System and method for IQ mismatch calibration and compensation
A method for providing IQ mismatch (IQMM) compensation includes: sending a single tone signal at an original frequency; determining a first response of an impaired signal at the original frequency and a second response of the impaired signal at a corresponding image frequency; determining an estimate of a frequency response of the compensation filter at the original frequency based on the first response and the second response; repeating the steps of sending the single tone signal, determining the first response and the second response, and determining the estimate of the frequency response of the compensation filter by sweeping the single tone signal at a plurality of steps to determine a snapshot of the frequency response of the compensation filter; converting the frequency response of the compensation filter to a plurality of time-domain filter taps of the compensation filter by performing a pseudo-inverse of a time-to-frequency conversion matrix; and determining a time delay that provides a minimal LSE for the corresponding time domain filter taps.
1. A method for providing IQ mismatch (IQMM) compensation, the method comprising:
estimating filter coefficients corresponding to a plurality of time-domain filter taps of a compensation filter except a time delay tap during initial calibration based on a static calibration scheme according to a frequency-dependent IQMM (FD-IQMM) calibration;
setting each of the plurality of time-domain filter taps with a corresponding estimated filter coefficient;
setting an initial value for the time delay tap to zero or based an estimated value obtained using the static calibration scheme; and
adaptively estimating a filter coefficient for the time delay tap during signal reception operation after the initial calibration based on an iterative calibration scheme using the compensation filter according to a frequency-independent IQMM (FI-IQMM) calibration.
2. The method of claim 1 , wherein the FD-IQMM calibration is bandwidth dependent, and the FI-IQMM calibration is channel or band dependent, and
wherein the FD-IQMM calibration and the FI-IQMM calibration are separately performed.
3. The method of claim 1 , wherein the compensation filter is a complex-valued filter.
4. The method of claim 1 , wherein the compensation filter is a real-valued filter including a real-valued scaling factor that feeds a delayed version of an in-phase (I) path into an output of a real-valued filter of a quadrature (Q) path.
5. The method of claim 1 , wherein the compensation filter is implemented in a receiver of a wireless communication system.
6. The method of claim 1 , wherein the compensation filter includes a baseband digital filter.
7. The method of claim 1 , further comprising selecting a finite number of time-domain filter taps among the plurality of time-domain filter taps.
8. The method of claim 7 , wherein the finite number of time-domain filter taps includes one or more positive filter taps.
9. The method of claim 8 , further comprising adding an extra time delay in a feedforward path of the compensation filter to include a negative filter tap.
10. The method of claim 1 , wherein the time delay tap is estimated based on a plurality of minimal least square errors (LSEs) for the corresponding time-domain filter taps.
11. An apparatus comprising:
a signal generator for generating and sending a single tone signal at an original frequency;
a compensator including a time delay and a plurality of time-domain filter taps; and
a compensation logic for performing a static calibration of the compensator,
wherein the compensation logic is configured to:
estimate filter coefficients corresponding to the plurality of time-domain filter taps of a compensation filter except a time delay tap during initial calibration based on a static calibration scheme according to a frequency-dependent IQMM (FD-IQMM) calibration;
set each of the plurality of time-domain filter taps with a corresponding estimated filter coefficient;
set an initial value for the time delay tap to zero or based an estimated value obtained using the static calibration scheme; and
adaptively estimate a filter coefficient for the time delay tap during signal reception operation after the initial calibration based on an iterative calibration scheme using the compensation filter according to a frequency-independent IQMM (FI-IQMM) calibration.
12. The apparatus of claim 11 , wherein the FD-IQMM calibration is bandwidth dependent, and the FI-IQMM calibration is channel or band dependent, and
wherein the FD-IQMM calibration and the FI-IQMM calibration are separately performed.
13. The apparatus of claim 11 , wherein the compensation filter is a complex-valued filter.
14. The apparatus of claim 11 , wherein the compensation filter is a real-valued filter including a real-valued scaling factor that feeds a delayed version of an in-phase (I) path into an output of a real-valued filter of a quadrature (Q) path.
15. The apparatus of claim 11 , wherein the compensation filter is implemented in a receiver of a wireless communication system.
16. The apparatus of claim 11 , wherein the compensation filter includes a baseband digital filter.
17. The apparatus of claim 11 , wherein the compensation logic is further configured to select a finite number of time-domain filter taps among the plurality of time-domain filter taps.
18. The apparatus of claim 17 , wherein the finite number of time-domain filter taps includes one or more positive filter taps.
19. The apparatus of claim 18 , wherein the compensation logic is further configured to add an extra time delay in a feedforward path of the compensation filter to include a negative filter tap.
20. The apparatus of claim 11 , wherein the time delay tap is estimated based on a plurality of minimal least square errors (LSEs) for the corresponding time-domain filter taps.