# US 12,003,270 B2 · Passive intermodulation distortion filtering > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,003,270 B2 - Document ID: US12003270B2 - Status: Granted - Kind: B2 - Application number: 17/469,755 - Filed: 2021-09-08 - Published: 2023-03-09 - Granted: 2024-06-04 - Earliest claimed: 2021-09-08 - Assignees: QUALCOMM Incorporated - Applicants: Qualcomm Incorporated - Inventors: Rimon Mansour; Samel Celebi - Web page: https://patentgrep.com/patent/US12003270B2 ## CPC - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H04B 1/50: using different frequencies for the two directions of communication - H04B 1/525: with means for reducing leakage of transmitter signal into the receiver - H04L 25/03891: {Spatial equalizers (MIMO diversity systems H04B7/0413)} - H04B 2001/045: {with means for improving efficiency} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract An apparatus is disclosed for passive intermodulation distortion filtering. The apparatus includes a radio-frequency front-end circuit. The radio-frequency front-end circuit includes a transmit filter circuit and a receive filter circuit. The transmit filter circuit includes a passive circuit configured to combine at least two radio-frequency transmit signals associated with different transmit frequency bands. The transmit filter circuit also includes a filter coupled between the passive circuit and a first feed of an antenna. The filter is configured to attenuate frequencies associated with a receive frequency band. The receive filter circuit is coupled to a second feed of the antenna and is configured to pass the frequencies associated with the receive frequency band. ## Claims ### Claim 1 An apparatus comprising: a radio-frequency front-end circuit comprising: a transmit filter circuit comprising: a passive circuit configured to combine at least two radio-frequency transmit signals associated with different transmit frequency bands; and a filter coupled between the passive circuit and a first feed of an antenna, the filter configured to attenuate frequencies associated with a receive frequency band; and a receive filter circuit coupled to a second feed of the antenna and configured to pass the frequencies associated with the receive frequency band. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the passive circuit comprises multiple band-pass filters having different passbands respectively associated with the different transmit frequency bands. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the multiple band-pass filters form one of the following: a diplexer; a triplexer; or a quadplexer. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein: the multiple band-pass filters comprise the diplexer; the diplexer is associated with two transmit frequency bands of the different transmit frequency bands; and the receive filter circuit comprises another diplexer associated with the receive frequency band and another receive frequency band. ### Claim 5 (depends on 2) The apparatus of claim 2, wherein the multiple band-pass filters comprise multiple cavity filters. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein a transmit frequency band of the different transmit frequency bands and the receive frequency band represent frequencies associated with a same communication band, the communication band associated with frequency-division-duplexing. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein: the radio-frequency front-end circuit comprises: a first transmit path associated with a first transmit frequency band of the different transmit frequency bands and coupled to a first input of the passive circuit; a second transmit path associated with a second transmit frequency band of the different transmit frequency bands and coupled to a second input of the passive circuit; and at least one receive path associated with the receive frequency band, the at least one receive path coupled to an output of the receive filter circuit; and the filter is configured to have a passband that passes signals associated with the first transmit frequency band and the second transmit frequency band and that attenuates other signals associated with the receive frequency band. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein an intermodulation product of the first transmit frequency band and the second transmit frequency band is within the receive frequency band. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein: the first transmit frequency band comprises downlink frequencies associated with communication band 2; the second transmit frequency band comprises downlink frequencies associated with communication band 4; and the receive frequency band comprises uplink frequencies associated with the communication band 4. ### Claim 10 (depends on 7) The apparatus of claim 7, wherein a harmonic of at least one of the first transmit frequency band or the second transmit frequency band is within the receive frequency band. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein: the first transmit path comprises a first amplifier coupled to the first input of the passive circuit; the second transmit path comprises a second amplifier coupled to the second input of the passive circuit; and the at least one receive path comprises a third amplifier coupled to the output of the receive filter circuit. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein the filter comprises at least one of the following: a low-pass filter; a high-pass filter; a band-pass filter; or a band-stop filter. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the filter comprises at least one cavity filter. ### Claim 14 (depends on 1) The apparatus of claim 1, wherein the receive filter circuit comprises a multiplexer. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the multiplexer comprises multiple cavity filters or multiple acoustic filters. ### Claim 16 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises a base station. ### Claim 17 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises a computing device. ### Claim 18 An apparatus for filtering, the apparatus comprising: passive means for generating a composite transmit signal by combining multiple radio-frequency transmit signals associated with different transmit frequency bands; means for attenuating one or more frequencies within the composite transmit signal that are associated with a receive frequency band to generate a filtered composite transmit signal; and means for transmitting the filtered composite transmit signal using a feed that is separate from another feed used to receive a radio-frequency receive signal associated with the receive frequency band. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein: the composite transmit signal includes passive intermodulation distortion associated with an intermodulation product of the different transmit frequency bands; and the means for attenuating the one or more frequencies within the composite transmit signal is configured to attenuate the passive intermodulation distortion within the receive frequency band. ### Claim 20 (depends on 18) The apparatus of claim 18, wherein the passive means comprises: means for passing frequencies associated with a first transmit frequency band of the different transmit frequency bands; means for passing frequencies associated with a second transmit frequency band of the different transmit frequency bands; and means for combining the frequencies associated with the first transmit frequency band and the frequencies associated with the second transmit frequency band. ### Claim 21 A method for filtering, the method comprising: accepting multiple radio-frequency transmit signals associated with different transmit frequency bands; passively combining the multiple radio-frequency transmit signals together to generate a composite transmit signal; attenuating one or more frequencies within the composite transmit signal that are associated with a receive frequency band to generate a filtered composite transmit signal; and passing the filtered composite transmit signal to a feed of an antenna that is separate from another feed of the antenna associated with receiving a radio-frequency receive signal, the radio-frequency receive signal associated with the receive frequency band. ### Claim 22 (depends on 21) The method of claim 21, wherein the attenuating the frequencies comprises attenuating an intermodulation product associated with a combination of the different transmit frequency bands. ### Claim 23 (depends on 21) The method of claim 21, wherein the attenuating the frequencies comprises at least one of the following: attenuating frequencies that are higher than frequencies associated with the different transmit frequency bands; attenuating frequencies that are lower than the frequencies associated with the different transmit frequency bands; attenuating frequencies that are lower than and higher than the frequencies associated with the different transmit frequency bands; or attenuating frequencies that are between the frequencies associated with the different transmit frequency bands. ### Claim 24 A radio-frequency front-end circuit comprising: a multiplexer comprising multiple band-pass filters configured to have different frequency responses associated with different transmit frequency bands; and a filter coupled to an output of the multiplexer, the filter configured to: be coupled to a feed of an antenna that is separate from another feed that is to be used to receive a radio-frequency receive signal; and have a frequency response that represents a combination of the different frequency responses of the multiple band-pass filters. ### Claim 25 (depends on 24) The radio-frequency front-end circuit of claim 24, wherein the frequency response of the filter attenuates frequencies associated with a receive frequency band of the radio-frequency receive signal. ### Claim 26 (depends on 24) The radio-frequency front-end circuit of claim 24, wherein the frequency response of the filter passes frequencies associated with the different transmit frequency bands. ### Claim 27 (depends on 24) The radio-frequency front-end circuit of claim 24, wherein: the multiplexer is configured to generate a composite transmit signal by combining multiple radio-frequency transmit signals associated with the different transmit frequency bands; and the filter is configured to attenuate an intermodulation product within the composite transmit signal, the intermodulation product associated with a combination of the different transmit frequency bands and having a frequency within a receive frequency band of the radio-frequency receive signal. ### Claim 28 (depends on 24) The radio-frequency front-end circuit of claim 24, further comprising: multiple power amplifiers respectively coupled to the multiple band-pass filters. ### Claim 29 (depends on 24) The radio-frequency front-end circuit of claim 24, further comprising: a receive filter circuit configured to: accept the radio-frequency receive signal from the other feed of the antenna; and pass frequencies associated with a receive frequency band. ### Claim 30 (depends on 29) The radio-frequency front-end circuit of claim 29, wherein the receive filter circuit comprises a diplexer.