Simplified high frequency tuner and tuning method

• US 20060019624A1
• Filed: 06/15/2005
• Published: 01/26/2006
• Est. Priority Date: 09/13/1996
• Status: Active Grant

• Current Assignee: Washington Research Foundation (University of Washington)
• Original Assignee: University of Washington
• Inventors: Suominen, Edwin A.
• Granted Patent: US 7,606,542 B2
• Time in Patent Office: Days
• US Class Current: 455/200.100
• 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) receiving a channel of interest from a channelized spectrum having a predetermined channel spacing;

(b) frequency translating the channel of interest, by mixing with a local oscillator signal having a frequency that is one of a set of local oscillator frequencies, to within a near-baseband passband that has a maximum bandwidth that is about the channel spacing; and

(c) dynamically varying the passband bandwidth.

2. The method of claim 1 wherein varying the passband bandwidth is accomplished by using a digitally controlled variable bandpass filter.

3. The method of claim 1 wherein the passband is varied in real time.

4. The method of claim 1 wherein the passband is varied to follow variations in the channel of interest.

5. The method of claim 1 further comprising further translating the frequency-translated channel of interest to baseband.

6. The method of claim 5 wherein the frequency translation to baseband is done in the digital domain.

7. The method of claim 5 wherein the translation to baseband is done by mixing the frequency-translated channel of interest with a second local oscillator signal that has a frequency that is approximately the center frequency of the frequency-translated channel of interest.

8. The method of claim 7 wherein the translation to baseband of the frequency-translated channel of interest is fine tuned by adjustment of the second local oscillator frequency.

9. The method of claim 5 wherein the translation to baseband is done by mixing the frequency-translated channel of interest with a second local oscillator signal that has a frequency that is approximately the center frequency of the passband.

10. The method of claim 9 wherein the translation to baseband of the frequency-translated channel of interest is fine tuned by adjustment of the second local oscillator frequency.

11. The method of claim 1 wherein the lower edge of the passband is spaced from DC by at least about the channel spacing.

12. The method of claim 11 wherein varying the passband bandwidth is accomplished by using a digitally controlled variable bandpass filter.

13. The method of claim 11 wherein the passband is varied in real time.

14. The method of claim 11 wherein the passband is varied to follow variations in the channel of interest.

15. The method of claim 11 further comprising further translating the frequency-translated channel of interest to baseband.

16. The method of claim 15 wherein the frequency translation to baseband is done in the digital domain.

17. The method of claim 15 wherein the translation to baseband is done by mixing the frequency-translated channel of interest with a second local oscillator signal that has a frequency that is approximately the center frequency of the passband.

18. The method of claim 15 wherein the translation to baseband of the frequency-translated channel of interest is fine tuned by adjustment of the second local oscillator frequency.

19. The method of claim 15 wherein the translation to baseband is done by mixing the frequency-translated channel of interest with a second local oscillator signal that has a frequency that is approximately the center frequency of the frequency-translated channel of interest.

20. The method of claim 19 wherein the translation to baseband of the frequency-translated channel of interest is fine tuned by adjustment of the second local oscillator frequency.

21. A tuning method comprising:

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

(b) frequency translating the channel of interest, by mixing it with a local oscillator signal having a frequency that is one of a set of local oscillator frequencies, to within a passband that is near baseband and the lower edge of which is spaced from DC by at least about the channel spacing and that has a bandwidth that is about the channel spacing plus a fine tuning adjustment; and

(c) fine tuning the channel of interest by passing a selected range of bandpass frequencies.

22. The method of claim 21 wherein the fine tuning is done by digitally controlled variable bandpass filtering.

23. The method of claim 22 wherein the variable bandpass filter bandwidth is smaller than the passband bandwidth and can be placed anywhere within the passband width.

24. The method of claim 21 wherein the passband width is the bandwidth of the channel of interest plus frequency adjustments added to the upper and lower edges of the bandwidth.

25. The method of claim 24 wherein the upper and lower edge frequency adjustments are not equal.

26. A tuning method comprising:

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

(b) frequency translating the channel of interest by mixing it with a local oscillator signal having a frequency that is one of a set of local oscillator frequencies, to within a near-baseband passband that has a bandwidth that is about the channel spacing plus a fine tuning adjustment; and

(c) fine tuning the channel of interest by digitally controlled variable bandpass filtering to pass a selected range of passband frequencies.

27. The method of claim 26 wherein the variable bandpass filtering can select a range of frequencies anywhere within the passband width.

28. The method of claim 26 wherein the lower edge of the near-baseband passband is spaced from DC by at least about the channel spacing.

29. The method of claim 26 wherein the passband width is the channel spacing plus frequencies adjustments added to the upper and lower edges of the channel spacing.

30. The method of claim 29 wherein the upper and lower edge frequency adjustments are not equal.

31. An 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;

(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 filter configured to define a near-baseband passband; and

(d) a variable bandpass filter responsive to control inputs and configured to fine-tune the channel of interest by passing a range of frequencies within the near-baseband passband;

(e) wherein the frequency-translated channel of interest falls within the near-baseband passband.

32. The apparatus of claim 31 wherein the near-baseband passband is spaced from DC by at least about the channel spacing.

33. The apparatus of claim 31 wherein the near-baseband passband has a bandwidth of about the channel spacing.

34. The apparatus of claim 31 wherein the variable bandpass filter bandwidth is less than the bandwidth of the near-baseband passband.

35. The apparatus of claim 31 further comprising a digital controller coupled to the control inputs of the variable bandpass filter.

36. The apparatus of claim 35 wherein the digital controller defines the center frequency of the variable bandpass filter.

37. A tuning method comprising, with a tuning device:

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

(b) frequency translating the channel of interest to a passband that is near-baseband and the lower edge of which is spaced from DC by at least about the channel spacing, by mixing the channel of interest with approximately phase-quadrature local oscillator signals, thereby creating I and Q signals;

(c) sensing the operating temperature of the tuning device; and

(d) using the sensed temperature to correct errors between the I and Q signals.

38. The method of claim 37 wherein correcting errors comprises choosing a correction factor to optimize image rejection.

39. The method of claim 37 wherein the passband bandwidth is about the channel spacing.

40. A tuning method comprising:

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

(b) frequency translating the channel of interest to a passband that is near baseband and the lower edge of which is spaced from DC by at least about the channel spacing, by mixing the channel of interest with approximately phase-quadrature local oscillator signals, thereby creating I and Q signals; and

(c) using information characterizing errors between the I and Q channels of the individual tuning device, which information has been stored within the device upon completion of device manufacture, to correct errors between the I and Q channels.

41. The method of claim 40 wherein the passband bandwidth is about a channel spacing wide.

42. The method of claim 40 wherein the information characterizing errors constitutes correction factors.

43. A method of tuning comprising:

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

(b) frequency translating the channel of interest to a passband that is near-baseband and the lower edge of which is spaced from DC by at least about the channel spacing, by mixing the channel of interest with approximately phase-quadrature local oscillator signals thereby creating I and Q signals; and

(c) continuously detecting and correcting errors between the I and Q channels.

44. The method of claim 43 wherein the passband bandwidth is about the channel spacing wide.

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

(a) a local oscillator configured to generate approximately phase-quadrature local oscillator signals;

(b) a filter configured to define a near-baseband passband;

(c) mixers, each responsive to one of the phase-quadrature local oscillator signals and the signal of interest, that frequency-translate the signal of interest creating I and Q signals that fall within the near-baseband passband; and

(d) an operating-temperature sensor coupled to correct errors between the I and Q signals.

46. The apparatus of claim 45 wherein the near-baseband passband is frequency-spaced from DC by at least about the channel spacing.

47. The apparatus of claim 45 wherein the bandwidth of the near-baseband passband is about a channel spacing.

48. The apparatus of claim 45 wherein the operating-temperature sensor is coupled to generate a correction factor selected to optimize unwanted signal rejection.

49. The apparatus of claim 45 wherein the sensor is coupled to correct errors between the I and Q signals through a digital controller.

50. A method of tuning comprising:

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

(b) mixing the channel of interest with approximately phase-quadrature local oscillator signals, thereby creating I and Q signals;

(c) frequency translating the channel of interest to a near-baseband passband that has a width equal to about the channel spacing plus a fine tuning adjustment;

(d) fine tuning the channel of interest by passing a selected range of passband;

(e) sensing the operating temperature of the tuning device; and

(f) using the sensed temperature to correct errors between the I and Q channels.

51. The method of claim 50 wherein correcting errors comprises choosing one or more correction factors to optimize image rejection.

52. The method of claim 50 wherein the passband is spaced from DC by at least about the channel spacing.

53. The method of claim 50 wherein fine tuning of the channel of interest is done by digitally controlled variable passband filtering.

54. A tuning method comprising, with a tuning device:

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

(b) mixing the channel of interest with approximately phase-quadrature local oscillator signals, thereby creating I and Q channels;

(c) frequency translating the channel of interest to a near-baseband passband that has a width equal to about the channel spacing;

(d) dynamically varying the passband bandwidth;

(e) further translating the frequency-translated channel of interest to baseband by mixing the frequency-translated channel of interest with a second local oscillator signal; and

(f) sensing the operating temperature of the tuning device and using the sensed temperature information to correct errors between the I and Q channels.

55. The method of claim 54 wherein the lower edge of the passband is spaced from DC by at least about the channel spacing.

56. The method of claim 54 wherein the passband is varied to follow variations in the channel of interest.

57. The method of claim 54 wherein the second local oscillator signal has a frequency that is approximately the center frequency of the frequency-translated channel of interest.

58. The method of claim 57 further comprising fine-turning the translation to baseband of the frequency-translated channel of interest by adjusting the second local oscillator frequency.

59. The method of claim 58 wherein the frequency translation to baseband is done in the digital domain.

60. A tuning method comprising:

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

(b) frequency translating the channel of interest by mixing with a local oscillator signal having a frequency that is one of a set of local oscillator frequencies, to within a near-baseband passband that has a bandwidth that is about the channel spacing; and

(c) further translating the frequency-translated channel of interest to baseband by mixing the frequency-translated channel of interest with a second local oscillator signal.

61. The method of claim 60 further comprising fine tuning the translation to baseband of the frequency-translated channel of interest by adjusting the second local oscillator frequency.

62. The method of claim 60 wherein the frequency translation to baseband is done in the digital domain.

63. The method of claim 60 wherein the second local oscillator signal has a frequency that is approximately the center frequency of the frequency-translated channel of interest.

64. The method of claim 60 wherein the second local oscillator signal has a frequency that is approximately the center frequency of the passband.

65. The method of claim 60 wherein the lower edge of the passband is spaced from DC by at least about the channel spacing.

66. The method of claim 65 wherein the second local oscillator signal has a frequency that is approximately the center frequency of the frequency-translated channel of interest.

67. The method of claim 65 wherein the second local oscillator signal has a frequency that is approximately the center frequency of the passband.

68. The method of claim 65 wherein the frequency translation to baseband is done in the digital domain, and further comprising fine tuning the translation to baseband of the frequency-translated channel of interest by adjusting the second local oscillator frequency.

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

(a) a first local oscillator configured to generate a first local oscillator signal;

(b) a filter configured to define a near-baseband passband;

(c) a first mixer, responsive to the first local oscillator signal and the channel of interest, that frequency-translates the channel of interest to within the near-baseband passband;

(d) a variable bandpass filter responsive to control inputs and configured to vary the width of the near-baseband passband; and

(e) a baseband translator configured to translate the frequency-translated channel of interest to baseband.

70. The apparatus of claim 69 further comprising a temperature sensor configured to sense the operating temperature of the apparatus and coupled to use the sensed temperature information to correct errors arising from signal propagation differences.

71. The apparatus of claim 70 wherein the near-baseband passband is about a channel spacing wide.

72. The apparatus of claim 69 wherein the near-baseband passband is about a channel spacing wide.

73. The apparatus of claim 69 wherein the near-baseband passband is spaced from DC by about the channel spacing.

74. The apparatus of claim 69 wherein the baseband translator comprises:

(a) a second local oscillator configured to generate a second local oscillator signal; and

(b) a second mixer, responsive to the second local oscillator signal and the frequency-translated channel of interest, that frequency translates the frequency-translated channel of interest to baseband.

75. The apparatus of claim 74 wherein the near-baseband passband is about a channel spacing wide.

76. The apparatus of claim 75 wherein the baseband translator is implemented in the digital domain.

77. The apparatus of claim 76 wherein the baseband translator is further configured to fine-tune the channel of interest by adjustment of the second local oscillator signal.

78. The apparatus of claim 77 wherein the lower edge of the near baseband passband is spaced from DC by at least about the channel spacing.