Servo field preamble detector and methods for use therewith

1. A servo field preamble detector for use in a disk drive, the servo field preamble detector comprising:

an upsampling module that generates a plurality of upsampled read samples by upsampling a discrete-time read signal by an upsampling factor;

an interpolation filter module, operably coupled to the upsampling module, that generates a plurality of interpolated read samples from the plurality of up sampled read samples;

a peak detection module, operably coupled to the interpolation filter, that identifies a plurality of peak samples from the plurality of interpolated read samples;

a magnitude estimation module, operably coupled to the peak detection module, that convolves the plurality of peak samples by a sequence of alternating polarities to form a plurality of peak magnitude signals and that generates a magnitude estimation signal based on the sum of n successive peak magnitude signals; and

a comparison module, operably coupled to the magnitude estimation module, that compares the magnitude estimation signal to a magnitude threshold and that generates a servo preamble detection signal when the magnitude estimation signal compares favorably to the magnitude threshold.

2. The servo field preamble detector of claim 1 wherein the interpolation filter module includes an interpolation filter that has an impulse response that is a finite sinc function.

3. The servo field preamble detector of claim 1 wherein the peak detection module identifies one of the plurality of peak samples by comparing the magnitude of successive ones of the plurality of interpolated read samples.

4. The servo field preamble detector of claim 1 wherein the peak detection module identifies one of the plurality of peak samples by calculating a plurality of successive gradients and detecting an inversion in the polarity between two successive gradients of the plurality of successive gradients.

5. The servo field preamble detector of claim 1 wherein the peak detection module identifies one of the plurality of peak samples by identifying one of a plurality of interpolated read samples with the greatest absolute magnitude.

6. The servo field preamble detector of claim 1 wherein n is an integer power of two.

7. A method for use in a disk controller of a disk drive, the method comprising:

generating a plurality of upsampled read samples by upsampling a discrete-time read signal by an upsampling factor;

generating a plurality of interpolated read samples from the plurality of upsampled read samples;

identifying a plurality of peak samples from the plurality of interpolated read samples;

generating a magnitude estimation signal from the plurality of peak samples;

comparing the magnitude estimation signal to a magnitude threshold; and

generating a servo preamble detection signal when the magnitude estimation signal compares favorably to the magnitude threshold.

8. The method of claim 7 wherein the step of generating a plurality of interpolated read samples includes filtering the plurality of upsampled read samples with a filter that has an impulse response that is a finite sinc function.

9. The method of claim 7 wherein the step of identifying a plurality of peak samples includes identifying one of the plurality of peak samples by comparing the magnitude of successive ones of the plurality of interpolated read samples.

10. The method of claim 7 wherein the step of identifying a plurality of peak samples includes identifying one of the plurality of peak samples by calculating a plurality of successive gradients and detecting an inversion in the polarity between two successive gradients of the plurality of successive gradients.

11. The method of claim 7 wherein the step of identifying a plurality of peak samples includes identifying one of the plurality of peak samples by identifying one of a plurality of filtered samples with the greatest absolute magnitude.

12. The method of claim 7 wherein the step of generating a magnitude estimation signal includes multiplying the plurality of peak samples by a sequence of alternating polarities to form a plurality of peak magnitude signals.

13. The method of claim 7 wherein the step of generating a magnitude estimation signal generates the magnitude estimation signal based on the sum of n successive peak magnitude signals.

14. A servo field preamble detector for use in a disk controller of a disk drive, the servo field preamble detector comprising:

a peak detection module that identifies a plurality of peak samples from a plurality of read samples;

a magnitude estimation module, operably coupled to the peak detection module, that generates a magnitude estimation signal from the plurality of peak samples, wherein the magnitude estimation module convolves the plurality of peak samples by a sequence of alternating polarities to form a plurality of peak magnitude signals; and

a comparison module, operably coupled to the magnitude estimation module, that compares the magnitude estimation signal to a magnitude threshold and that generates a servo preamble detection signal when the magnitude estimation signal compares favorably to the magnitude threshold.

15. The servo field preamble detector of claim 14 wherein the interpolation filter module includes an interpolation filter that has an impulse response that is a finite sinc function.

16. The servo field preamble detector of claim 14 wherein the peak detection module identifies one of the plurality of peak samples by comparing the magnitude of successive ones of the plurality of read samples.

17. The servo field preamble detector of claim 14 wherein the peak detection module identifies one of the plurality of peak samples by calculating a plurality of successive gradients and detecting an inversion in the polarity between two successive gradients of the plurality of successive gradients.

18. The servo field preamble detector of claim 14 wherein the peak detection module identifies one of the plurality of peak samples by identifying one of a plurality of read samples with the greatest absolute magnitude.

19. The servo field preamble detector of claim 14 wherein the magnitude estimation module generates the magnitude estimation signal based on the sum of n successive peak magnitude signals.

20. The servo field preamble detector of claim 14 further comprising:

an upsampling module that generates a plurality of upsampled read samples by upsampling a discrete-time read signal by an upsampling factor; and

an interpolation filter module, operably coupled to the upsampling module, that generates the plurality of read samples by filtering the plurality of upsampled read samples.

21. The servo field preamble detector of claim 14 wherein the read samples are generated by oversampling a read signal at a sampling frequency that is a multiple M above a Nyquist sampling rate of the read signal.