Simplified high frequency tuner and tuning method

• US 7,925,238 B2
• Filed: 07/10/2008
• Issued: 04/12/2011
• 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): Jackson; Blane J
• Application Number:
  US12/170,978
• Publication Number:
  US 20080318538A1
• Time in Patent Office: 1,006 Days
• Field of Search: 455/296, 455/302, 455/304, 455/305, 455/306, 455/307, 455/310, 455/313, 455/323, 455/324, 455/256, 455/257, 455/258
• 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. An apparatus for tuning any channel of interest from a channelized spectrum having a predetermined channel spacing, the apparatus comprising:

(a) a local oscillator configured to generate a local oscillator signal frequency either above or below the frequency of the channel of interest;

(b) a first mixer and a second mixer, each having an input coupled to the local oscillator and a radio frequency antenna configured to receive the channel of interest, the first and the second mixer configured to frequency translate the channel of interest;

(c) a filtering block having two inputs, the inputs being respectively coupled to the first and second mixer outputs and further wherein one of the inputs is in approximate phase quadrature with a second input, the filtering block configured to filter the frequency translated channel of interest; and

,

(d) a selector structured to dynamically select either a frequency translated upper high frequency spectrum of interest or a frequency translated lower high frequency spectrum of interest for demodulation;

(e) wherein the frequency translated channel of interest is within a near-baseband passband spaced from DC by at least about 20 kHz.

2. The apparatus of claim 1 wherein the selected high frequency spectrum of interest is within a near-baseband passband that is spaced from DC by less than the channel spacing but at least by about 20 kHz.

3. The apparatus of claim 1 wherein the selected high frequency spectrum of interest falls within a near-baseband passband that is spaced from DC by at least about the channel spacing.

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

(a) a tunable local oscillator configured to generate a local oscillator signal frequency either above or below the frequency of the channel of interest, and having a tuning step size approximately equal to the channel spacing;

(b) a first and a second mixer respectively coupled to the local oscillator signal and a quadrature local oscillator signal having an approximate 90 degree phase shift relative to the local oscillator, and each mixer further coupled to a radio frequency antenna configured to receive the channel of interest, the first and second mixers configured to selectively frequency translate the channel of interest from either above the local oscillator frequency or below the local oscillator frequency;

(c) a phase shifting element coupled to either the first or the second mixer output and configured to generate a signal that is in phase quadrature with the input signal; and

,

(d) a selector structured to dynamically select either an upper high frequency spectrum of interest or the lower high frequency spectrum of interest from the frequency translated signal;

(e) wherein the selected high or low frequency spectrum of interest falls within a near-baseband passband that is spaced from DC by at least about 20 kHz.

5. The apparatus of claim 4 wherein the selected high frequency spectrum of interest falls within a near-baseband passband that is spaced from DC by at least about the channel spacing.

6. The apparatus of claim 4 wherein the selected high frequency spectrum of interest is within a near-baseband passband that is spaced from DC by less than the channel spacing but at least by about 20 kHz.

7. The apparatus of claim 6 wherein the selector operation includes selecting a local oscillator frequency that is either above or below the frequency of the channel of interest.

8. The apparatus of claim 7 wherein the selector operation further includes operating on the near baseband signal to select either the upper high frequency spectrum of interest or the lower high frequency spectrum of interest.

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

(a) a local oscillator configured to generate a local oscillator signal that is coarse-tunable across the channelized spectrum with a step size that at least an integer multiple of the channel spacing;

(b) a filtering element defining a near-baseband passband spaced from DC by at least about 20;

(c) a first and a second mixer, each coupled to the local oscillator and a radio frequency antenna configured to receive the channelized signal of interest, and the mixers configured to translate 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

(d) a control structure that is configured to dynamically select one of the high frequency spectra of interest.

10. The apparatus of claim 9 wherein the filtering element defines a near-baseband passband spaced from DC by less than the channel spacing but at least by about 20 kHz.

11. The apparatus of claim 9 wherein the filtering element defines a near-baseband passband spaced from DC by at least about the channel spacing.

12. An RF tuner comprising:

(a) analog circuitry including

(i) a local oscillator that provides a first local oscillator signal having a frequency FLO and a second local oscillator signal having the frequency FLO approximately in quadrature to the first local oscillator signal,

(ii) a first mixer operable to mix the first local oscillator signal with an incoming signal to provide a first mixer output comprised of an upper high frequency signal spectrum of interest above FLO and a lower high frequency signal spectrum of interest below FLO wherein both the upper high frequency signal spectrum of interest and the lower high frequency spectrum of interest are frequency-translated to within a near-baseband passband by the mixing with the first local oscillator signal,

(iii) a second mixer operable to mix the second local oscillator signal with the incoming signal to provide a second mixer output comprised of the upper high frequency signal spectrum of interest above FLO and the lower high frequency signal spectrum of interest below FLO, wherein both the upper high frequency signal spectrum of interest and the lower high frequency signal spectrum of interest are frequency-translated to within the near-baseband passband by the mixing with the second local oscillator signal,

(iv) first circuitry configured to at least filter the frequency spectrum output by the first mixer, and

(v) second circuitry configured to at least filter the frequency spectrum output by the second mixer; and

(b) digital circuitry including;

(i) a first analog-to-digital converter that provides a first converter output comprised of the output of the first circuitry configured to at least filter the frequency spectrum converted from analog to digital format, and

(ii) a second analog-to-digital converter that provides a second converter output comprised of the output of the second circuitry configured to at least filter the frequency spectrum converted from analog to digital format; and

(c) wherein the digital circuitry is adapted to combine the first and second converter outputs to provide an image-rejected signal within the near-baseband passband by substantially rejecting the near-baseband image of a dynamically selectable one of the upper high frequency signal spectrum of interest and the lower high frequency signal spectrum of interest.

13. The apparatus of claim 12 wherein the digital circuitry further performs fine tuning of the digitized signals received from the first and second analog to digital converters.

14. The apparatus of claim 12 wherein the digital circuitry controls amplitude correction of the digitized signals received from the first and second analog to digital converters.

15. The apparatus of claim 12 wherein the digital circuitry performs phase correction of the digitized signals received from the first and second analog to digital converters.

16. The apparatus of claim 12 wherein the local oscillator step size is dependent upon the selection of the near-baseband passband width.

17. The apparatus of claim 12 wherein the width of the near-baseband passband is based upon the spectrum channel width.

18. The apparatus of claim 12 wherein the width of the near-baseband passband is based upon the bandwidth of the desired signal to be tuned.

19. The apparatus of claim 12 wherein the passband width of the first and second frequency selective circuitry is adjustable.

20. The apparatus of claim 12 wherein the width of the near-baseband passband includes a frequency adjustment.

21. The apparatus of claim 12 wherein at a first local oscillator frequency, the digital portion is configured to recover the upper high frequency spectrum of interest and at a second local oscillator frequency, the digital portion is configured to recover the lower high frequency signal spectrum of interest.

22. The apparatus of claim 12 wherein the digital portion includes a variable decimating filter.

23. The apparatus of claim 12 wherein the digital portion includes a Hilbert transform.

24. The apparatus of claim 12 wherein the LO step size is configurable to be no less than twice the channel spacing of a channelized spectrum from which tuning is to be performed.

25. The apparatus of claim 12 wherein the digital portion is further configured to translate a selected portion of said near-baseband image-rejected signal to baseband.

26. The apparatus of claim 12 wherein the first and second circuitry comprises filters.