Systems and methods for media defect detection
View Patent ↗Various embodiments of the present invention provide systems and methods for media defect detection. For example, a data transfer system is disclosed that includes a data detector, a defect detector and a gating circuit. The data detector provides a soft output, and the defect detector is operable to receive the soft output and the data signal, and to assert a defect indication based at least in part on the soft output and the data signal. The gating circuit is operable to modify the soft output of the detector whenever the defect indication is asserted.
1. A data transfer system, wherein the decoding system comprises:
a data detector, wherein the data detector provides a soft output based on a data signal;
a defect detector, wherein the defect detector includes a soft analysis circuit and a counter circuit, wherein the soft analysis circuit includes a comparator operable to compare the soft output against a soft threshold value, and wherein the counter circuit is operable to determine a number of periods that the soft output is below the soft threshold; and
wherein the defect detector includes:
a data analysis circuit, wherein the data analysis circuit includes a first comparator operable to compare an absolute value of the data signal against a data threshold value; and
a first counter circuit, wherein the first counter circuit is operable to determine a number of periods that the absolute value of the data signal is below the data threshold value.
2. The system of claim 1 , wherein the data detector is selected from a group consisting of: a Viterbi detector and a maximum a posteriori probability detector.
3. The system of claim 1 , wherein the system is a hard disk drive, wherein the hard disk drive includes a storage medium, wherein the data signal is derived from the storage medium, wherein the data detector receives the data signal derived from the storage medium and provides the soft output based at least in part on the data signal, and wherein the defect detector is operable to detect defective regions on the storage medium.
4. The system of claim 1 , wherein the data signal is filtered using a high pass filter prior to comparison against the data threshold value.
5. The system of claim 1 , wherein the data threshold value is programmable.
6. The system of claim 1 , wherein the soft threshold value is programmable.
7. The system of claim 1 , wherein the defect indication is asserted whenever at least one of the first counter and the second counter exceeds a count threshold.
8. The system of claim 7 , wherein the first counter is reset whenever the absolute value of the data signal exceeds the data signal threshold, and wherein the second counter is reset whenever the soft output exceeds the soft threshold.
9. The system of claim 1 , wherein the system is implemented as part of a storage device, and wherein the system further comprises:
a storage medium;
a read/write circuit, wherein at least a portion of the read/write circuit is disposed in relation to the storage medium, and wherein the read/write circuit includes:
the data detector;
the defect detector; and
a positioning controller, wherein the positioning controller is operable to position at least a portion of the read/write circuit in relation to the storage medium.
10. The system of claim 9 , wherein the storage device is incorporated in an electronic system, and wherein the electronic system is selected from a group consisting of: a computer, an audio player, a video player, a stand alone storage system, and a cellular telephone.
11. The system of claim 1 , wherein the defect detector is operable to assert a defect indication based at least in part on the soft output and the data signal; and wherein the system further comprise a gating circuit operable to modify the soft output of the data detector whenever the defect indication is asserted.
12. The system of claim 8 , wherein once the defect indication is asserted, it is maintained asserted for at least a minimum period.
13. The system of claim 12 , wherein the minimum period is programmable.
14. The system of claim 1 , wherein the system is a communication device, wherein the communication device receives information via a communication channel, wherein the data signal is derived from the communication channel, wherein the data detector receives the data signal derived from the communication channel and provides the soft output based at least in part on the data signal, and wherein the defect detector is operable to detect defective periods of the communication channel.
15. A method for defect detection, the method comprising:
receiving a data signal;
performing a detection process on the data signal using a data detector circuit, wherein the data detection process provides a soft output;
comparing the data signal to a data threshold, wherein a data comparison result is asserted whenever the data signal is less than the data threshold for a first determined period;
comparing the soft output to a soft threshold, wherein a soft comparison result is asserted whenever the soft output is less than the soft threshold for a second determined period; and
asserting a defect indicator whenever at least one of the soft comparison result and the data comparison result is asserted.
16. The method of claim 15 , wherein asserting the defect indicator occurs only when both of the soft comparison result and the data comparison result are asserted.
17. The method of claim 15 , wherein the first determined period and the second determined period are the same period, and wherein the same period is programmable.
18. The method of claim 15 , wherein the method further comprises:
determining an absolute value of the data signal, wherein the data signal that is compared with the data threshold is the absolute value of the data signal.
19. The method of claim 15 , wherein the method further comprises:
determining an absolute value of the soft output, wherein the soft output that is compared with the soft threshold is the absolute value of the soft output.
20. The method of claim 15 , wherein the method further comprises:
filtering the data signal, wherein the data signal that is compared with the data threshold is the filtered data signal.
21. A media defect detector system, the system comprising:
a data detector circuit operable to apply a data detection algorithm to a data signal to yield a soft output;
a first comparator circuit operable to compare the data signal to a data threshold to yield a data comparison result indicating when the data signal is less than the data threshold for a first determined period;
a second comparator circuit operable to compare the soft output to a soft threshold to yield a in a soft comparison result indicating when the soft output is less than the soft threshold for a second determined period; and
a defect assertion circuit operable to indicate a defect whenever at least one of the data comparison result indicates the data signal is less than the data threshold for the first determined period and the soft comparison result indicates the soft output is less than the soft threshold for the second determined period.
22. The system of claim 21 , wherein the data signal is filtered using a high pass filter prior to comparison against the data threshold.
23. The system of claim 21 , wherein the data threshold is programmable.
24. The system of claim 21 , wherein the soft threshold is programmable.