Claim 10 (depends on 1) A duplexer comprising: a first band-pass filter; and a second band-pass filter, which is electrically connected to the first band-pass filter and an antenna terminal to define a common connection; wherein at least one of the first band-pass filter and the second band-pass filter includes the acoustic wave device according to claim 1. ### Claim 11 (depends on 1) A filter device comprising: a first band-pass filter including the acoustic wave device according to claim 1; and at least one second band-pass filter that is electrically connected to the antenna terminal to define a common connection. ### Claim 12 (depends on 1) The acoustic wave device according to claim 1, wherein the piezoelectric substrate is a piezoelectric ceramic or a piezoelectric single crystalline film stacked on a supporting substrate. ### Claim 13 (depends on 1) The acoustic wave device according to claim 1, wherein the plurality of series arm resonators includes at least three series arm resonators. ### Claim 14 (depends on 11) The filter device according to claim 11, wherein a resonant frequency of at least one of the plurality of series arm resonators is outside of a pass band of the first band-pass filter. ### Claim 15 (depends on 11) The filter device according to claim 11, wherein the first band-pass filter and the at least one second band-pass filter have different pass bands from one another. ### Claim 16 (depends on 11) The filter device according to claim 11, wherein the at least one second band-pass filter includes at least two band-pass filters. ### Claim 17 (depends on 10) The duplexer according to claim 10, wherein the first band-pass filter is a receiving filter and the second band-pass filter is a transmitting filter.