Zero phase start estimation in readback signals
A data storage system identifies analog-to-digital conversion samples with amplitude below a certain threshold. Remaining samples are grouped according to phase into one or more quadrants. A multi-coordinate with overlapping quadrants is used to further differentiate sample points. The system then computes an average phase for zero phase start estimation.
1. A computer apparatus comprising:
a processor;
memory connected to the processor; and
computer executable program code configured to execute on the processor, wherein the computer executable program code is configured to:
receive a plurality of readback signal samples;
determine a sin term for each readback signal sample;
determine a cos term for each readback signal sample;
organize the readback signal samples according to the corresponding sin terms and cos terms; and
compute an input phase based on the organized readback signal samples.
2. The computer apparatus of claim 1 , wherein organizing the readback signal samples comprises:
defining a first coordinate system, a first axis of the first coordinate system corresponding to sin function and a second axis of the first coordinate system corresponding to a cos function; and
placing each readback signal sample in the first coordinate system.
3. The computer apparatus of claim 2 , wherein the computer executable program code is further configured to:
maintain a region counter corresponding to each of a plurality of regions in the first coordinate system;
increment a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identify when one of the plurality of regions includes a threshold number of readback signal samples.
4. The computer apparatus of claim 2 , wherein organizing the readback signal samples further comprises:
defining a second coordinate system, a first axis of the second coordinate system corresponding to sin function and a second axis of the second coordinate system corresponding to a cos function, the second coordinate system being offset from the first coordinate system by a predetermined angle; and
placing each readback signal sample in the second coordinate system.
5. The computer apparatus of claim 4 , wherein the computer executable program code is further configured to:
maintain a region counter corresponding to each of a plurality of regions in the second coordinate system;
increment a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identify when one of the plurality of regions includes a threshold number of readback signal samples.
6. The computer apparatus of claim 4 , wherein each readback signal sample comprises a 4T signal and each of the first coordinate system and second coordinate system comprises four quadrants.
7. The computer apparatus of claim 1 , wherein the computer executable program code is further configured to:
define an amplitude threshold; and
exclude any readback signal samples that fall below the amplitude threshold from the computation of input phase.
8. A method for estimating a readback signal phase comprising:
receiving a plurality of readback signal samples;
determining a sin term for each readback signal sample;
determining a cos term for each readback signal sample;
organizing the readback signal samples according to the corresponding sin terms and cos terms; and
computing an input phase based on the organized readback signal samples.
9. The method of claim 8 , wherein organizing the readback signal samples comprises:
defining a first coordinate system, a first axis of the first coordinate system corresponding to sin function and a second axis of the first coordinate system corresponding to a cos function; and
placing each readback signal sample in the first coordinate system.
10. The method of claim 9 , further comprising:
maintaining a region counter corresponding to each of a plurality of regions in the first coordinate system;
incrementing a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identifying when one of the plurality of regions includes a threshold number of readback signal samples.
11. The method of claim 9 , wherein organizing the readback signal samples further comprises:
defining a second coordinate system, a first axis of the second coordinate system corresponding to sin function and a second axis of the second coordinate system corresponding to a cos function, the second coordinate system being offset from the first coordinate system by a predetermined angle; and
placing each readback signal sample in the second coordinate system.
12. The method of claim 11 , further comprising:
maintaining a region counter corresponding to each of a plurality of regions in the second coordinate system;
incrementing a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identifying when one of the plurality of regions includes a threshold number of readback signal samples.
13. The method of claim 8 , further comprising:
defining an amplitude threshold; and
excluding any readback signal samples that fall below the amplitude threshold from the computation of input phase.
14. A data storage system comprising:
a processor;
memory connected to the processor;
a data storage element connected to the processor; and
computer executable program code configured to execute on the processor, wherein the computer executable program code is configured to:
receive a plurality of readback signal samples from the data storage element;
determine a sin term for each readback signal sample;
determine a cos term for each readback signal sample;
organize the readback signal samples according to the corresponding sin terms and cos terms; and
compute an input phase based on the organized readback signal samples.
15. The data storage system of claim 14 , wherein organizing the readback signal samples comprises:
defining a first coordinate system, a first axis of the first coordinate system corresponding to sin function and a second axis of the first coordinate system corresponding to a cos function; and
placing each readback signal sample in the first coordinate system.
16. The data storage system of claim 15 , wherein the computer executable program code is further configured to:
maintain a region counter corresponding to each of a plurality of regions in the first coordinate system;
increment a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identify when one of the plurality of regions includes a threshold number of readback signal samples.
17. The data storage system of claim 15 , wherein organizing the readback signal samples further comprises:
defining a second coordinate system, a first axis of the second coordinate system corresponding to sin function and a second axis of the second coordinate system corresponding to a cos function, the second coordinate system being offset from the first coordinate system by a predetermined angle; and
placing each readback signal sample in the second coordinate system.
18. The data storage system of claim 17 , wherein the computer executable program code is further configured to:
maintain a region counter corresponding to each of a plurality of regions in the second coordinate system;
increment a corresponding region counter each time a readback signal sample is organized into the corresponding region; and
identify when one of the plurality of regions includes a threshold number of readback signal samples.
19. The data storage system of claim 17 , wherein each readback signal sample comprises a 4T signal and each of the first coordinate system and second coordinate system comprises four quadrants.
20. The data storage system of claim 14 , wherein the computer executable program code is further configured to:
define an amplitude threshold; and
exclude any readback signal samples that fall below the amplitude threshold from the computation of input phase.