Systems and methods to provide wideband magnitude and phase imbalance calibration and compensation in quadrature receivers

• US 20030206603A1
• Filed: 05/03/2002
• Published: 11/06/2003
• Est. Priority Date: 05/03/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Atheros Communications Incorporated (Qualcomm, Inc.)
• Inventors: Husted, Paul J.
• Granted Patent: US 7,158,586 B2
• Time in Patent Office: Days
• US Class Current: 375/324
• CPC Class Codes: H04L 2027/0016 Stabilisation of local oscillators
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal
• CPC Class Codes: H04L 27/3872 Compensation for phase rotation in the demodulated signal

Abstract

Systems and methods for passively calibrating and correcting for I/Q mismatch in a quadrature receiver without the necessity of modifying the analog portion of the receiver by adding calibration signals or correction circuitry are presented. The passive I/Q mismatch calibration system proceeds using normally received incoming transmitted data signals to obtain statistical information on which to base I/Q mismatch compensation factors. The I/Q mismatch compensation factors can be used to adjust the magnitude and phase response in the time domain or the frequency domain, the analog or the digital portion of the receiver. Depending on the embodiment, the passive I/Q mismatch calibration system can calibrate frequency dependent gain or magnitude imbalance, frequency independent magnitude imbalance, frequency dependent phase imbalance, and frequency independent phase imbalance or combinations or these.

Claims

1. A method of calibrating and compensating for magnitude and phase imbalances in a quadrature receiver, comprising the steps of:

generating first correction factors from in-phase and quadrature digital signals, the signals being derived from a received signal, the received signal being other than a signal received solely for the purposes of calibration; and

compensating for one or more of frequency independent magnitude imbalance and frequency independent phase imbalance using at least some of the first correction factors.

2. The method according to claim 1, wherein the received signal comprises a received modulated signal.

3. The method according to claim 1, wherein the calibrating and compensating for magnitude and phase imbalances is performed without the use of a specifically configured I/Q calibration signal but rather by examining regularly received signals that carry data.

4. The method according to claim 1, further comprising, prior to the step of generating:

performing analog to digital conversion on respective in-phase and quadrature analog signals along respective in-phase and quadrature signal paths to form the in-phase and quadrature digital signals, the in-phase and quadrature analog signals being derived from the received signal.

5. The method according to claim 4, wherein the received signal comprises an analog signal received at an antenna of the quadrature receiver in a wireless communications system.

6. The method according to claim 4, wherein the received signal comprises an analog signal received at the quadrature receiver in a wireline communications system.

7. The method according to claim 4, further comprising, prior to the step of generating:

simultaneously configuring an analog in-phase test signal along the in-phase signal path and an analog quadrature test signal along the quadrature signal path, the respective in-phase and quadrature test signals configured to be approximately in phase with one another.

8. The method according to claim 7, wherein the step of simultaneously configuring comprises:

switching local oscillator signals from a local oscillator at in-phase and quadrature mixers so that the local oscillator signals have approximately the same phase when presented to respective in-phase and quadrature mixers to simultaneously configure the analog in-phase and quadrature test signals respectively.

9. The method according to claim 7, further comprising, prior to the step of performing:

converting the respective analog in-phase and quadrature test signals to respective digital in-phase and quadrature test signals.

10. The method according to claim 9, further comprising, prior to the step of generating:

for each of the digital in-phase and quadrature test signals,

decomposing the digital test signals into one or more respective component digital test signals corresponding to one or more respective frequencies at which the digital in-phase and quadrature test signals are composed.

11. The method according to claim 10, further comprising, prior to the step of generating:

determining second correction factors from the one or more respective component digital test signals so that the second correction factors correspond to the one or more respective frequencies.

12. The method according to claim 10, where in the steps of generating and determining rely on signal power measurements of, and estimates of a statistical relationship between, the in-phase and quadrature digital signals for all frequencies and the digital in-phase and quadrature test signals separately at one or more frequencies at which the digital in-phase and quadrature test signals are composed.

13. The method according to claim 11, further comprising:

correcting for frequency dependent magnitude and frequency dependent phase imbalances using at least some of the second correction factors.

14. The method according to claim 13, wherein the step of correcting is performed prior to the step of generating.

15. The method according to claim 13, wherein the step of correcting is performed at least partially simultaneously with the step of generating.

16. The method according to claim 13, wherein the step of correcting uses a time domain compensation filter that is programmed using at least some of the second correction factors.

17. The method according to claim 13, wherein the step of correcting uses frequency domain compensation based on the second correction factors.

18. A method of calibrating and compensating for magnitude and phase imbalances in a quadrature receiver, comprising the steps of:

generating first correction factors from in-phase and quadrature digital signals, the signals being derived from a received signal, the received signal being other than a signal received solely for the purposes of calibration; and

compensating for one or more of frequency dependent magnitude imbalance and frequency dependent phase imbalance using at least some of the first correction factors.

19. The method according to claim 18, wherein the received signal comprises a received modulated signal.

20. The method according to claim 18, wherein the calibrating and compensating for magnitude and phase imbalances is performed without the use of a specifically configured I/Q calibration signal but rather by examining regularly received signals that carry data.

21. The method according to claim 18, further comprising, prior to the step of generating:

performing analog to digital conversion on respective in-phase and quadrature analog signals along respective in-phase and quadrature signal paths to form the in-phase and quadrature digital signals, the in-phase and quadrature analog signals being derived from the received signal.

22. The method according to claim 21, wherein the received signal comprises an analog signal received at an antenna of the quadrature receiver in a wireless communications system.

23. The method according to claim 21, wherein the received signal comprises an analog signal received at the quadrature receiver in a wireline communications system.

24. A method of calibrating and compensating for magnitude and phase imbalances in a quadrature receiver, comprising the steps of:

generating first and second correction factors from in-phase and quadrature digital signals, the signals being derived from a received signal, the received signal being other than a signal received solely for the purposes of calibration, the first correction factors being generated following an initial calibration period during which the in-phase and quadrature digital signals are configured to have approximately equal phase; and

compensating for one or more of frequency independent magnitude imbalance, frequency independent phase imbalance, frequency dependent magnitude imbalance, and frequency dependent phase imbalance using the first and second correction factors.

25. The method according to claim 24, wherein the received signal comprises a received modulated signal.

26. A method according to claim 24, wherein the step of generating further comprises:

basing the second correction factors at least in part on the first correction factors.

27. A method according to claim 24, wherein the first correction factors measure frequency dependent phase and magnitude imbalances arising from the different in-phase and quadrature signal paths of the quadrature receiver.

28. A method according to claim 24, wherein the second correction factors measure frequency independent magnitude imbalances arising from differences in-phase and quadrature signal paths of the quadrature receiver.

29. A method according to claim 24, wherein the second correction factors measure frequency independent phase imbalances arising from a correlation in the digital in-phase and quadrature test signals.

30. A method of calibrating magnitude and phase imbalances in a quadrature receiver, comprising the steps of:

performing statistical calibration of in-phase and quadrature digital signals over the full frequency range of the signals and at one or more separate frequencies of interest at which the in-phase and quadrature digital signals are composed, the signals being derived from a received signal, the received signal being other than a signal received solely for the purposes of calibration; and

generating phase and magnitude imbalance correction factors based on the statistical calibration.

31. The method according to claim 30, wherein the received signal comprises a received modulated signal.

32. A method according to claim 30, further comprising the step of:

compensating for one or more of frequency independent magnitude imbalance, frequency independent phase imbalance, frequency dependent magnitude imbalance, and frequency dependent phase imbalance using the phase and magnitude imbalance correction factors.

33. A method according to claim 30, wherein the step of performing statistical calibration further comprises:

comparing the respective signal power of the in-phase and quadrature digital signals with one another.

34. A method according to claim 30, wherein the step of performing statistical calibration further comprises:

determining the degree to which the in-phase and quadrature digital signals are correlated with one another.

35. A method according to claim 30, wherein the step of performing statistical calibration is performed for an initial number of signal samples.

36. A method according to claim 30, wherein the step of performing statistical calibration is performed continuously to provide ongoing iterative and adaptive compensation for frequency independent and dependent magnitude and phase imbalances using the phase and magnitude imbalance correction factors.