# US 11,310,086 B2 · Compensating for frequency-dependent I-Q phase imbalance > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,310,086 B2 - Document ID: US11310086B2 - Status: Granted - Kind: B2 - Application number: 17/222,016 - Filed: 2021-04-05 - Published: 2021-08-05 - Granted: 2022-04-19 - Earliest claimed: 2019-12-31 - Assignees: Hughes Network Systems, LLC - Applicants: Hughes Network Systems, LLC - Inventors: Neal D. Becker - Web page: https://patentgrep.com/patent/US11310086B2 ## CPC - H04L 27/227: using coherent demodulation - H04L 27/364: {Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels} - H04B 1/16: Circuits - H04L 2027/0024: {at the receiver end} - H04L 2027/0044: {Control loops for carrier regulation} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for compensating for frequency-dependent I-Q imbalance. In some implementations, a radio receiver includes an in-phase mixer configured to generate an in-phase (I) signal and a quadrature mixer configured to generate a quadrature (Q) signal. A first analog-to-digital (A/D) converter is configured to generate first digital samples from one of the I signal and the Q signal. A second analog-to-digital (A/D) converter is configured to generate second digital samples from the other of the I signal and the Q signal. A compensation system includes a feedback loop configured to compensate for frequency-dependent I-Q imbalance based on results, for each of multiple of the first digital samples, of cross-correlation of the first digital sample with each of multiple of the second digital samples. ## Claims ### Claim 1 A radio receiver, comprising: an in-phase mixer configured to generate an in-phase (I) signal; a quadrature mixer configured to generate a quadrature (Q) signal; a first analog-to-digital (A/D) converter configured to generate first digital samples from one of the I signal and the Q signal; a second analog-to-digital (A/D) converter configured to generate second digital samples from the other of the I signal and the Q signal; and a compensation system comprising a control loop configured to compensate for frequency-dependent I-Q imbalance based on results, for each of multiple of the first digital samples, of cross-correlation of the first digital sample with each of multiple of the second digital samples that are offset in time from the first digital sample. ### Claim 2 (depends on 1) The radio receiver of claim 1, wherein the control loop comprises one of a feedback control loop or a feedforward control loop. ### Claim 3 (depends on 1) The radio receiver of claim 1, wherein the control loop is configured to compensate for the frequency-dependent I-Q imbalance based on additional results of cross-correlation of each first digital sample with a corresponding second digital sample that is not offset in time from the first digital sample. ### Claim 4 (depends on 1) The radio receiver of claim 1, wherein each of the multiple of the second digital samples for each first digital sample has a time index that is different from a time index of the first digital sample. ### Claim 5 (depends on 1) The radio receiver of claim 1, wherein: the control loop comprises a plurality of correlator stages; and each correlator stage generates, for each of the multiple first digital samples, a cross-correlation result by cross-correlating the first digital sample with a respective second digital sample of the multiple second digital samples. ### Claim 6 (depends on 5) The radio receiver of claim 5, wherein each correlator stage comprises: a first mixer configured to generate a product of one of the first digital samples and the respective second digital sample; a control element configured to generate the cross-correlation result, including integrating a plurality of products generated by the first mixer over time; and a second mixer configured to generate an adjusted second digital sample by multiplying the cross-correlation result by the second digital sample. ### Claim 7 (depends on 1) The radio receiver of claim 1, wherein the multiple second digital samples for each first digital sample comprises a predetermined quantity of second digital samples within a limited window corresponding to the first digital sample, the limited window having a position based on a time index of the first digital sample and including the multiple second digital samples. ### Claim 8 A method comprising: obtaining an in-phase (I) signal and a quadrature (Q) signal generated from an input signal; obtaining first digital samples from one of the I signal and the Q signal; obtaining second digital samples from the other of the I signal and the Q signal; and compensating for frequency-dependent I-Q imbalance by: determining, for each of multiple of the first digital samples, cross-correlations of the first digital sample with respect to each of multiple of the second digital samples that are offset in time from the first digital sample; operating a control loop based on the cross-correlations; and adjusting the I signal or the Q signal based on the control loop. ### Claim 9 (depends on 8) The method of claim 8, wherein the control loop comprises one of a feedback control loop or a feedforward control loop. ### Claim 10 (depends on 8) The method of claim 8, wherein the control loop compensates for the frequency-dependent I-Q imbalance based on additional results of cross-correlation of each first digital sample with a corresponding second digital sample that is not offset in time from the first digital sample. ### Claim 11 (depends on 8) The method of claim 8, wherein each of the multiple of the second digital samples for each first digital sample has a time index that is different from a time index of the first digital sample. ### Claim 12 (depends on 8) The method of claim 8, wherein: the control loop comprises a plurality of correlator stages; and each correlator stage generates, for each of the multiple first digital samples, a cross-correlation result by cross-correlating the first digital sample with a respective second digital sample of the multiple second digital samples. ### Claim 13 (depends on 12) The method of claim 12, wherein each correlator stage comprises: a first mixer configured to generate a product of one of the first digital sample and the respective second digital sample; a control element configured to generate the cross-correlation result, including integrating a plurality of products generated by the first mixer over time; and a second mixer configured to generate an adjusted second digital sample by multiplying the cross-correlation result by the second digital sample. ### Claim 14 (depends on 8) The method of claim 8, wherein the multiple second digital samples for each first digital sample comprises a predetermined quantity of second digital samples within a limited window corresponding to the first digital sample, the limited window having a position based on a time index of the first digital sample and including the multiple second digital samples. ### Claim 15 A non-transitory computer readable medium comprising instructions that, when executed by a data processing apparatus, cause the data processing apparatus to perform operations comprising: obtaining an in-phase (I) signal and a quadrature (Q) signal generated from an input signal; obtaining first digital samples from one of the I signal and the Q signal; obtaining second digital samples from the other of the I signal and the Q signal; and compensating for frequency-dependent I-Q imbalance by: determining, for each of multiple of the first digital samples, cross-correlations of the first digital sample with respect to each of multiple of the second digital samples that are offset in time from the first digital sample; operating a control loop based on the cross-correlations; and adjusting the I signal or the Q signal based on the control loop. ### Claim 16 (depends on 15) The non-transitory computer readable medium of claim 15, wherein the control loop comprises one of a feedback control loop or a feedforward control loop. ### Claim 17 (depends on 15) The non-transitory computer readable medium of claim 15, wherein the control loop compensates for the frequency-dependent I-Q imbalance based on additional results of cross-correlation of each first digital sample with a corresponding second digital sample that is not offset in time from the first digital sample. ### Claim 18 (depends on 15) The non-transitory computer readable medium of claim 15, wherein each of the multiple of the second digital samples for each first digital sample has a time index that is different from a time index of the first digital sample. ### Claim 19 (depends on 15) The non-transitory computer readable medium of claim 15, wherein: the control loop comprises a plurality of correlator stages; and each correlator stage generates, for each of the multiple first digital samples, a cross-correlation result by cross-correlating the first digital sample with a respective second digital sample of the multiple second digital samples. ### Claim 20 (depends on 19) The non-transitory computer readable medium of claim 19, wherein each correlator stage comprises: a first mixer configured to generate a product of one of the first digital sample and the respective second digital sample; a control element configured to generate the cross-correlation result, including integrating a plurality of products generated by the first mixer over time; and a second mixer configured to generate an adjusted second digital sample by multiplying the cross-correlation result by the second digital sample.