Circuit, controller and methods for dynamic estimation and cancellation of phase and gain imbalances in quadrature signal paths of a receiver
View Patent ↗A controller and a circuit work together to enable a selective and dynamic adjustment to correct phase and gain imbalances in quadrature signal paths of a receiver. Under select conditions, it has been determined that statistical estimates of gain and phase imbalance can be applied to adjust signals in the quadrature signal paths of a receiver. The controller validates the select conditions before updating the estimate of the gain imbalance and the estimate of the phase imbalance. The controller directs a compensator under select operating conditions such that validated dynamic estimates of the gain and phase imbalance or calibration data is applied to the quadrature signal paths. The controller disables the compensator and enables an estimator and a calculator when estimates are unavailable for the present operating conditions.
1. A method for dynamic estimation and cancellation of phase and gain imbalance in quadrature signal paths of a receiver, comprising:
removing any DC offset present in the quadrature signal paths;
applying an initial gain compensation value and an initial phase compensation value;
generating an estimate of gain imbalance and an estimate of phase imbalance present between the quadrature signal paths
comprises:
determining when a data length reaches a first threshold value;
determining when the auto correlation of the second signal exceeds a second threshold value;
determining a present frequency band of operation;
determining a present range of mixer gain; and
saving the estimate of the gain imbalance and the estimate of the phase imbalance such that the presence of the estimate of the gain imbalance and the estimate of the phase imbalance can be confirmed and the estimate of the phase imbalance and the estimate of the gain imbalance retrieved responsive to the frequency band and the range of mixer gain;
generating a modified gain compensation value as a function of the estimate of the gain imbalance and the initial gain compensation value;
generating a modified phase compensation value as a function of the estimate of the phase imbalance and the initial phase compensation value; and
making a determination whether to apply the modified gain compensation and the modified phase compensation values in the quadrature signal paths of the receiver.
2. The method of claim 1 , wherein generating an estimate of the gain imbalance comprises computing an auto correlation of a first signal in the I signal path, an auto correlation of a second signal in the Q signal path and a cross correlation of the first and second signals in the quadrature signal paths.
3. The method of claim 2 , wherein generating an estimate of the phase imbalance further comprises computing a ratio of the cross correlation of the first and second signals in the quadrature signal paths to the auto correlation of the second signal in the Q signal path.
4. The method of claim 2 , wherein generating an estimate of the gain imbalance further comprises computing a ratio of the auto correlation of the first signal in the I signal path to the auto correlation of the second signal in the Q signal path.
5. The method of claim 1 , further comprising:
repeating the generating of an estimate of gain imbalance and an estimate of phase imbalance, the generating of a modified gain compensation value, the generating of a modified phase compensation value and making a determination whether to apply the modified gain compensation value and the modified phase compensation value for a predetermined time.
6. The method of claim 1 , further comprising:
applying the modified gain compensation value and the modified phase compensation value prior to a reception of a subsequent data burst.
7. The method of claim 1 , wherein when a determination has been made to apply the gain compensation value and the phase compensation value, further comprising:
determining which of the I signal path and the Q signal path should be gain adjusted.
8. The method of claim 1 , wherein making a determination whether to apply the modified gain compensation and the modified phase compensation values in the quadrature signal paths of the receiver comprises:
determining when the estimate of the gain imbalance and the estimate of the phase imbalance exist for the frequency band and the range of mixer gain and applying the same; and
otherwise, determining when calibration data exists for the frequency band and the range of mixer gain and applying the same.