I/Q calibration in the presence of phase offset

• US 7,944,984 B1
• Filed: 02/12/2007
• Issued: 05/17/2011
• Est. Priority Date: 04/11/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Salhotra, Atul, Cho, Thomas B., Zhao, Qing, Lou, Hui-Ling, Wu, Songping
• Primary Examiner(s): Liu; Shuwang
• Assistant Examiner(s): TAYONG, HELENE E
• Application Number:
  US11/705,248
• Time in Patent Office: 1,555 Days
• Field of Search: 375/261, 375/343, 375/322, 341/118, 341/119, 341/120, 341/144, 341/155, 455/115.1, 455/126, 455/323
• US Class Current: 375/261
• CPC Class Codes: H04L 27/364 Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels

Abstract

An I/Q calibration system for a quadrature amplitude modulation (QAM) mode transceiver includes a signal generator that generates reference in-phase (I) and quadrature (Q) signals. An I/Q mismatch compensation module generates compensated I and Q signals based on the reference I and Q signals and amplitude and phase correction signals. An I/Q mismatch calibration module generates the amplitude and phase correction signals. A phase stepper module varies a phase of the reference I and Q signals based on the amplitude and phase correction signals.

Claims

1. An in-phase and quadrature (I/O) calibration system for a quadrature amplitude modulation (QAM) mode transceiver, the I/Q calibration system comprising:

a signal generator configured to generate a reference in-phase (I) signal and a reference quadrature (Q) signal;

an I/Q mismatch compensation module configured to generate a compensated I signal and a compensated Q signal based on (i) the reference I signal, (ii) the reference Q signal, (iii) an amplitude correction signal, and (iv) a phase correction signal;

an I/Q mismatch calibration module configured to generate the amplitude correction signal and the phase correction signal; and

a phase stepper module configured to vary a phase of at least one of the reference I signal or the reference Q signal based on (i) the amplitude correction signal and (ii) the phase correction signal.

2. The I/Q calibration system of claim 1, further comprising:

a transmit analog mixer module configured to generate a QAM signal based on (i) the compensated I signal and (ii) the compensated Q signal; and

a receive analog mixer configured to, based on the QAM signal, generate a received I signal and a received Q signal,

wherein the compensated I signal and the compensated Q signal are respectively related to the received I signal and the received Q signal by a phase offset, and

wherein the phase stepper module reduces the phase offset.

3. The I/Q calibration system of claim 2, further comprising an analog-to-digital converter configured to convert the received I signal and the received Q signal from analog formats to respective digital representations,

wherein the I/Q mismatch calibration module is configured to, based on the digital representations, generate the amplitude correction signal and the phase correction signal.

4. The I/Q calibration system of claim 1, wherein the phase stepper module is configured to vary the phase of the at least one of the reference I signal or the reference Q signal when a magnitude of at least one of the amplitude correction signal or the phase correction signal exceeds a predetermined magnitude.

5. The I/Q calibration system of claim 1, wherein the phase stepper module is configured to vary the phase of the at least one of the reference I signal or the reference Q signal based on at least one of the amplitude correction signal or the phase correction signal crossing zero more than a predetermined number of times.

6. The I/Q calibration system of claim 1, wherein the phase stepper module is configured to correct I/Q mismatch of a radio frequency (RF) transmitter by varying the phase of the at least one of the reference I signal or the Q signal based on (i) the amplitude correction signal and (ii) the phase correction signal.

7. The I/Q calibration system of claim 1, wherein the phase stepper module is configured to perform the varying of the phase of the at least one of the reference I signal or the reference Q signal prior to (i) digital to analog conversion of the compensated I signal and the compensated Q signal and (ii) upconversion of the compensated I signal and the compensated Q signal.

8. The I/Q calibration system of claim 1, wherein:

the compensated I signal is a digital I signal; and

the compensated Q signal is a digital Q signal.

9. The I/Q calibration system of claim 1, wherein the phase stepper module is configured to vary the phase of the at least one of the reference I signal and the reference Q signal by varying phase of the signal generator.

10. The I/Q calibration system of claim 1, wherein:

the compensated I signal does not include a Q component; and

the compensated Q signal does not include an I component.

11. The I/Q calibration system of claim 1, wherein:

the I/Q mismatch calibration module is configured to generate the amplitude correction signal and the phase correction signal based on (i) a detected I component and (ii) a detected Q component of a first signal; and

the I/Q calibration system further comprises a mixer configured to generate the first signal based on a detected I component of a signal transmitted between (i) a transmit mixer module and (ii) a receive mixer module.

12. The I/Q calibration system of claim 11, wherein the I/Q mismatch calibration module generates the amplitude correction signal based on (i) an absolute value of the I component and (ii) an absolute value of the Q component.

13. The I/Q calibration system of claim 1, wherein the phase stepper module, when varying the phase of the at least one of the reference I signal and the reference Q signal, varies at least one of

a phase of the reference I signal relative a phase of the reference Q signal;

or

the phase of the reference Q signal relative the phase of the reference I signal.

14. The I/Q calibration system of claim 1, wherein the phase stepper module minimizes effects of phase offset on the amplitude correction signal and the phase correction signal when varying the phase of the at least one of the reference I signal or the reference Q signal.

15. A self-calibrating quadrature amplitude modulation (QAM) mode transceiver comprising:

a transmitter comprising

a generator configured to generate a digitized in-phase (I) signal and a digitized quadrature (Q) signal,

a compensation module configured to generate a compensated I signal and a compensated Q signal based on (i) the digitized I signal, (ii) the digitized Q signal, (iii) the amplitude correction signal, and (iv) the phase correction signal,

a digital-to-analog converter module configured to generate an analog I signal and an analog Q signal based on (i) the compensated I signal and (ii) the compensated Q signal, and

a first analog mixer module configured to generate a radio-frequency (RF) transmit signal based on (i) the analog I signal and (ii) the analog Q signal;

a calibration module configured to generate the amplitude correction signal and the phase correction signal based on an analog I signal component of the RF transmit signal; and

a phase stepper module configured to vary a phase of at least one of the digitized in-phase (I) signal or the digitized quadrature (Q) signal based on the amplitude correction signal and (ii) the phase correction signal.

16. The transceiver of claim 15, further comprising a receiver comprising:

a second analog mixer module configured to generate an I component signal based on the RF transmit signal, wherein the I component signal includes an analog Q crosstalk signal, and wherein the I component signal and the analog Q crosstalk signal are respectively related to the analog I signal and the analog Q signal by a phase offset;

an analog-to-digital converter (ADC) configured to convert the I component signal to a digitized I component signal; and

a digital mixer configured to generate a reconstructed digitized I signal and a digitized Q crosstalk signal based on the digitized I component signal,

wherein the calibration module is configured to generate the amplitude correction signal and the phase correction signal based on (i) the reconstructed digitized I signal and (ii) the digitized Q crosstalk signal, and

wherein the phase stepper module is configured to vary the phase offset by varying the phase of the at least one of the digitized I signal or the digitized Q signal based on (i) the amplitude correction signal and (ii) the phase correction signal.

17. The transceiver of claim 16, wherein the phase stepper module is configured to vary the phase of the at least one of the digitized I signal or the digitized Q signal by a predetermined amount.

18. The transceiver of claim 16, wherein the second analog mixer module is further configured to generate a Q component signal based on the RF transmit signal.

19. The transceiver of claim 16, wherein the receiver further comprises a band-pass filter (BPF) positioned between the second analog mixer module and the ADC.

20. The transceiver of claim 19, further comprising a switch configured to selectively route the I component signal around the BPF.

21. An in-phase and quadrature (I/O) calibration system for a quadrature amplitude modulation (QAM) mode transceiver, the I/Q calibration system comprising:

signal generator means for generating a reference in-phase (I) signal and a reference quadrature (Q) signal;

I/Q mismatch compensation means for generating a compensated I signal and a compensated Q signal based on (i) the reference I signal, (ii) the reference Q signal, (iii) an amplitude correction signal, and (iv) a phase correction signal;

I/Q mismatch calibration means for generating the amplitude correction signal and the phase correction signal; and

phase stepper means for varying a phase of the reference I signal and the reference Q signal based on the amplitude correction signal and the phase correction signal.

22. The I/Q calibration system of claim 21, further comprising:

transmit analog mixer means for generating a QAM signal based on (i) the compensated I signal and (ii) the compensated Q signal; and

receive analog mixer means for generating a received I signal and a received Q signal based on the QAM signal, wherein the compensated I signal and the compensated Q signal are respectively related to the received I signal and the received Q signal by a phase offset, and

wherein the phase stepper means reduces the phase offset.

23. The I/Q calibration system of claim 22, further comprising analog-to-digital converter means for converting the received I signal and the received Q signal from analog formats to respective digital representations,

wherein the I/Q mismatch calibration means generates the amplitude correction signal and the phase correction signal based on the digital representations.

24. The I/Q calibration system of claim 21, wherein the phase stepper means varies the phase of the at least one of the reference I signal or the reference Q signal when the magnitude of at least one of the amplitude correction signal or the phase correction signal exceeds a predetermined magnitude.

25. The I/Q calibration system of claim 21, wherein the phase stepper means varies the phase of the at least one of the reference I signal or the reference Q signal based on at least one of the amplitude correction signal and the phase correction signal crossing zero more than a predetermined number of times.

26. A self-calibrating quadrature amplitude modulation (QAM) mode transceiver comprising:

a transmitter comprising

generator means for generating a digitized in-phase (I) signal and a quadrature (Q) signal

compensation means for generating a compensated I signal and a compensated Q signal based on (i) the digitized I signal, (ii) the digitized Q signal, (iii) an amplitude correction signal, and (iv) a phase correction signal

digital-to-analog converter means for generating an analog I signal and a Q signal based on (i) the compensated I signal and (ii) the compensated Q signal and

first analog mixer means for generating a radio-frequency (RF) transmit signal based on (i) the analog I signal and the analog (ii) Q signal;

calibration means for generating the amplitude correction signal and the phase correction signal based on the analog I signal component of the RF transmit signal; and

phase stepper means for varying a phase of at least one of the digitized in-phase (I) signal or the digitized quadrature (Q) signal based on (i) the amplitude correction signal and (ii) the phase correction signal.

27. The transceiver of claim 26, further comprising a receiver comprising:

second analog mixer means for generating an I component signal based on the RF transmit signal, wherein the I component signal includes an analog Q crosstalk signal, and wherein the I component signal and the Q crosstalk signal are respectively related to the analog I signal and the analog Q signal by a phase offset;

analog-to-digital converter (ADC) means for converting the I component signal to a digitized I component signal; and

digital mixer means for generating a reconstructed digitized I signal and a reconstructed digitized Q crosstalk signal based on the digitized I component signal,

wherein the calibration means generates the amplitude correction signal and the phase correction signal based on (i) the reconstructed digitized I signal and (ii) the reconstructed digitized Q crosstalk signal, and

wherein the phase stepper means varies the phase offset by varying the phase of the at least one of the digitized I signal or the digitized Q signal based on La the amplitude correction signal and (ii) the phase correction signal.

28. The transceiver of claim 27, wherein the phase stepper means varies the phase of the at least one of the digitized I signal or the digitized Q signal by a predetermined amount.

29. The transceiver of claim 27, wherein the second analog mixer means further generates a Q component signal based on the RF transmit signal.

30. The transceiver of claim 27, wherein the receiver further comprises band-pass filter (BPF) means positioned between the second analog mixer means and the ADC.

31. The transceiver of claim 30, further comprising switch means for selectively routing the I component signal around the BPF.

32. A method of calibrating a quadrature amplitude modulation (QAM) mode transceiver, the method comprising:

generating a reference in-phase (I) signal and a reference quadrature (Q) signal via a signal generator;

generating an amplitude correction signal and a phase correction signal via a mismatch calibration module;

generating a compensated I signal and a compensated Q signal via I/Q mismatch compensation module based on (i) the reference I signal (ii) the reference Q signal, (iii) the amplitude correction signal, and (iv) the phase correction signal; and

varying a phase of the at least one of the reference I signal or the reference Q signal via a phase stepper module based on the amplitude correction signal and the phase correction signal.

33. The method of claim 32, further comprising:

generating a QAM signal based on the compensated I signal and the compensated Q signal; and

generating a received I signal and a received Q signal based on the QAM signal, wherein the compensated I signal and the compensated Q signal are respectively related to the received I signal and the received Q signal by a phase offset, and

wherein varying the phase of the at least one of the reference I signal or the reference Q signal reduces the phase offset.

34. The method of claim 33, further comprising:

converting the received I signal and the received Q signal from analog formats to respective digital representations; and

generating the amplitude correction signal and the phase correction signal based on the digital representations.

35. The method of claim 32, further comprising varying the phase of the at least one of the reference I signal and the reference Q signal when a magnitude of at least one of the amplitude correction signalor the phase correction signal exceeds a predetermined magnitude.

36. The method of claim 32, further comprising varying the phase of the at least one of the reference I signal or the reference Q signal based on at least one of the amplitude correction signal or the phase correction signal crossing zero more than a predetermined number of times.

37. A method of calibrating a quadrature amplitude modulation (QAM) mode transceiver, the method comprising:

generating a digitized in-phase (I) signal and a digitized quadrature (Q) signal via a signal generator;

generating an amplitude correction signal and a phase correction signal via I/Q mismatch calibration module based on an analog I signal component of a RF transmit signal;

generating a compensated I signal and a compensated Q signal via I/Q mismatch compensation module based on (i) the digitized I signal, (ii) the digitized Q signal, (iii) the amplitude correction signal, and (iv) the phase correction signal;

generating an analog I signal and an analog Q signal based on (i) the compensated I signal and (ii) the compensated Q signal; and

varying a phase of the at least one of the digitized in-phase (I) signal or the quadrature (Q) signal via a phase stepper module based on (i) the amplitude correction signal and (ii) the phase correction signal.

38. The method of claim 37, further comprising:

generating an I component signal based on the RF transmit signal, wherein the I component signal includes an analog Q crosstalk signal, and wherein the I component signal and the Q crosstalk signal are respectively related to the analog I signal and the Q signal by a phase offset;

converting the I component signal to a digitized I component signal; and

generating a reconstructed digitized I signal and a digitized Q crosstalk signal based on the digitized I component signal;

generating the amplitude correction signal and the phase correction signal based on the reconstructed digitized I signal and the digitized Q crosstalk signal; and

varying the phase of the at least one of the digitized I signal or the digitized Q signal based on the amplitude correction signal and the phase correction signal and thereby varying the phase offset.

39. The method of claim 38, wherein the phase of the at least one of the digitized I signal or the digitized Q signal is varied by a predetermined amount.

40. The method of claim 38, further comprising generating a Q component signal based on the RF transmit signal.

41. The method of claim 38, further comprising band-pass filtering (BPF) the I-component signal.

42. The transceiver of claim 41, further comprising selectively routing the I component signal around the BPF.