Claims
- 1. A system for reading information stored on a magnetic medium by generating data symbols from a signal encoded at a baud rate with data including an acquisition preamble defining an acquisition frequency and an acquisition phase, comprising:
a frequency synchronization loop configured to generate a sampling clock synchronized approximately to the acquisition frequency and the acquisition phase of the encoded data signal; a signal sampler coupled to the frequency synchronization loop and configured to sample the encoded data signal in response to the sampling clock to produce a plurality of data samples; an interpolator coupled to the frequency synchronization loop and configured to produce in response to the sampling clock interpolated samples from the data samples; and a phase synchronization loop coupled to the interpolator and configured to synchronize the interpolator to the baud rate of the encoded data signal.
- 2. The system of claim 1, wherein the frequency synchronization loop comprises a delay-locked loop configured to synthesize the sampling clock.
- 3. The system of claim 2, wherein the delay-locked loop comprises a phase detector and a filter coupled in series and configured to control signal propagation delay through the delay-locked loop.
- 4. The system of claim 3, further comprising a fixed frequency signal generator coupled to the delay-locked loop.
- 5. The system of claim 2, further comprising a feedback loop coupled between an output of the signal sampler and an input of the frequency synchronization loop.
- 6. The system of claim 5, wherein the feedback loop comprises a phase detector configured to generate a phase error signal based upon the difference between estimated samples and the data samples.
- 7. The system of claim 6, wherein the feedback loop comprises a loop filter configured to filter the phase error signal to produce a filtered phase error signal operable to synchronize the synthesized sampling clock approximately to the acquisition frequency of the encoded data signal.
- 8. The system of claim 1, wherein the phase synchronization loop comprises a phase detector configured to generate a phase error signal based upon the difference between estimated samples and the data samples.
- 9. The system of claim 8, wherein the phase synchronization loop is configured to time-shift the response of the interpolator.
- 10. The system of claim 9, wherein the phase synchronization loop comprises a memory storing a plurality of sets of coefficients, wherein each coefficient set defines an interpolator response shifted in time relative to the other coefficient sets.
- 11. The system of claim 9, wherein the phase synchronization loop is configured to time-shift the interpolator response by only a fraction of a sampling clock period.
- 12. The system of claim 8, further comprising a phase calibrator coupled between the frequency synchronization loop and the phase synchronization loop and configured to calibrate the frequency synchronization loop after an accumulation of phase errors generated by the phase detector of the phase synchronization loop exceeds a threshold value.
- 13. The system of claim 12, wherein the phase calibrator is configured to calibrate the frequency synchronization loop by adjusting the phase of the sampling clock.
- 14. The system of claim 12, wherein the phase calibrator comprises a feedback isolator for approximately canceling a phase transient generated at the phase synchronization loop as a result of a frequency synchronization loop calibration.
- 15. The system of claim 1, wherein the frequency synchronization loop is configured to fix the sampling clock frequency before the signal sampler has sampled the entire acquisition preamble of the encoded data signal.
- 16. The system of claim 1, wherein the phase synchronization loop is configured to synchronize the interpolator during and after the signal sampler has sampled the entire acquisition preamble of the encoded data signal.
- 17. A system for reading information stored on a magnetic medium by generating data symbols from a signal encoded with data including an acquisition preamble defining an acquisition frequency and an acquisition phase, comprising:
a signal sampler configured to sample the encoded data signal in response to a sampling clock to produce a plurality of data samples; a frequency synchronization loop coupled to the signal sampler and configured to generate the sampling clock synchronized approximately to the acquisition frequency and the acquisition phase of the encoded data signal, wherein the frequency synchronization loop comprises a delay-locked loop configured to synthesize the sampling clock.
- 18. The system of claim 17, further comprising a phase calibrator coupled to the frequency synchronization loop and configured to calibrate the frequency synchronization loop after an accumulation of phase errors exceeds a threshold value.
- 19. The system of claim 18, wherein the phase calibrator is configured to calibrate the frequency synchronization loop by adjusting the phase of the sampling clock.
- 20. A method of reading information stored on a magnetic medium by generating data symbols from a signal encoded at a baud rate with data including an acquisition preamble defining an acquisition frequency and an acquisition phase, comprising:
sampling the encoded data signal in response to a sampling clock to produce a plurality of data samples; generating the sampling clock synchronized approximately to the acquisition frequency and the acquisition phase of the encoded data signal; in response to the sampling clock, interpolating the data samples to produce interpolated samples; and synchronizing the interpolation of the data samples to the baud rate of the encoded data signal.
- 21. The method of claim 20, wherein synchronizing the interpolation of data samples comprises generating a phase error signal based upon the difference between estimated samples and the data samples.
- 22. The method of claim 21, wherein synchronizing the interpolation of data samples comprises time-shifting the data samples.
- 23. The method of claim 22, wherein time-shifting the data samples comprises loading into an interpolator one of a plurality of sets of coefficients, wherein each coefficient set defines an interpolator response shifted in time relative to the other coefficient sets.
- 24. The method of claim 22, wherein the data samples are time-shifted by only a fraction of a sampling clock period.
- 25. The method of claim 21, further comprising calibrating a frequency synchronization loop after an accumulation of phase errors exceeds a threshold value.
- 26. The method of claim 25, wherein the frequency synchronization loop is calibrated by adjusting the phase of the sampling clock.
- 27. The method of claim 25, further comprising approximately canceling a phase transient generated as a result of calibrating the frequency synchronization loop.
- 28. The method of claim 20, wherein the sampling clock frequency is fixed before the entire acquisition preamble of the encoded data signal has been sampled.
- 29. The method of claim 20, wherein the interpolation of data samples is synchronized during and after the entire acquisition preamble of the encoded data signal has been sampled.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Provisional U.S. Application Serial No. 60/212,903, filed Jun. 20, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
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60212903 |
Jun 2000 |
US |