Automatic burst mode I/Q gain and I/Q phase calibration using packet based-fixed correction coefficients

• US 20040146121A1
• Filed: 08/07/2003
• Published: 07/29/2004
• Est. Priority Date: 01/24/2003
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Brown, James E. C., Rothenberg, Bret
• Granted Patent: US 6,940,930 B2
• Time in Patent Office: Days
• US Class Current: 375/322
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal

Abstract

A method and apparatus for balancing I/Q gain and I/Q phase in a signal receiver. The receiver includes an IQ coefficient calculator and an IQ balancer. The IQ coefficient calculator computes a set of correction coefficients for each packet from the I and Q signals in an IQ measurement section at the front of the packet. The IQ balancer uses the correction coefficients for correcting the I/Q gain and I/Q phase errors on a packet-by-packet basis. Optionally, delay devices delay the I and Q signals so that the correction coefficients may be applied to the entire packet, or the portion of the packet in the IQ measurement section is passed through uncorrected and the correction coefficients are applied to the packet after the IQ measurement section.

Claims

1. A method for automatic I/Q balancing for packets of an incoming signal, comprising:

resolving said incoming signal into I and Q signals;

computing packet-fixed correction coefficients from said I and Q signals during a measurement section for a packet; and

correcting at least one of I/Q gain and I/Q phase of said I and Q signals with said packet-fixed correction coefficients for providing corrected said I and Q signals for said packet.

2. The method of claim 1, further comprising:

delaying said I and Q signals by at least said measurement section; and

wherein the step of correcting includes correcting said at least one of said I/Q gain and said I/Q phase of said delayed I and Q signals with said packet-fixed correction coefficients for providing said corrected I and Q signals.

3. The method of claim 2, further comprising:

detecting pre-delay averages for said I and Q signals for a time period not greater than said measurement section before the step of delaying said I and Q signals; and

using said pre-delay averages for reducing DC offset from said delayed I and Q signals before the step of correcting said I and Q signals.

4. The method of claim 1, wherein:

the step of correcting includes using said packet-fixed correction coefficients for correcting said at least one of said I/Q gain and said I/Q phase for a portion of said packet only after said measurement section of said packet for providing said corrected I and Q signals.

5. The method of claim 4, further comprising:

detecting averages for said I and Q signals for a time period not greater than said measurement section; and

using said averages for reducing DC offset of said I and Q signals for a time period of said packet after said measurement section before the step of correcting said I and Q signals.

6. The method of claim 1, wherein:

the step of correcting said at least one of said I/Q gain and said I/Q phase is performed only after the step of computing said packet-fixed correction coefficients.

7. The method of claim 1, wherein:

the step of computing packet-fixed correction coefficients includes computing first and second correction coefficients using a finite number of indexed I values for said I signal and said finite number of indexed Q values for said Q signal;

where

a first term includes a cross correlation of said I values and said Q values;

a second term includes an autocorrelation of said Q values;

a third term includes said first term divided by said second term;

a fourth term includes a sum of absolute values of said Q values;

a fifth term includes a sum of absolute values of a difference of said I values minus a product of said Q values times said third term; and

said first correction coefficient includes said fourth term divided by said fifth term.

8. The method of claim 7, wherein:

said second correction coefficient includes the negative of said third term.

9. The method of claim 7, wherein:

said second correction coefficient includes a negative of a product of said first correction coefficient and said third term.

10. The method of claim 1, further comprising:

demodulating said corrected I and Q signals for estimating data carried on said incoming signal.

11. A signal receiver having automatic I/Q balancing for packets of an incoming signal, comprising:

a quadrature converter for resolving said incoming signal into I and Q signals;

an IQ coefficient calculator for computing packet-fixed correction coefficients from said I and Q signals during a measurement section of a packet; and

an IQ balancer for using said packet-fixed correction coefficients for correcting at least one of I/Q gain and I/Q phase of said I and Q signals for providing corrected said I and Q signals for said packet.

12. The receiver of claim 11, further comprising:

I and Q delay devices for delaying said I and Q signals by at least said measurement section; and

wherein;

the step of correcting includes correcting said at least one of said I/Q gain and said I/Q phase of said delayed I and Q signals with said packet-fixed correction coefficients for providing said corrected I and Q signals.

13. The receiver of claim 12, further comprising:

an average detector for detecting pre-delay averages for said I and Q signals for a time period not greater than said measurement section before the step of delaying said I and Q signals; and

an average corrector for using said pre-delay averages for reducing DC offset from said delayed I and Q signals before the step of correcting said I and Q signals.

14. The receiver of claim 11, wherein:

the IQ balancer uses said packet-fixed correction coefficients for correcting said at least one of said I/Q gain and said I/Q phase of said I and Q signals for a time period of said packet only after said measurement section for providing said corrected I and Q signals.

15. The receiver of claim 14, further comprising:

an average detector for detecting averages for said I and Q signals for a time period not greater than said measurement section; and

an average corrector for using said averages for reducing DC offset of said I and Q signals for a time period of said packet after said measurement section before the step of correcting said I and Q signals.

16. The receiver of claim 11, wherein:

the IQ balancer corrects said at least one of said I/Q gain and I/Q phase only after the IQ coefficient calculator calculates said packet-fixed correction coefficients.

17. The receiver of claim 11, wherein:

the IQ coefficient calculator computes first and second said correction coefficients using a finite number of indexed I values for said I signal and said finite number of indexed Q values for said Q signal;

where

a first term includes a cross correlation of said I values and said Q values;

a second term includes an autocorrelation of said Q values;

a third term includes said first term divided by said second term;

a fourth term includes a sum of absolute values of said Q values;

a fifth term includes a sum of absolute values of a difference of said I values minus a product of said Q values times said third term; and

said first correction coefficient includes said fourth term divided by said fifth term.

18. The receiver of claim 17, wherein:

said second correction coefficient includes the negative of said third term.

19. The receiver of claim 17, wherein:

said second correction coefficient includes a negative of a product of said first correction coefficient and said third term.

20. The receiver of claim 11, further comprising:

a digital IQ signal receiver for demodulating said corrected I and Q signals for estimating data carried on said incoming signal.