# US 11,909,428 B2 · Tunable filter with harmonic rejection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,428 B2 - Document ID: US11909428B2 - Status: Granted - Kind: B2 - Application number: 17/351,984 - Filed: 2021-06-18 - Published: 2021-12-30 - Granted: 2024-02-20 - Earliest claimed: 2020-06-30 - Assignees: Skyworks Solutions, Inc. - Applicants: Skyworks Solutions, Inc. - Inventors: Kun Chen; Joshua Kawika Ellis; Shayan Farahvash; Haibo Cao - Web page: https://patentgrep.com/patent/US11909428B2 ## CPC - H04B 1/10: Means associated with receiver for limiting or suppressing noise or interference - H03H 7/0115: {comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence)} - H03H 7/0153: {Electrical filters; Controlling thereof} - H03H 7/075: Ladder networks, e.g. electric wave filters - H03H 7/09: Filters comprising mutual inductance - H03H 7/1758: {Series LC in shunt or branch path (H03H7/1791 takes precedence)} - H03H 7/1766: {Parallel LC in series path (H03H7/1783 takes precedence)} - H04B 1/1027: {assessing signal quality or detecting noise/interference for the received signal} - H04B: TRANSMISSION - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract Aspects of this disclosure relate to a tunable filter with harmonic rejection. The tunable filter includes mutually coupled inductors and a tunable capacitance circuit electrically connected to at least one of the mutually coupled inductors. The tunable capacitance circuit includes N switches configured to adjust effective capacitance of the tunable capacitance circuit to tune harmonic rejection of the tunable filter for at least 2×2N harmonics. The tunable filter can filter a radio frequency signal. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed. ## Claims ### Claim 1 A tunable filter with harmonic rejection, the tunable filter comprising: a first inductor; a second inductor mutually coupled with the first inductor; and a tunable capacitance circuit electrically connected to the first inductor, the tunable capacitance circuit including N switches configured to adjust effective capacitance of the tunable capacitance circuit to tune harmonic rejection of the tunable filter for at least 2×2N harmonics, N being a positive integer greater than 1, and the tunable filter being arranged to filter a radio frequency signal. ### Claim 2 (depends on 1) The tunable filter of claim 1 wherein the N switches are configured to tune harmonic rejection of the tunable filter for at least 3×2N harmonics. ### Claim 3 (depends on 1) The tunable filter of claim 1 wherein the tunable capacitance circuit is in parallel with the first inductor. ### Claim 4 (depends on 3) The tunable filter of claim 3 further comprising a capacitance in parallel with the second inductor and a shunt capacitance between the first and second inductors, the first inductor being in series with the second inductor. ### Claim 5 (depends on 1) The tunable filter of claim 1 wherein changing a state of a first switch of the N switches changes location of at least two notches in a frequency response of the tunable filter. ### Claim 6 (depends on 1) The tunable filter of claim 1 wherein changing a state of a first switch of the N switches changes location of at least three notches in a frequency response of the tunable filter. ### Claim 7 (depends on 1) The tunable filter of claim 1 wherein the second inductor is a shunt inductor. ### Claim 8 (depends on 7) The tunable filter of claim 7 wherein the tunable capacitance circuit is in parallel with the first inductor. ### Claim 9 (depends on 8) The tunable filter of claim 8 further comprising a shunt capacitor in series with the second inductor, the shunt capacitor electrically connected to the first inductor by way of the second inductor. ### Claim 10 (depends on 1) The tunable filter of claim 1 wherein the 2×2N harmonics include at least one second harmonic and at least one third harmonic. ### Claim 11 (depends on 1) The tunable filter of claim 1 wherein the 2×2N harmonics include at least one harmonic associated with a fifth generation New Radio operating band. ### Claim 12 (depends on 1) The tunable filter of claim 1 wherein the 2×2N harmonics include at least one harmonic associated with a fifth generation New Radio operating band and at least one harmonic associated with a fourth generation Long Term Evolution operating band. ### Claim 13 A wireless communication device comprising: a radio frequency front end including a tunable filter, the tunable filter including a first inductor, a second inductor mutually coupled with the first inductor, and a tunable capacitance circuit electrically connected to the first inductor, the tunable capacitance circuit including N switches configured to adjust effective capacitance of the tunable capacitance circuit to tune harmonic rejection of the tunable filter for at least 2×2N harmonics, N being a positive integer greater than 1, and the tunable filter being arranged to filter a radio frequency signal; and an antenna in communication with the radio frequency front end. ### Claim 14 (depends on 13) The wireless communication device of claim 13 wherein the antenna is arranged to transmit a radio frequency signal filtered by the tunable filter. ### Claim 15 (depends on 13) The wireless communication device of claim 13 wherein the radio frequency front end includes an antenna switch, the tunable filter coupled between the antenna switch and the antenna. ### Claim 16 (depends on 13) The wireless communication device of claim 13 wherein the radio frequency front end includes a power amplifier and a band select switch, the tunable filter coupled between the power amplifier and the band select switch. ### Claim 17 (depends on 13) The wireless communication device of claim 13 wherein the wireless communication device is configured to implement dual connectivity, the tunable filter is configured to provide rejection for the dual connectivity. ### Claim 18 (depends on 13) The wireless communication device of claim 13 wherein the wireless communication device is configured to implement carrier aggregations, the tunable filter is configured to provide rejection for the carrier aggregations. ### Claim 19 (depends on 13) The wireless communication device of claim 13 wherein N is at least 4. ### Claim 20 A radio frequency system comprising: an antenna switch; a tunable filter including a first inductor, a second inductor mutually coupled with the first inductor, and a tunable capacitance circuit electrically connected to the first inductor, the tunable capacitance circuit including N switches configured to adjust effective capacitance of the tunable capacitance circuit to tune harmonic rejection of the tunable filter for at least 2×2N harmonics, N being a positive integer greater than 1, and the tunable filter being arranged to filter a radio frequency signal; and an antenna port, the tunable filter being coupled in a signal path between the antenna switch and the antenna port.