Simplified high frequency tuner and tuning method

• US 7,116,963 B2
• Filed: 08/25/2003
• Issued: 10/03/2006
• Est. Priority Date: 09/13/1996
• Status: Expired due to Fees

• Current Assignee: Washington Research Foundation (University of Washington)
• Original Assignee: University of Washington
• Inventors: Suominen, Edwin A.
• Primary Examiner(s): Eng, George
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US10/649,305
• Publication Number:
  US 20040038655A1
• Time in Patent Office: 1,135 Days
• Field of Search: 455/142, 455/143, 455/207, 455/302, 455/303, 455/305, 455/306, 455/316, 455/324, 455/338, 455/214, 455/213, 455/286, 455/299, 455/150.1, 455/182.1, 455/182.3, 455/183.1, 455/339, 375/322, 375/324
• US Class Current: 455/302
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H04B 1/06 Receivers
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178

Abstract

A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Claims

1. A tuning method comprising:

(a) mixing a channel of interest from a channelized spectrum having a predetermined channel spacing with a first local oscillator signal;

(b) mixing the channel of interest with a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal;

(c) wherein the first local oscillator signal has a first frequency that is (1) one-half of a channel spacing displaced from an integer multiple of the channel spacing, and (2) selected to frequency translate the channel of interest to within a passband whose lower edge is spaced from DC by about the channel spacing and whose width is about the channel spacing;

(d) the channel of interest has a predetermined maximum bandwidth less than the channel spacing;

(e) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest; and

(f) the method further comprises providing spectrum coverage within one of the high frequency spectra of interest and not the other.

2. The method of claim 1 further comprising coarse-tuning the local oscillator signal by one local oscillator step from the first frequency to a second frequency an integral number of channel spacings from the first frequency.

3. A tuning method of claim 1 further comprising

(a) mixing a channel of interest from a channelized spectrum having a predetermined channel spacing with a first local oscillator signal:

(b) mixing the channel of interest with a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal;

(c) wherein the first local oscillator signal has a first frequency that is (1) one-half of a channel spacing displaced from an integer multiple of the channel spacing, and (2) selected to frequency translate the channel of interest to within a passband whose lower edge is spaced from DC by about the channel spacing and whose width is about the channel spacing.

4. A tuning method comprising:

(a) mixing a channel of interest from a channelized spectrum having a predetermined channel spacing with a first local oscillator signal;

(b) wherein the first local oscillator signal has a first frequency that is (1) one-half of a channel spacing displaced from an integer multiple of the channel spacing, and (2) selected to frequency translate the channel of interest to within a passband whose lower edge is spaced from DC by about the channel spacing and whose width is about the channel spacing;

(c) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest; and

(d) the method further comprises providing spectrum coverage within one of the high frequency spectra of interest and not the other.

5. The method of claim 4 further comprising switching between:

(a) providing spectrum coverage within the lower high frequency spectrum of interest and not the upper high frequency spectrum of interest; and

(b) providing spectrum coverage within the upper high frequency spectrum of interest and not the lower high frequency spectrum of interest.

6. Apparatus turning, from a channelized spectrum having a predetermined channel spacing, a channel of interest, the apparatus comprising:

(a) a local oscillator configured to generate a local oscillator signal at a first frequency that is one-half of the channel spacing displaced from an integer multiple of the channel spacing; and

(b) a mixer responsive to the local oscillator signal and the channel of interest, wherein the mixer frequency translates the channel of interest;

(c) a second local oscillator configured to generate a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal; and

(d) a second mixer responsive to the second local oscillator signal and the channel of interest, wherein (1) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest, and (2) the apparatus provides spectrum coverage within one of the high frequency spectra of interest and not the other;

(e) the frequency-translated channel of interest falls within a passband that is about a channel spacing wide and that is spaced from DC by a frequency offset of about the channel spacing; and

(f) the channel of interest has a predetermined maximum bandwidth less than the channel spacing.

7. Apparatus for tuning, from a channelized spectrum having a predetermined channel spacing, a channel of interest, the apparatus comprising:

(a) a local oscillator configured to generate a local oscillator signal at a first frequency that is one-half of the channel spacing displaced from an integer multiple of the channel spacing;

(b) a mixer responsive to the local oscillator signal and the channel of interest, wherein the mixer frequency translates the channel of interest; and

(c) a second local oscillator configured to generate a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal;

(d) wherein the frequency-translated channel of interest falls within a passband that is about a channel spacing wide and that is spaced from DC by a frequency offset of about the channel spacing.

8. The apparatus of claim 7 further comprising a second mixer responsive to the second local oscillator signal and the channel of interest, wherein:

(a) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest; and

(b) the apparatus provides spectrum coverage within one of the high frequency spectra of interest and not the other.

9. Apparatus for tuning, from a channelized spectrum having a predetermined channel spacing, a channel of interest, the apparatus comprising:

(a) a local oscillator configured to generate a first local oscillator signal at a first frequency that is an integer multiple of the channel spacing and a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal; and

(b) a pair of mixers, each responsive to (1) a respective one of the local oscillator signals and (2) the channel of interest, wherein the mixers frequency translate the channel of interest;

(c) wherein the frequency-translated channel of interest falls within a near-baseband passband spaced from DC by a frequency offset of at least about the channel spacing.

10. The apparatus of claim 9 wherein the spacing of the lower edge of the near-baseband passband from DC is greater than the channel spacing.

11. The apparatus of claim 10 wherein the spacing of the lower edge of the near-baseband passband from DC is about twice the channel spacing.

12. The apparatus of claim 9 wherein:

(a) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest; and

(b) the apparatus provides spectrum coverage within one of the high frequency spectra of interest and not the other.

48. The apparatus of claim 9 further comprising a digital circuit that substantially rejects the image.

13. A method for tuning a channelized signal of interest from within a channelized spectrum, the method comprising:

(a) splitting an incoming signal into two signal paths;

(b) generating an approximately quadrature local oscillator signal from a local oscillator that is coarse-tunable across the channelized spectrum with a step size that is an integer multiple of the channel spacing;

(c) quadrature mixing the split incoming signal with the local oscillator signal, thereby;

(1) frequency translating to a near-baseband passband an upper high frequency spectrum of interest from above the frequency of the local oscillator signal and a lower high frequency spectrum of interest from below the frequency of the local oscillator signal, the near-baseband passband being spaced from DC by at least about the channel spacing; and

(2) producing I and Q signals in approximate quadrature relation;

(d) limiting the frequency spectrum of the I and Q signals, wherein spectrum coverage is provided of a selected one of the high frequency spectra of interest and analog processing of signals at or close to DC is avoided; and

(e) repeating (a) through (d) in turn for a plurality of local oscillator frequencies, wherein high frequency spectra of interest tunable with the local oscillator frequencies of the plurality are interspersed among local oscillator frequencies of the plurality within the channelized spectrum.

14. The method of claim 13 wherein the near-baseband passband is sized to fit one channel spacing.

15. The method of claim 13 further comprising providing spectrum coverage within one of the high frequency spectra of interest and not the other.

16. The method of claim 13 wherein the spacing of the lower edge of the near-baseband passband from DC is greater than the channel spacing.

17. The method of claim 16 wherein the spacing of the lower edge of the near-baseband passband from DC is about twice the channel spacing.

18. The method of claim 13 wherein limiting the frequency spectrum of the I and Q signals comprises filtering the signals in continuous-time using switched-capacitor circuitry.

19. The method of claim 13 wherein the near-baseband passband is defined with reference to a lower frequency F1 and an upper frequency F2, wherein F1=F2−

F1 and F2−

F1 is about an integer multiple of channel spacings.

20. The method of claim 13 wherein limiting the frequency spectrum of the I and Q signals comprises highpass and lowpass filtering the signals in continuous-time.

21. The method of claim 20 wherein limiting the frequency spectrum of the I and Q signals comprises filtering the signals in continuous-time using switched-capacitor circuitry.

22. The method of claim 20 wherein limiting the frequency spectrum of the I and Q signals further comprises filtering the signals in discrete-time.

23. The method of claim 13 further comprising providing spectrum coverage within one of the high frequency spectra of interest and not the other.

24. The method of claim 23 further comprising:

(a) converting the I and Q signals to digital I and Q signals; and

(b) combining the digital I and Q signals to reject an undesired mixing image.

25. The method of claim 24 further comprising correcting amplitude and phase errors between the digital I and Q signals.

35. The method of claim 15 further comprising providing spectrum coverage within the upper high frequency spectrum of interest at one time and providing spectrum coverage within the lower high frequency spectrum of interest at a different time.

26. Apparatus for tuning a channelized signal of interest from within a channelized spectrum having a predetermined channel spacing, the apparatus comprising:

(a) an RF amplifier responsive to an incoming signal;

(b) a local oscillator that is coarse-tunable across the channelized spectrum with a step size that is an integer multiple of the channel spacing to a plurality of local oscillator frequencies;

(c) first and second filters defining a near-baseband passband spaced from DC by about an integer multiple of the channel spacing;

(d) first and second mixers, responsive to an amplified signal from the RF amplifier and an approximately quadrature local oscillator signal from the local oscillator, frequency translating to the near-baseband passband (1) an upper

high frequency spectrum of interest from above the frequency of the local oscillator signal, and (2) a lower high frequency spectrum of interest from below the frequency of the local oscillator signal; and

(e) a selector structured to select one of the high frequency spectra of interest.

27. The apparatus of claim 26 wherein the near-baseband passband is sized to fit one channel spacing.

28. The apparatus of claim 26 wherein the spacing of the lower edge of the near-baseband passband from DC is about twice the channel spacing.

29. The apparatus of claim 26 wherein the filters include continuous time switched-capacitor circuitry.

30. The apparatus of claim 26 wherein the near-baseband passband is spaced from DC by about the channel spacing and is about an integer multiple of the channel spacing wide.

31. The apparatus of claim 30 wherein the spacing of the lower edge of the near-baseband passband from DC is about twice the channel spacing.

32. The apparatus of claim 26 wherein the filters include continuous-time highpass and lowpass filters.

33. The apparatus of claim 32 wherein the filters further include continuous-time switched-capacitor circuitry.

34. The apparatus of claim 26 further comprising discrete-time filters.

36. A tuning method comprising:

(a) mixing a channel of interest from a channelized spectrum with a first local oscillator signal;

(b) filtering the mixed signal to define a near-baseband passband that is (1) sized to fit one channel spacing, and (2) has a lower edge spaced from DC by about an integer multiple of the channel spacing or a half-channel-spacing displaced from about an integer multiple of the channel spacing;

(c) splitting the incoming signal into two signal paths; and

(d) quadrature mixing the split incoming signal with the first local oscillator signal and a second local oscillator signal approximately in quadrature with the first local oscillator signal.

37. The method of claim 36 further comprising performing digital image rejection.

38. The method of claim 36 further comprising performing the image rejection after the quadrature mixing.

39. The method of claim 38 wherein the lower edge of the near-baseband passband is spaced from DC by about twice the channel spacing.

40. A method for tuning a channel of interest, comprising:

(a) receiving a channel of interest from a channelized spectrum having a predetermined channel spacing, wherein the channel of interest has a predetermined maximum bandwidth less than the channel spacing;

(b) producing I and Q signals in approximate quadrature relation by mixing the channel with an approximately quadrature local oscillator signal having a first frequency that is an integer multiple of the channel spacing; and

(c) defining a near-baseband passband whose lower edge is spaced from DC by at least about the channel spacing, by passband filtering the I and Q signals.

41. The method of claim 40 further comprising coarse-tuning the local oscillator signal by one local oscillator step from the first frequency to a second frequency an integral number of channel spacings from the first frequency.

42. The method of claim 41 wherein the second frequency is two channel spacings from the first frequency.

43. The method of claim 40 wherein passband filtering the I and Q signals comprises filtering the signals in continuous-time using switched-capacitor circuitry.

44. A method for tuning a channel of interest, comprising:

(a) receiving a channel of interest from a channelized spectrum having a predetermined channel spacing, wherein the channel of interest has a predetermined maximum bandwidth less than the channel spacing;

(b) producing I and Q signals in approximate quadrature relation by mixing the channel of interest with an approximately quadrature local oscillator signal having a first frequency that is one-half of a channel spacing displaced from an integer multiple of the channel spacing; and

(c) defining a near-baseband passband whose lower edge is spaced from DC by an integer multiple of the channel spacing, by passband filtering the I and Q signals.

45. The method of claim 44 further comprising coarse-tuning the local oscillator signal by one local oscillator step from the first frequency to a second frequency an integral number of channel spacings from the first frequency.

46. The method of claim 45 wherein the second frequency is two channel spacings from the first frequency.

47. The method of claim 44 wherein passband filtering the I and Q signals comprises filtering the signals in continuous-time using switched-capacitor circuitry.

49. A method for tuning a channel from a channelized spectrum having predetermined channel spacing, the method comprising:

(a) mixing a channel of interest with a first local oscillator signal;

(b) wherein the first local oscillator signal has a first frequency that (1) is an integer multiple of the channel spacing and (2) is selected to frequency translate the channel of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the channel spacing; and

(c) the method further comprises mixing the channel of interest with a second local oscillator signal having the first frequency and being approximately in quadrature with the first local oscillator signal.

50. A method for tuning a channel from a channelized spectrum having predetermined channel spacing, the method comprising:

(a) mixing a channel of interest with a first local oscillator signal;

(b) wherein the first local oscillator signal has a first frequency that (1) is an integer multiple of the channel spacing and (2) is selected to frequency translate the channel of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the channel spacing;

(c) the channel of interest lies within one of an upper high frequency spectrum of interest and a lower high frequency spectrum of interest; and

(d) the method further comprises providing spectrum coverage within one of the high frequency spectra of interest and not the other.

51. The method of claim 50 further comprising switching between:

(a) providing spectrum coverage within the lower high frequency spectrum of interest and not the upper high frequency spectrum of interest; and

(b) providing spectrum coverage within the upper high frequency spectrum of interest and not the lower high frequency spectrum of interest.

52. A tuning method comprising:

(a) receiving a channel of interest from a channelized spectrum having a predetermined channel spacing;

(b) producing I and Q signals in approximate quadrature relation by mixing the channel of interest with an approximately quadrature local oscillator signal having a frequency that is one of a set of local oscillator frequencies; and

(c) passband filtering the I and Q signals to define a passband whose lower edge is situated near baseband but spaced from DC by at least about the channel spacing.

53. The method of claim 52 wherein the channel of interest has a predetermined maximum bandwidth less than the channel spacing.

54. The method of claim 52 wherein filtering to define the passband comprises defining a passband whose center frequency has a spacing from DC that differs from an integer multiple of channel spacing or a half-channel displaced from an integer multiple of channel spacing by a frequency adjustment.

55. The method of claim 54 wherein the frequency adjustment is about half of the channel spacing.

56. The method of claim 54 wherein filtering to define the passband comprises defining a passband that is approximately a channel spacing wide.

57. The method of claim 56 wherein defining a passband comprises defining a passband that is wider than a channel spacing by a frequency adjustment.

58. The method of claim 54 wherein the frequency adjustment is predetermined.

59. The method of claim 54 wherein the frequency adjustment is static.

60. The method of claim 54 wherein defining a passband comprises defining a passband by extending the upper and lower edges of the passband by frequency adjustments.

61. The method of claim 60 wherein the frequency adjustments are not equal.

62. The method of claim 52 wherein filtering to define the passband comprises determining the edges of the passband by the center frequency of the channel of interest contained in the I and Q signals.

63. The method of claim 62 wherein determining the edges of the passband comprises making the passband wider than the width of the channel of interest by a predetermined frequency adjustment.

64. The method of claim 63 wherein making the passband wider than the width of the channel of interest is done by adjusting both the upper and lower edges of the passband by predetermined frequency adjustments.

65. The method of claim 61 wherein the predetermined frequency adjustments are not equal.

66. The method of claim 61 wherein determining the edges of the passband further comprises separating the edges of the passband by approximately the maximum bandwidth of the channel of interest.

67. The method of claim 66 wherein separating the edges of the passband comprises making the passband wider than the spacing of the channel of interest by a predetermined frequency adjustment.

68. The method of claim 52 wherein the lower edge of the near-baseband passband is spaced from DC by about the channel spacing.

69. The method of claim 52 wherein the lower edge of the passband is spaced from DC by about 1.5 times the channel spacing.

70. The method of claim 52 wherein the lower edge of the passband is spaced from DC by about twice the channel spacing.

71. The method of claim 52 wherein the lower edge of the passband is spaced from DC by about 2.5 times the channel spacing.