# US 2021/0242853 A1 · Multiplexer, front end circuit, 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 2021/0242853 A1 - Document ID: US20210242853A1 - Status: Published application - Kind: A1 - Application number: 17/163,781 - Filed: 2021-02-01 - Published: 2021-08-05 - Earliest claimed: 2020-02-04 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Hirotsugu MORI - Web page: https://patentgrep.com/patent/US20210242853A1 ## CPC - H03H 7/461: {particularly adapted for use in common antenna systems} - H03F 3/195: in integrated circuits - H03F 3/245: {with semiconductor devices only} - H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal - H03H 7/0115: {comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence)} - H03H 9/54: comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64) - H03H 9/706: {Duplexers} - H03H 9/725: {Duplexers} - H04B 1/0057: {using diplexing or multiplexing filters for selecting the desired band} - H04B 1/40: Circuits - H03F 2200/111: the amplifier being a dual or triple band amplifier, e.g. 900 and 1800 MHz, e.g. switched or not switched, simultaneously or not - H03F 2200/294: the amplifier being a low noise amplifier [LNA] - H03F 2200/451: the amplifier being a radio frequency amplifier - H03F 2203/7209: the gated amplifier being switched from a first band to a second band - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H03F: AMPLIFIERS - H04B: TRANSMISSION ## Abstract A multiplexer includes a first acoustic wave filter, a second acoustic wave filter, and an inductor-capacitor (LC) filter each connected to a common terminal. A passband of the second acoustic wave filter is between a passband of the first acoustic wave filter and a passband of the LC filter, a frequency gap between the passband of the second acoustic wave filter and the passband of the LC filter is greater than a frequency gap between the passband of the first acoustic wave filter and the passband of the second acoustic wave filter, the passband of the first acoustic wave filter includes a transmission band of the first communication band, the passband of the LC filter includes a reception band of the first communication band, and the passband of the second acoustic wave filter includes a reception band of a second communication band. ## Claims ### Claim 1 A multiplexer, comprising: a first acoustic wave filter connected to a common terminal, the first acoustic wave filter including an acoustic wave resonator; a second acoustic wave filter connected to the common terminal, the second acoustic wave filter including an acoustic wave resonator; and an inductor-capacitor (LC) filter connected to the common terminal, the LC filter including one or more inductors and one or more capacitors, wherein a passband of the second acoustic wave filter is between a passband of the first acoustic wave filter and a passband of the LC filter, a frequency gap between the passband of the second acoustic wave filter and the passband of the LC filter is greater than a frequency gap between the passband of the first acoustic wave filter and the passband of the second acoustic wave filter, the passband of the first acoustic wave filter includes one of a transmission band or a reception band of a first communication band, the passband of the LC filter includes a remaining one of the transmission band or the reception band of the first communication band, and the passband of the second acoustic wave filter includes one of a transmission band or a reception band of a second communication band different from the first communication band. ### Claim 2 (depends on 1) The multiplexer according to claim 1, wherein the first communication band is a communication band used in 5th Generation New Radio (5G NR). ### Claim 3 (depends on 1) The multiplexer according to claim 1, wherein the passband of the LC filter is wider than the passband of the first acoustic wave filter, and is wider than the passband of the second acoustic wave filter. ### Claim 4 (depends on 1) The multiplexer according to claim 1, wherein the passband of the LC filter is higher than a frequency at which a higher-order mode spurious emission is caused by the first acoustic wave filter. ### Claim 5 (depends on 1) The multiplexer according to claim 1, wherein the passband of the LC filter is higher than the passband of the first acoustic wave filter. ### Claim 6 (depends on 1) The multiplexer according to claim 1, wherein the passband of the LC filter is lower than the passband of the first acoustic wave filter. ### Claim 7 (depends on 1) The multiplexer according to claim 1, wherein the first communication band is at least one of n91, n92, n93, or n94 of 5th Generation New Radio (5G NR). ### Claim 8 (depends on 1) The multiplexer according to claim 1, wherein the second communication band is Band 8 of 4th Generation Long Term Evolution (4G LTE), and the passband of the first acoustic wave filter includes a remaining one of the transmission band or the reception band of the second communication band. ### Claim 9 (depends on 1) The multiplexer according to claim 1, wherein the passband of the first acoustic wave filter includes one of a transmission band or a reception band of a third communication band different from the first communication band and the second communication band, and the third communication band is Band 20 of 4th Generation Long Term Evolution (4G LTE). ### Claim 10 (depends on 1) The multiplexer according to claim 1, wherein the passband of the LC filter includes a fourth communication band different from the first communication band and the second communication band, and the fourth communication band is at least one of n50 or n51 of 5th Generation New Radio (5G NR). ### Claim 11 (depends on 1) The multiplexer according to claim 1, wherein the LC filter includes: one or more series-arm circuits disposed on a signal path that connects the common terminal and a first input/output terminal; and one or more parallel-arm circuits disposed between the signal path and a ground, a first series-arm circuit disposed closest to the common terminal, out of the one or more series-arm circuits, is one of an inductor or a capacitor, and a first parallel-arm circuit disposed closest to the common terminal, out of the one or more parallel-arm circuits, is a remaining one of the inductor or the capacitor. ### Claim 12 A multiplexer, comprising: a first acoustic wave filter connected to a common terminal, the first acoustic wave filter including an acoustic wave resonator; a second acoustic wave filter connected to the common terminal, the second acoustic wave filter including an acoustic wave resonator; and an inductor-capacitor (LC) filter connected to the common terminal, the LC filter including one or more inductors and one or more capacitors, wherein a passband of the second acoustic wave filter is between a passband of the first acoustic wave filter and a passband of the LC filter, a frequency gap between the passband of the second acoustic wave filter and the passband of the LC filter is greater than a frequency gap between the passband of the first acoustic wave filter and the passband of the second acoustic wave filter, the passband of the first acoustic wave filter includes one of a transmission band and a reception band of a first communication band, the passband of the LC filter includes a transmission band of an unlicensed band when the passband of the first acoustic wave filter includes the reception band of the first communication band, and includes a reception band of the unlicensed band when the passband of the first acoustic wave filter includes the transmission band of the first communication band, the unlicensed band being a band for assisting transfer of a signal in the first communication band, and the passband of the second acoustic wave filter includes one of a transmission band or a reception band of a second communication band different from the first communication band. ### Claim 13 (depends on 10) A front end circuit, comprising: the multiplexer according to claim 10; a low noise amplifier configured to amplify a reception signal in the fourth communication band, and a reception signal in the remaining one of the transmission band or the reception band of the first communication band; a power amplifier configured to amplify a transmission signal in the fourth communication band; and a first switch configured to switch a connection of the LC filter between the low noise amplifier and the power amplifier. ### Claim 14 (depends on 1) A communication device, comprising: an antenna; a radio frequency (RF) signal processing circuit configured to process radio frequency signals transmitted and received by the antenna; and the multiplexer according to claim 1 configured to transfer the radio frequency signals between the antenna and the RF signal processing circuit.