Receiver for correcting frequency dependent I/Q phase error

• US 20050008107A1
• Filed: 07/10/2003
• Published: 01/13/2005
• Est. Priority Date: 07/10/2003
• Status: Abandoned Application

• Current Assignee: Radia Communications, Inc. (Texas Instruments, Inc.)
• Original Assignee: Radia Communications, Inc. (Texas Instruments, Inc.)
• Inventors: Brown, James E. C.
• Application Number:
  US10/617,281
• Publication Number:
  US 20050008107A1
• Time in Patent Office: Days
• US Class Current: 375/343
• CPC Class Codes: H04L 2027/0016 Stabilisation of local oscillators
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal

Abstract

A signal receiver and a method for correcting frequency dependent IQ phase errors. The receiver uses a calibration tone generator for generating a calibration tone for providing in-phase (I) and quadrature phase (Q) tone components, I and Q filters for filtering the I and Q calibration tone components for issuing filtered I and Q output tones having undesired frequency dependent I/Q phase error, and a correlator for cross correlating the I and Q output tones for providing a correlation feedback signal. At least one of the I and Q filters has at least one adjustable pole and one adjustable zero. The correlation feedback signal adjusts the frequency of the adjustable poles and zeroes for reducing the frequency dependent I/Q phase error.

Claims

1. A signal receiver having calibration for a frequency dependent I/Q phase error, comprising:

a calibration tone generator for generating a calibration tone for providing in-phase (I) and quadrature phase (Q) tone components;

I and q filters for filtering said I and Q calibration tones for issuing filtered I and Q output tones having an undesired frequency dependent I/Q phase error, at least one of the I and Q filters having an adjustable characteristic; and

a correlator for cross correlating said I and Q output tones for providing a cross correlation feedback signal, said correlation feedback signal used for adjusting said adjustable characteristic for reducing said frequency dependent I/Q phase error;

2. The receiver of claim 1, wherein:

said correlation feedback signal adjusts said adjustable characteristic for minimizing a phase difference between said I output tone and said Q output tone.

3. The receiver of claim 1, wherein:

said calibration tone has a frequency near to a cutoff frequency for said I and Q filters.

4. The receiver of claim 1, wherein:

the I and Q filters include an I analog filter for providing said I output tone and a Q analog filter for providing said Q output tone; and

said adjustable characteristic is a cutoff frequency of at least one of said I and Q analog filters.

5. The receiver of claim 4, wherein:

said cutoff frequency is adjusted by frequency scaling at least one pole and at least one zero of said at least one of said I and Q analog filters by a certain common factor.

6. The receiver of claim 4, wherein:

said certain common scale factor is adjusted by adjusting channel resistance of at least one transistor.

7. The receiver of claim 1, wherein:

the I and Q filters include I and Q allpass filters for providing said I and Q output tones; and

said adjustable characteristic is a phase delay of at least one of said I and Q allpass filters.

8. The receiver of claim 7, wherein:

said phase delay is adjusted by frequency scaling at least one pole by a certain factor and frequency scaling at least one zero by an inverse of said certain factor in said at least one of said I and Q allpass filters.

9. The receiver of claim 1, further comprising:

a frequency downconverter including a local oscillator for providing a complex LO signal and I and Q frequency downconverters using said LO signal for downconverting an input signal having a carrier frequency to I and Q signal components; and

wherein;

the calibration tone generator issues a calibration signal as said input signal having a certain frequency offset from said carrier frequency for providing said I and Q calibration tone components in place of said I and Q signal components.

10. A method for correcting frequency dependent I/Q phase error, comprising:

generating a calibration tone for providing in-phase (I) and quadrature phase (Q) tone components;

filtering said I and Q calibration tones for providing filtered I and Q output tones having undesired frequency dependent I/Q phase error;

cross correlating said I and Q output tones for providing a cross correlation feedback signal; and

adjusting an adjustable characteristic of at least one of the I and Q filters with said correlation feedback signal for reducing said frequency dependent I/Q phase error.

11. The method of claim 10, wherein:

the step of adjusting said adjustable characteristic includes minimizing a phase difference between said I output tone and said Q output tone.

12. The method of claim 10, wherein:

said calibration tone has a frequency near to a cutoff frequency for said I and Q filters.

13. The method of claim 10, wherein:

the step of filtering said I and Q calibration tones includes filtering said I calibration tone component with an I analog filter for providing said I output tone; and

filtering said Q calibration tone component with a Q analog filter for providing said Q output tone; and

the step of adjusting said adjustable characteristic includes adjusting a cutoff frequency of at least one of said I and Q analog filters.

14. The method of claim 13, wherein:

the step of adjusting said cutoff frequency includes frequency scaling at least one pole and at least one zero of said at least one of said I and Q analog filters by a certain common factor.

15. The method of claim 13, wherein:

said step of frequency scaling includes adjusting channel resistance of at least one transistor.

16. The method of claim 10, wherein:

the step of filtering said I and Q calibration tone components includes passing the I and Q calibration tones through I and Q allpass filters for providing said I and Q output tones; and

the step of adjusting said adjustable characteristic includes adjusting a phase delay of at least one of said I and Q allpass filters.

17. The method of claim 16, wherein:

the step of adjusting said phase response includes frequency scaling at least one pole by a certain factor and frequency scaling at least one zero by an inverse of said certain factor in said at least one of said I and Q allpass filters.

18. The method of claim 10, further comprising:

frequency downconverting an input signal having a carrier frequency with a complex LO signal to I and Q signal components; and

wherein;

the step of generating said calibration tone includes issuing a calibration signal as said input signal having a certain frequency offset from said carrier frequency for providing said I and Q calibration tone components in place of said I and Q signal components.