Claims
- 1. A method for downconverting a received signal, the method comprising:
generating an analog carrier signal having a first frequency from a first generation source having a first frequency range and a first frequency resolution; generating a digital carrier signal having a second frequency from a second generation source having a second frequency range and a second frequency resolution, wherein said first frequency range is greater than said second frequency range, and said first frequency resolution is less than said second frequency resolution; and multiplying the received signal by the analog carrier signal and the digital carrier signal to generate a downconverted signal.
- 2. The method of claim 1 further comprising:
measuring a residual frequency error in the downconverted signal; and adjusting the second frequency based on said measuring.
- 3. The method of claim 1 further comprising:
increasing the first frequency by a coarse frequency step size; and decreasing the second frequency by the coarse frequency step size.
- 4. The method of claim 1 further comprising:
decreasing the first frequency by a coarse frequency step size; and increasing the second frequency by the coarse frequency step size.
- 5. A method for downconverting a received signal, the method comprising:
generating an analog carrier signal having a first frequency from a first generation source having a first frequency range and a first frequency resolution; multiplying the received signal by the analog carrier signal to produce an adjusted analog signal; sampling said adjusted analog signal to produce a digital sample stream; generating a digital carrier signal having a second frequency from a second generation source having a second frequency range and a second frequency resolution, wherein said first frequency range is greater than said second frequency range, and said first frequency resolution is less than said second frequency resolution; and multiplying the adjusted analog signal by the digital carrier signal to generate a downconverted signal.
- 6. The method of claim 5 further comprising:
measuring a residual frequency error in the downconverted signal; and adjusting the second frequency based on said measuring.
- 7. The method of claim 5 further comprising:
increasing the first frequency by a coarse frequency step size; and decreasing the second frequency by the coarse frequency step size.
- 8. The method of claim 5 further comprising:
decreasing the first frequency by a coarse frequency step size; and increasing the second frequency by the coarse frequency step size.
- 9. An apparatus for downconverting a received signal, the apparatus comprising:
means for generating an analog carrier signal having a first frequency from a first generation source having a first frequency range and a first frequency resolution; means for generating a digital carrier signal having a second frequency from a second generation source having a second frequency range and a second frequency resolution, wherein said first frequency range is greater than said second frequency range, and said first frequency resolution is less than said second frequency resolution; and means for multiplying the received signal by the analog carrier signal and the digital carrier signal to generate a downconverted signal.
- 10. The method of claim 9 further comprising:
means for measuring a residual frequency error in the downconverted signal; and means for adjusting the second frequency based on said measuring.
- 11. The method of claim 9 further comprising:
means for increasing the first frequency by a coarse frequency step size; and means for decreasing the second frequency by the coarse frequency step size.
- 12. The method of claim 9 further comprising:
means for decreasing the first frequency by a coarse frequency step size; and means for increasing the second frequency by the coarse frequency step size.
- 13. An apparatus for downconverting a received signal, the apparatus comprising:
means for generating an analog carrier signal having a first frequency from a first generation source having a first frequency range and a first frequency resolution; means for multiplying the received signal by the analog carrier signal to produce an adjusted analog signal; sampler for sampling said adjusted analog signal to produce a digital sample stream; means for generating a digital carrier signal having a second frequency from a second generation source having a second frequency range and a second frequency resolution, wherein said first frequency range is greater than said second frequency range, and said first frequency resolution is less than said second frequency resolution; and means for multiplying the adjusted analog signal by the digital carrier signal to generate a downconverted signal.
- 14. The method of claim 13 further comprising:
means for measuring a residual frequency error in the downconverted signal; and means for adjusting the second frequency based on said measuring.
- 15. The method of claim 13 further comprising:
means for increasing the first frequency by a coarse frequency step size; and means for decreasing the second frequency by the coarse frequency step size.
- 16. The method of claim 13 further comprising:
means for decreasing the first frequency by a coarse frequency step size; and means for increasing the second frequency by the coarse frequency step size.
- 17. A receiver apparatus comprising:
analog oscillator having a first frequency range and a first frequency resolution for producing an analog carrier signal having a first frequency; analog mixer for multiplying a received signal by the analog carrier signal to produce a first downconverted signal; digital oscillator having a second frequency range and a second frequency resolution for producing a digital carrier signal having a second frequency, wherein said first frequency range is greater than said second frequency range, and said first frequency resolution is less than said second frequency resolution; and digital mixer for multiplying the first downconverted signal by the digital carrier signal to generate a second downconverted signal.
- 18. The apparatus of claim 17 further comprising:
frequency tracking module for measuring a residual frequency error in the second downconverted signal; and control processor for adjusting a first frequency of the first carrier signal and a second frequency of the second carrier signal based on said measuring.
- 19. The apparatus of claim 18 wherein said frequency tracking module is a frequency tracking loop.
- 20. The apparatus of claim 18 wherein said frequency tracking module is a first-order frequency tracking loop.
- 21. The apparatus of claim 18 wherein said frequency tracking module is a second-order frequency tracking loop.
- 22. The apparatus of claim 17 wherein said digital oscillator is a digital rotator.
- 23. The apparatus of claim 17 wherein said digital oscillator is a direct digital synthesizer.
- 24. The apparatus of claim 17 wherein said analog oscillator is a voltage-controlled oscillator.
- 25. The apparatus of claim 17 wherein said analog oscillator is a temperature-controlled crystal oscillator.
- 26. The apparatus of claim 17 further comprising:
pulse density modulator (PDM) for providing a train of pulses having a duty-cycle that varies in accordance with a digital input signal; and low-pass filter (LPF) for converting the train of pulses into an approximately time-invariant voltage, wherein the magnitude of the time-invariant voltage varies in accordance with the duty-cycle of the train of pulses, and wherein the first frequency varies in accordance with the approximately time-invariant voltage.
- 27. The apparatus of claim 17 further comprising a control processor for adjusting the first frequency and the second frequency.
- 28. The apparatus of claim 27 further comprising a computer-readable media embodying a method for downconverting a received signal, the method comprising:
measuring a residual frequency error in the downconverted signal; and adjusting the second frequency based on said measuring.
- 29. The apparatus of claim 27 further comprising a computer-readable media embodying a method for downconverting a received signal, the method comprising:
increasing the first frequency by a coarse frequency step size; and decreasing the second frequency by the coarse frequency step size.
- 30. The apparatus of claim 27 further comprising a computer-readable media embodying a method for downconverting a received signal, the method comprising:
decreasing the first frequency by a coarse frequency step size; and increasing the second frequency by the coarse frequency step size.
- 31. A computer-readable media embodying a method for downconverting a received signal, the method comprising:
generating a first frequency control signal for controlling a first frequency of an analog carrier signal output by an analog oscillator having a first frequency range and a first frequency resolution; generating a second frequency control signal for controlling a second frequency of a digital carrier signal output by a digital oscillator having a second frequency range and a second frequency resolution, wherein the first frequency range is greater than the second frequency range, and the first frequency resolution is less than said second frequency resolution; measuring a residual frequency error in a downconverted signal; and adjusting the second frequency based on said measuring.
- 32. The computer-readable media of claim 31, wherein the method further comprises:
adjusting the first frequency control signal to increase the first frequency by a coarse frequency step size; and adjusting the second frequency control signal to decrease the second frequency by the coarse frequency step size.
- 33. The computer-readable media of claim 31, wherein the method further comprises:
adjusting the first frequency control signal to decrease the first frequency by a coarse frequency step size; and adjusting the second frequency control signal to increase the second frequency by the coarse frequency step size.
- 34. The computer-readable media of claim 31, wherein the first frequency control signal is a digital signal provided to a pulse density modulator.
- 35. The computer-readable media of claim 31, wherein the second frequency control signal is a digital signal provided to a digital rotator.
- 36. The computer-readable media of claim 31, wherein the second frequency control signal is a digital signal provided to a direct digital synthesizer.
CROSS REFERENCE
[0001] This application claims priority from U.S. Provisional Application No. 60/337,469, filed Nov. 9, 2001, entitled “Method and Apparatus for Matching Receiver Carrier Frequency.”
Provisional Applications (1)
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Number |
Date |
Country |
|
60337469 |
Nov 2001 |
US |