I/Q imbalance compensation

1. An apparatus for compensating for in-phase/quadrature (I/Q) phase path imbalance, comprising:

in-phase-path (I-path) circuitry configured to process an I-path signal, the I-path circuitry comprising a first analog filter configured to filter the I-path signal;

quadrature-path (Q-path) circuitry configured to process a Q-path signal, the Q-path circuitry comprising a second analog filter configured to filter the Q-path signal;

an I/Q imbalance compensation circuit configured to process a digital version of the I-path signal and a digital version of the Q-path signal to compensate for mismatch between the I-path circuitry and the Q-path circuitry; and

a first circuit configured to:

determine a compensation parameter for the I/O imbalance compensation circuit to compensate for an initial mismatch between the I-path circuitry and the Q-path circuitry;

determine a coarse adjustment based on the compensation parameter;

apply the coarse adjustment to at least one of the first analog filter or the second analog filter to reduce the initial mismatch between the I-path circuitry and the Q-path circuitry; and

operate the I/Q imbalance compensation circuit to compensate for a residual mismatch between the I-path circuitry and the Q-path circuitry with the coarse adjustment applied to the at least one of the first analog filter or the second analog filter.

2. The apparatus of claim 1 , wherein the first circuit is further configured to:

determine the coarse adjustment based on a correlation between the compensation parameter and mismatch between the first analog filter and the second analog filter.

3. The apparatus of claim 1 , wherein the compensation parameter comprises a value for a frequency dependent coefficient.

4. The apparatus of claim 1 , wherein the compensation parameter comprises a first value for a frequency independent coefficient and a second value for a frequency dependent coefficient.

5. The apparatus of claim 1 , wherein the first circuit is further configured to:

configure the first analog filter and the second analog filter to have a plurality of different mismatches;

determine, for each of the different mismatches, a compensation parameter for the I/Q imbalance compensation circuit; and

determine the coarse adjustment based on the compensation parameters for each of the different mismatches.

6. The apparatus of claim 2 , wherein the first circuit is further configured to:

determine the coarse adjustment based on an estimate that is predicted to minimize the mismatch between the first analog filter and the second analog filter.

7. The apparatus of claim 1 , wherein:

the I-path circuitry further comprises a first frequency mixer configured to up-convert the I-path signal to an I-path radio frequency (RF) signal after the first analog filter filters the I-path signal;

the Q-path circuitry further comprises a second frequency mixer configured to up-convert the Q-path signal to a Q-path RF signal after the second analog filter filters the Q-path signal; and

the apparatus further comprises signal combining circuitry configured to combine the I-path RF signal with the Q-path RF signal to form an RF transmission signal.

8. The apparatus of claim 7 , wherein:

the I-path signal comprises an I-path calibration signal;

the first frequency mixer is configured to up-convert the I-path calibration signal to an I-path RF calibration signal;

the Q-path signal comprises a Q-path calibration signal;

the second frequency mixer is configured to up-convert the Q-path calibration signal to a Q-path RF calibration signal;

the signal combining circuitry is configured to combine the I-path RF calibration signal with the Q-path RF calibration signal to form an RF transmission calibration signal; and

the first circuit is further configured to sample the RF transmission calibration signal to determine the initial mismatch between the I-path circuitry and the Q-path circuitry.

9. The apparatus of claim 7 , wherein the first circuit is further configured to:

sample the I-path signal after it is filtered by the first analog filter but prior to being up-converted by the first frequency mixer;

sample the Q-path signal after it is filtered by the second analog filter but prior to being up-converted by the second frequency mixer; and

determine the initial mismatch between the I-path circuitry and the Q-path circuitry based on the sampled I-path signal and the sampled Q-path signal.

10. The apparatus of claim 1 , wherein:

the I/Q imbalance compensation circuit is configured to process the digital version of the I-path signal and the digital version of the Q-path signal to compensate for the residual mismatch between the I-path circuitry and the Q-path circuitry prior to the I-path signal being filtered by the first analog filter and prior to the Q-path signal being filtered by the second analog filter.

11. The apparatus of claim 1 , wherein:

the I-path circuitry further comprises a third frequency mixer configured to receive and down-convert a radio frequency (RF) signal to generate the I-path signal;

the Q-path circuitry further comprises a fourth frequency mixer configured to receive and down-convert the RF signal to generate the Q-path signal;

the first analog filter is configured to receive the I-path signal from the third frequency mixer; and

the second analog filter is configured to receive the Q-path signal from the fourth frequency mixer.

12. The apparatus of claim 11 , wherein:

the I/Q imbalance compensation circuit is further configured to process the digital version of the I-path signal and the digital version of the Q-path signal to compensate for the residual mismatch between the I-path circuitry and the Q-path circuitry after the I-path signal has been filtered by the first analog filter and after the Q-path signal has been filtered by the second analog filter.

13. The apparatus of claim 1 , wherein:

the I-path circuitry further comprises a fifth frequency mixer; and

the Q-path circuitry further comprises a sixth frequency mixer; and

the apparatus further comprises an oscillator configured to provide an in-phase local oscillator signal to the fifth frequency mixer and a quadrature-phase local oscillator signal to the sixth frequency mixer.

14. A method for compensating for in-phase/quadrature (I/Q) phase path imbalance, the method comprising:

processing an I-path signal with I-path circuitry by filtering the I-path signal with a first analog filter;

processing a Q-path signal with Q-path circuitry by filtering the Q-path signal with a second analog filter;

determining a compensation parameter for an I/Q imbalance compensation circuit to compensate for an initial mismatch between the I-path circuitry and the Q-path circuitry;

determining a coarse adjustment based on the compensation parameter;

applying the coarse adjustment to at least one of the first analog filter or the second analog filter to reduce the initial mismatch between the I-path circuitry and the Q-path circuitry; and

processing a digital version of the I-path signal and a digital version of the Q-path signal to compensate for a residual mismatch between the I-path circuitry and the Q-path circuit with the coarse adjustment applied to the at least one of the first analog filter or the second analog filter.

15. The method of claim 14 , wherein determining the compensation parameter comprises:

determining a first value for a frequency independent coefficient; and

determining a second value for a frequency dependent coefficient.

16. The method of claim 14 , further comprising:

configuring the first analog filter and the second analog filter to have different mismatches;

determining, for each of the different mismatches, a compensation parameter for processing the digital version of the I-path signal and the digital version of the Q-path signal to compensate for the residual mismatch between the I-path circuitry and the Q-path circuitry; and

determining the coarse adjustment based on the compensation parameters for the different mismatches.

17. The method of claim 14 , further comprising:

sampling a first output from the first analog filter and a second output from the second analog filter to determine the initial mismatch between the I-path circuitry and the Q-path circuitry.

18. The method of claim 14 , further comprising:

providing the I-path signal from the first analog filter to a first frequency mixer;

up-converting the I-path signal with the first frequency mixer to form an I-path radio frequency (RF) signal;

providing the Q-path signal from the second analog filter to a second frequency mixer; and

up-converting the Q-path signal with the second frequency mixer to form a Q-path RF signal.

19. The method of claim 14 , further comprising:

processing the digital version of the I-path signal and the digital version of the Q-path signal to compensate for the residual mismatch between the I-path circuitry and the Q-path circuitry prior to filtering the I-path signal with the first analog filter and prior to filtering the Q-path signal with the second analog filter.

20. The method of claim 14 , further comprising:

down-converting a radio frequency (RF) signal with a third frequency mixer to form the I-path signal;

down-converting the RF signal with a fourth frequency mixer to form the Q-path signal;

filtering the I-path signal with the first analog filter after the I-path signal is down-converted by the third frequency mixer; and

filtering the Q-path signal with the second analog filter after the Q-path signal is down-converted by the fourth frequency mixer.

21. The method of claim 20 , further comprising:

processing the digital version of the I-path signal and the digital version of the Q-path signal to compensate for the residual mismatch between the I-path circuitry and the Q-path circuitry after filtering the I-path signal with the first analog filter and after filtering the Q-path signal with the second analog filter.

22. A device for processing radio frequency signals, comprising:

I-path circuitry configured to process an I-path signal, the I-path circuitry comprising a first analog filter configured to filter the I-path signal and a first frequency mixer configured to frequency-convert the I-path signal;

Q-path circuitry configured to process a Q-path signal, the Q-path circuitry comprising a second analog filter configured to filter the Q-path signal and a second frequency mixer configured to frequency-convert the Q-path signal;

an oscillator configured to provide an in-phase local oscillator signal to the first frequency mixer and a quadrature-phase local oscillator signal to the second frequency mixer;

non-transitory memory storage; and

one or more processors in communication with the non-transitory memory storage, wherein the non-transitory memory storage store instructions for execution by the one or more processors to:

determine a compensation parameter to compensate for an initial mismatch between the I-path circuitry and the Q-path circuitry;

determine a coarse adjustment based on the compensation parameter;

apply the coarse adjustment to at least one of the first analog filter or the second analog filter to reduce the initial mismatch between the I-path circuitry and the Q-path circuitry; and

process a digital version of the I-path signal and a digital version of the Q-path signal to compensate for a residual mismatch between the I-path circuitry and the Q-path circuitry with the coarse adjustment applied to the at least one of the first analog filter or the second analog filter.

23. The device of claim 22 , wherein the non-transitory memory storage stores the instructions for execution by the one or more processors to:

determine the coarse adjustment based on a correlation between the compensation parameter and mismatch between the first analog filter and the second analog filter.