Compensating for frequency-dependent i-q phase imbalance

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.

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.

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.