PRML based magnetic servo position demodulator
View Patent ↗Apparatuses and methods for detecting reference marks on magnetic data storage mediums are described herein. In one variation, the apparatus comprises a magnetic servo position demodulator operable to extract information from the magnetic data storage medium utilizing Partial Response/Maximum Likelihood (PRML) technique. Synchronization marks stored within the PRML channel is then detected utilizing a digital filter. For each of the detected synchronization mark, a further refined position of the synchronization mark can be determined utilizing a mathematical prediction model.
1. A magnetic servo position demodulator comprising:
a transducer operable to detect first and second reference marks on a magnetic medium;
a PRML detector connected to the transducer; and
a first digital filter and a second digital filter coupled to the PRML detector, the first and second digital filters operable to provide information regarding a position of the first reference mark and a position of the second reference mark, respectively, on the magnetic medium, wherein the first reference mark comprises a first synchronization mark and the second reference mark comprises a second synchronization mark, the second digital filter further adapted to modify a position of the second synchronization mark as determined by the PRML detector.
2. The magnetic servo position demodulator according to claim 1 , wherein the second digital filter comprises a mathematical model operable to generate information for determining the position of the second reference mark.
3. The magnetic servo position demodulator according to claim 2 , wherein the mathematical model is derived from an interpolation equation.
4. The magnetic servo position demodulator according to claim 2 , wherein the second digital filter further comprises an error filter.
5. The magnetic servo position demodulator according to claim 4 , wherein the error filter comprises a square absolute error metric.
6. The magnetic servo position demodulator according to claim 4 , wherein the mathematical model is derived from a Lagrange interpolation equation.
7. The magnetic servo position demodulator according to claim 2 , wherein the second digital filter further comprises a peak detector.
8. The magnetic servo position demodulator according to claim 1 , wherein the PRML detector comprises an analog to digital converter and a state machine.
9. The magnetic servo position demodulator according to claim 8 , wherein the PRML detector is configured to detect partial response targets.
10. The magnetic servo position demodulator according to claim 9 , wherein the partial response targets comprise PR4 targets.
11. The magnetic servo position demodulator according to claim 9 , wherein the state machine operates by locating the most probable path through a state space formed by the partial response targets.
12. The magnetic servo position demodulator according to claim 1 , further comprising:
a circuit operable to calculate a position of the transducer relative to the magnetic medium based on the first and the second synchronization marks.
13. The magnetic servo position demodulator according to claim 12 , further comprising:
an actuator operable to displace the transducer based on the calculated position of the transducer.
14. The magnetic servo position demodulator according to claim 1 , wherein the second digital filter calculates an estimated error of the position of the second synchronization mark as determined by the PRML detector, the estimated error being utilized to modify the position of the second synchronization mark as determined by the PRML detector to a new position closer to an actual position of the second synchronization mark.
15. The magnetic servo position demodulator according to claim 14 , wherein the transducer is adapted to read a plurality of channels on the magnetic medium.
16. The magnetic servo position demodulator according to claim 15 , wherein the magnetic medium comprises a magnetic data storage tape.
17. The magnetic servo position demodulator according to claim 1 , wherein the first synchronization mark is contained in a base tone on the magnetic medium, and the second synchronization mark is out of phase with the base tone.
18. The magnetic servo position demodulator according to claim 17 , wherein the second synchronization mark is constructed on the magnetic medium using patterns that are even sub-harmonics of the base tone.
19. A method of determining reference marks on a magnetic medium comprising:
detecting a first synchronization mark on the magnetic medium in a synchronous fashion; and
detecting a second synchronization mark on the magnetic medium in an asynchronous fashion, wherein the detecting the first synchronization mark comprises PRML detection and the detecting the second synchronization mark comprises PRML detection in combination with an error adjustment.
20. The method according to claim 19 , further comprising:
utilizing the first and the second synchronization marks to determine a position of a magneto-resistive head relative to the magnetic medium, wherein the magneto-resistive head is operable to read data stored on the magnetic medium.
21. The method according to claim 20 , wherein the magnetic medium comprises a magnetic tape.
22. The method according to claim 19 , further comprising:
measuring a magnetic flux on the magnetic medium with a transducer.
23. A method of determining reference marks on a magnetic medium comprising:
detecting a first synchronization mark on the magnetic medium in a synchronous fashion; and
detecting a second synchronization mark on the magnetic medium in an asynchronous fashion, wherein the detecting the second synchronization mark comprises calculating an approximate position of the second synchronization mark and utilizing an interpolation to determine a final position of the second synchronization mark.
24. The method according to claim 23 wherein the interpolation comprises Lagrange interpolation.
25. The method according to claim 23 wherein the calculating the approximate position of the second synchronization mark comprises utilizing a square absolute error calculation.
26. A method of determining reference marks on a magnetic medium comprising:
detecting a first synchronization mark on the magnetic medium in a synchronous fashion; and
detecting a second synchronization mark on the magnetic medium in an asynchronous fashion, wherein the first synchronization mark is detected in a base tone on the magnetic medium.
27. The method according to claim 26 wherein a phase position of the second synchronization mark relative to a phase position of the base tone is unknown.
28. The method according to claim 27 wherein the detecting the second synchronization mark comprises calculating a variability of a position of the second synchronization mark relative to the base tone.
29. The method according to claim 28 wherein the detecting the second synchronization mark comprises interpolating a plurality of data sample points which are phase locked with the base tone, and calculating an offset of the position of the second synchronization mark relative to the base tone.
30. An apparatus for detecting a reference mark comprising:
a transducer operable to read information recorded on a data storage medium;
an analog to digital converter operable to covert an analog signal from the transducer into a digital data stream;
a first digital filter operable to detect the reference mark in the digital data stream; and
a second digital filter operable to refine a detected position of the reference mark, wherein the first digital filter comprises a state machine.
31. The apparatus according to claim 30 , wherein the analog to digital converter and the first digital filter are configured as part of a PRML detector.
32. The apparatus according to claim 31 , wherein the PRML detector is configured to detect PR4 targets.
33. The apparatus according to claim 30 , wherein the second digital filter comprises a peak detector.
34. The apparatus according to claim 33 , wherein the second digital filter further comprises a mathematical prediction model.
35. The apparatus according to claim 34 , wherein the mathematical prediction model comprises an interpolation equation.
36. The apparatus according to claim 35 , wherein the data storage medium comprises a magnetic medium.
37. The apparatus according to claim 36 wherein the analog to digital converter and the first digital filter are configured as part of a PRML detector.
38. The apparatus according to claim 30 , wherein the transducer is operable to read a plurality of channels on the data storage medium.
39. The apparatus according to claim 38 , wherein the transducer comprises a magneto-resistive sensor.
40. The apparatus according to claim 30 wherein the second digital filter comprises a detector for determining an approximate position of a peak, which represents the position of the reference mark, within an analog signal generated by the transducer.
41. The apparatus according to claim 40 wherein the second digital filter further comprises a mathematical prediction model configured to determine a more precise position of the reference mark relative to the approximate position of the peak.