Alignment methods and apparatus for I/Q phase and amplitude error correction and image rejection improvement

• US 20020177425A1
• Filed: 03/29/2001
• Published: 11/28/2002
• Est. Priority Date: 03/29/2001
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Li, Frank Xiaohui
• Granted Patent: US 6,760,577 B2
• Time in Patent Office: Days
• US Class Current: 455/296
• CPC Class Codes: H03D 7/18 Modifications of frequency-changers for eliminating image frequencies H03D7/16 takes precedence
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

Alignment methods and apparatus for I/Q phase and amplitude error correction and image rejection improvement that may be used at the time of circuit fabrication or on chip for use during operation. The alignment method may be used to improve the I/Q phase and amplitude accuracy of a direct conversion transceiver or to improve image rejection in an up or downconversion mixer. For alignment purposes, a pilot tone of a selected frequency is used to provide a calibration reference, with adjustments being made in phase and amplitude to drive the I and Q phase and amplitude mismatch toward a minimum.

Claims

1. A method of aligning an I/Q upconverter for minimizing an unwanted sideband comprising:

providing inphase and quadrature signals;

upconverting the inphase and quadrature signals using inphase and quadrature components of a carrier frequency to provide representative wanted and an unwanted sidebands;

downconverting the output of the upconversion and carrier leakage using a pilot tone having a second frequency as the local oscillator of the downconverter, the difference in the first and second frequencies placing the wanted and not the unwanted sideband and carrier leakage as downconverted at frequencies that may be filtered out with a low pass filter;

filtering out the wanted sideband and the carrier leakage; and

,

adjusting the amplitude of at least one of the inphase and quadrature signals and the phase of at least one of the inphase and quadrature components of the carrier frequency to minimize the unwanted sideband.

2. The method of claim 1 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and at least one of the carrier frequency and the pilot tone is generated using a fractional N phase locked loop.

3. The method of claim 1 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the carrier frequency is generated using a fractional N phase locked loop.

4. The method of claim 1 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the pilot tone is generated using a fractional N phase locked loop.

5. The method of claim 1 wherein the adjusting is done by laser trimming at the time of integrated circuit manufacture.

6. The method of claim 1 wherein the amplitude and phase adjustments are made electronically during the upconverter I/Q mismatch calibration.

7. The method of claim 1 wherein the amplitude and phase adjustments are made iteratively.

8. The method of claim 1 wherein the carrier is an RF carrier.

9. The method of claim 1 wherein the inphase and quadrature signals are baseband or intermediate frequency sinusoidal signals.

10. The method of claim 9 wherein the difference in the first and second frequencies place the unwanted sideband at a low frequency close to DC and the wanted sideband and carrier leakage are filtered out using a low pass filter.

11. The method of claim 10 wherein the amplitude of at least one of the inphase and quadrature signals and the phase of at least one of the inphase and quadrature components of a carrier frequency are adjusted to minimize the power in the unwanted sideband.

12. The method of claim 11 wherein the carrier is an RF carrier.

13. The method of claim 9 wherein the inphase and quadrature signals are provided by providing an intermediate frequency sinusoidal signal to a quadrature divider.

14. The method of claim 13 wherein the difference in the first and second frequencies place the unwanted sideband at a low frequency close to DC and the wanted sideband and carrier leakage are filtered out using a low pass filter.

15. The method of claim 14 wherein the amplitude of at least one of the inphase and quadrature signals and the phase of at least one of the inphase and quadrature components of a carrier frequency are adjusted to minimize the power in the unwanted sideband.

16. The method of claim 15 wherein the carrier is an RF carrier.

18. The apparatus of claim 17 further including phase-locked loops generating the carrier frequency and the pilot tone from a common reference frequency, at least one of the phase-locked loops being a fractional N phase-locked loop.

19. The apparatus of claim 17 further including phase-locked loops generating the carrier frequency and the pilot tone from a common reference frequency, the phase-locked loop generating the carrier frequency being a fractional N phase-locked loop.

20. The apparatus of claim 17 further including phase-locked loops generating the carrier frequency and the pilot tone from a common reference frequency, the phase-locked loop generating the pilot tone being a fractional N phase-locked loop.

21. The apparatus of claim 17 wherein the filter is a low pass filter.

22. The apparatus of claim 17 wherein circuitry to sense the unwanted sideband in the output of the low pass filter comprises circuitry to sense the power in the output of the low pass filter.

23. The apparatus of claim 17 further comprising a quadrature divider generating the inphase and quadrature components of the intermediate frequency signal.

24. The apparatus of claim 23 wherein the filter is a low pass filter.

25. The apparatus of claim 23 wherein circuitry to sense the unwanted sideband in the output of the low pass filter comprises circuitry to sense the power in the output of the low pass filter.

27. The apparatus of claim 26 further comprised of phase-locked loops generating the carrier frequency from a common reference frequency, at least one of the phase-locked loops being a fractional N phase-locked loop.

28. The apparatus of claim 26 further comprised of phase-locked loops generating the carrier frequency from a common reference frequency, the phase-locked loop generating the carrier frequency being a fractional N phase-locked loop.

29. The apparatus of claim 26 further comprised of phase-locked loops generating the carrier frequency from a common reference frequency, the phase-locked loop generating the pilot tone being a fractional N phase-locked loop.

30. The apparatus of claim 26 wherein the filter means is a low pass filter means.

31. The apparatus of claim 26 wherein means for sensing the unwanted sideband in the output of the low pass filter means comprises means for sensing the power in the output of the low pass filter means.

32. The apparatus of claim 26 further comprising a quadrature divider means for generating the inphase and quadrature components of the intermediate frequency signal.

33. The apparatus of claim 32 wherein the filter means is a low pass filter means.

34. The apparatus of claim 32 wherein the means for sensing the unwanted sideband in the output of the low pass filter means comprises means for sensing the power in the output of the low pass filter means.

36. The method of claim 35 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and at least one of the carrier frequency and the pilot tone is generated using a fractional N phase locked loop.

37. The method of claim 35 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the carrier frequency is generated using a fractional N phase locked loop.

38. The method of claim 35 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the pilot tone is generated using a fractional N phase locked loop.

39. The method of claim 35 wherein the adjusting is done by laser trimming at the time of integrated circuit manufacture.

40. The method of claim 35 wherein the amplitude and phase adjustments are made electronically during the downconverter I/Q mismatch calibration.

41. The method of claim 35 wherein the amplitude and phase adjustments are made iteratively.

42. The method of claim 35 wherein the pilot tone is a sinusoidal signal.

43. The method of claim 35 wherein the carrier is an RF carrier.

17. Apparatus for aligning an upconverter for receiving inphase and quadrature components of a signal and upconverting the inphase and quadrature components of the signal using inphase and quadrature components of a carrier frequency to provide a wanted sideband comprising:

an amplitude adjust circuit for adjusting the amplitude of at least one of the inphase and quadrature components of the signal;

a phase adjust circuit for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

a pilot tone generator for generating a pilot tone having a frequency having a predetermined relationship with the frequency of the carrier;

a downconverter for downconverting the output of the upconverter using the pilot tone as its local oscillator, the difference in the pilot tone frequency and the carrier frequency placing the wanted and not the unwanted sideband and carrier leakage as downconverted at a frequency that may be filtered out;

a filter for filtering out the wanted sideband and carrier leakage from the output of the downconverter; and

,

circuitry to sense the unwanted sideband in the output of the filter;

whereby the amplitude adjust and the phase adjust circuits may be adjusted to minimize the unwanted sideband in the output of the filter.

26. Apparatus for aligning an upconverter for receiving inphase and quadrature components of a signal and upconverting the inphase and quadrature components of the signal using inphase and quadrature components of a carrier frequency to provide a wanted sideband comprising:

amplitude adjust means for adjusting the amplitude of at least one of the inphase and quadrature components of the signal;

phase adjust means for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

pilot tone generating means for generating a pilot tone having a frequency having a predetermined relationship with the frequency of the carrier;

downconversion means for downconverting the output of the upconverter using the pilot tone, the difference in the pilot tone frequency and the carrier frequency placing the wanted and not the unwanted sideband and carrier leakage as downconverted at frequencies that may be filtered out;

filter means for filtering out the wanted sideband and carrier leakage from the output of the downconversion means; and

,

means for sensing the unwanted sideband in the output of the filter means;

whereby the amplitude adjust and the phase adjust means may be adjusted to minimize the unwanted sideband in the output of the filter means.

35. A method of aligning an I/Q downconverter, the downconverter to recover the inphase and quadrature components of a baseband frequency signal in a desired sideband of a signal input to the downconverter using inphase and quadrature components of a carrier signal, comprising:

injecting a pilot tone into the input of the downconverter, the pilot tone having a frequency which on downconversion, provides inphase and quadrature signals at the baseband frequency; and

,

adjusting the amplitude of at least one of the inphase and quadrature signals and the phase of at least one of the inphase and quadrature components of the carrier frequency to minimize the difference in the amplitudes of the inphase and quadrature signals and to minimize the non-orthogonality of the inphase and quadrature signals.

44. A method of aligning an image rejection mixer downconverter, the downconverter to produce the inphase and quadrature components of an intermediate frequency signal by injecting an image signal at the downconverted input using inphase and quadrature components of a carrier signal, comprising:

injecting a pilot tone into the input of the downconverter in the image band, the pilot tone having a frequency which on downconversion, provides inphase and quadrature signals at the intermediate frequency;

combining the inphase and quadrature signals with a quadrature combiner; and

,

adjusting the amplitude of at least one of the inphase and quadrature signals and the phase of at least one of the inphase and quadrature components of the carrier frequency to minimize the output of the quadrature converter.

45. The method of claim 44 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and at least one of the carrier frequency and the pilot tone is generated using a fractional N phase locked loop.

46. The method of claim 44 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the carrier frequency is generated using a fractional N phase locked loop.

47. The method of claim 44 wherein the carrier frequency and the pilot tone are generated from a common reference frequency, and the pilot tone is generated using a fractional N phase locked loop.

48. The method of claim 44 wherein the adjusting is done by laser trimming at the time of integrated circuit manufacture.

49. The method of claim 44 wherein the amplitude and phase adjustments are made electronically during the downconverter I/Q mismatch calibration.

50. The method of claim 44 wherein the amplitude and phase adjustments are made iteratively.

51. The method of claim 44 wherein the pilot tone is a sinusoidal signal.

52. The method of claim 44 wherein the carrier is an RF carrier.

53. Apparatus for aligning an I/Q downconverter, the downconverter to recover the inphase and quadrature components of a baseband frequency signal in a desired sideband of a signal input to the downconverter using inphase and quadrature components of a carrier signal, comprising:

circuitry for generating a pilot tone which is different in frequency from the carrier frequency to generate baseband signals;

circuitry for injecting a pilot tone into the input of the downconverter to provide inphase and quadrature signals at the baseband frequency;

amplitude adjust circuitry for adjusting the amplitude of at least one of the inphase and quadrature signals; and

,

phase adjust circuitry for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

whereby the difference in the amplitudes of the inphase and quadrature signals may be minimized and the non-orthogonality of the inphase and quadrature signals may be minimized.

54. The apparatus of claim 53 further including circuitry for generating the carrier frequency, wherein the circuitry for generating the pilot tone and the carrier frequency utilizes a common reference frequency and includes at least one fractional N phase-locked loop.

55. The apparatus of claim 53 further including circuitry for generating the carrier frequency, wherein the circuitry for generating the pilot tone and the carrier frequency utilizes a common reference frequency, and the circuitry for generating the pilot tone comprises a fractional N phase-locked loop.

57. The apparatus of claim 56 further including circuitry for generating the carrier frequency, wherein the circuitry for generating the pilot tone and the carrier frequency utilizes a common reference frequency and includes at least one fractional N phase-locked loop.

58. The apparatus of claim 56 further including circuitry for generating the carrier frequency, wherein the circuitry for generating the pilot tone and for generating the carrier frequency utilizes a common reference frequency, and the circuitry for generating the carrier frequency comprises a fractional N phase-locked loop.

59. The apparatus of claim 56 further including circuitry for generating the carrier frequency, wherein the circuitry for generating the pilot tone and for generating the carrier frequency utilizes a common reference frequency, and the circuitry for generating the pilot tone comprises a fractional N phase-locked loop.

56. Apparatus for aligning an image rejection mixer downconverter, the downconverter to produce the inphase and quadrature components of an intermediate frequency signal by injecting an image signal at the downconverted input using inphase and quadrature components of a carrier signal, comprising:

circuitry for generating a pilot tone which is different in frequency from the carrier frequency and in the image band to generate intermediate frequency signals;

circuitry for injecting a pilot tone in the image band into the input of the downconverter to provide inphase and quadrature signals at the intermediate frequency;

circuitry for quadrature combining the inphase and quadrature signals to provide a combined signal due to I/Q mismatch;

amplitude adjust circuitry for adjusting the amplitude of at least one of the inphase and quadrature signals; and

,

phase adjust circuitry for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

whereby the combined signal may be minimized.

60. Apparatus for aligning an I/Q downconverter, the downconverter to recover the inphase and quadrature components of a baseband frequency signal in a desired sideband of a signal input to the downconverter using inphase and quadrature components of a carrier signal, comprising:

means for generating a pilot tone which is different in frequency from the carrier frequency to generate baseband signals;

means for injecting a pilot tone into the input of the downconverter to provide inphase and quadrature signals at the baseband frequency;

amplitude adjust means for adjusting the amplitude of at least one of the inphase and quadrature signals; and

,

phase adjust means for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

whereby the difference in the amplitudes of the inphase and quadrature signals may be minimized and the non-orthogonality of the inphase and quadrature signals may be minimized.

61. The apparatus of claim 60 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency and includes at least one fractional N phase-locked loop.

62. The apparatus of claim 60 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency, and the means for generating the carrier frequency comprises a fractional N phase-locked loop.

63. The apparatus of claim 60 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency, and the means for generating the pilot tone comprises a fractional N phase-locked loop.

64. Apparatus for aligning an image rejection mixer downconverter, the downconverter to produce the inphase and quadrature components of an intermediate frequency signal by injecting an image signal at the downconverted input using inphase and quadrature components of a carrier signal, comprising:

means for generating a pilot tone which is different in frequency from the carrier frequency in the image band to generate intermediate frequency signals;

means for injecting a pilot tone into the input of the downconverter to provide inphase and quadrature signals at the intermediate frequency;

means for quadrature combining the inphase and quadrature signals to provide a combined signal due to I/Q mismatch;

amplitude adjust means for adjusting the amplitude of at least one of the inphase and quadrature signals; and

,

phase adjust means for adjusting the phase of at least one of the inphase and quadrature components of the carrier;

whereby the combined signal may be minimized.

65. The apparatus of claim 64 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency and includes at least one fractional N phase-locked loop.

66. The apparatus of claim 64 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency, and the means for generating the carrier frequency comprises a fractional N phase-locked loop.

67. The apparatus of claim 64 further including means for generating the carrier frequency, wherein the means for generating the pilot tone and the means for generating the carrier frequency utilize a common reference frequency, and the means for generating the pilot tone comprises a fractional N phase-locked loop.