# US 11,909,382 B2 · Multiplexer, front-end module, and communication device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,382 B2 - Document ID: US11909382B2 - Status: Granted - Kind: B2 - Application number: 17/390,016 - Filed: 2021-07-30 - Published: 2021-11-18 - Granted: 2024-02-20 - Earliest claimed: 2019-03-27 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Masakazu Tani - Web page: https://patentgrep.com/patent/US11909382B2 ## CPC - 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 7/463: {Duplexers} - H03H 9/0004: {Impedance-matching networks (H03H9/145 takes precedence)} - H03H 9/542: {including passive elements (H03H9/545 takes precedence)} - H03H 9/706: {Duplexers} - H03H 9/725: {Duplexers} - H04B 1/40: Circuits - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H04B: TRANSMISSION ## Abstract A multiplexer includes a common terminal, a first reception output terminal, a second reception output terminal, a first filter that is connected between the common terminal and the first reception output terminal, a second filter that is connected between the common terminal and the second reception output terminal and that has a passband different from that of the first filter, and an impedance matching circuit that is disposed between the common terminal and the second filter. The impedance matching circuit includes a serial arm resonator disposed in series on a path connecting the common terminal to the second filter. ## Claims ### Claim 1 A multiplexer comprising: a first common terminal, a first input/output terminal, and a second input/output terminal; a first filter that is connected between the first common terminal and the first input/output terminal; a second filter that is connected between the first common terminal and the second input/output terminal, the second filter having a passband that is different than a passband of the first filter; and an impedance matching circuit that is between the first common terminal and the second filter, wherein the impedance matching circuit comprises a first acoustic wave resonator that is in series on a path connecting the first common terminal to the second filter, wherein the second filter comprises an acoustic wave resonator, and wherein the impedance matching circuit further comprises a first inductor that is between the first common terminal and the first acoustic wave resonator, and that is connected to the first acoustic wave resonator in series. ### Claim 2 (depends on 1) The multiplexer according to claim 1, wherein the impedance matching circuit further comprises a second inductor that is between the first common terminal and the second filter, and that is connected to the first acoustic wave resonator in parallel. ### Claim 3 (depends on 1) The multiplexer according to claim 1, wherein a frequency band that extends from a resonant frequency to an anti-resonant frequency of the first acoustic wave resonator at least partially overlaps the passband of the first filter. ### Claim 4 (depends on 3) The multiplexer according to claim 3, wherein the anti-resonant frequency of the first acoustic wave resonator is in the passband of the first filter. ### Claim 5 (depends on 3) The multiplexer according to claim 3, wherein the frequency band from the resonant frequency to the anti-resonant frequency of the first acoustic wave resonator completely overlaps the passband of the first filter. ### Claim 6 (depends on 1) The multiplexer according to claim 1, wherein an anti-resonant frequency of the first acoustic wave resonator has a lower frequency than the passband of the first filter. ### Claim 7 (depends on 6) The multiplexer according to claim 6, wherein a frequency difference between the anti-resonant frequency of the first acoustic wave resonator and a low frequency end of the passband of the first filter is equal to or less than 10 MHz. ### Claim 8 (depends on 1) The multiplexer according to claim 1, wherein a resonant frequency of the first acoustic wave resonator has a lower frequency than the passband of the first filter, and an anti-resonant frequency of the first acoustic wave resonator is in the passband of the first filter. ### Claim 9 (depends on 1) A front-end module comprising: a third input/output terminal; a switch that has a second common terminal, a first selection terminal, and a second selection terminal, and that is configured to simultaneous connect the second common terminal to the first selection terminal and to the second selection terminal; the multiplexer according to claim 1, the first common terminal being connected to the first selection terminal; and a third filter that is connected between the second selection terminal and the third input/output terminal, the third filter having a passband that is different than the passbands of the first and second filters. ### Claim 10 (depends on 1) A communication device comprising: a radio-frequency signal processing circuit configured to process a radio frequency signal received or transmitted through an antenna; and the multiplexer according to claim 1, the multiplexer being configured to transmit the radio frequency signal between the antenna and the radio-frequency signal processing circuit. ### Claim 11 (depends on 9) A communication device comprising: a radio-frequency signal processing circuit configured to process a radio frequency signal received or transmitted through an antenna; and the front-end module according to claim 9, the front-end module being configured to transmit the radio frequency signal between the antenna and the radio-frequency signal processing circuit. ### Claim 12 A multiplexer comprising: a first common terminal, a first input/output terminal, and a second input/output terminal; a first filter that is connected between the first common terminal and the first input/output terminal; a second filter that is connected between the first common terminal and the second input/output terminal, the second terminal having a passband that is different than a passband of the first filter; and an impedance matching circuit that is between the first common terminal and the second filter, wherein the impedance matching circuit comprises a first acoustic wave resonator that is in series on a path connecting the first common terminal to the second filter, and wherein the impedance matching circuit further comprises an inductor that is between ground and a node on the path, the node being between the first common terminal and the first acoustic wave resonator.