Position error signal burst demodulation

• US 9,979,573 B1
• Filed: 12/23/2016
• Issued: 05/22/2018
• Est. Priority Date: 12/23/2016
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Marrow, Marcus, Bellorado, Jason Vincent, Nguyen, Trung Thuc
• Primary Examiner(s): Ha, Dac
• Application Number:
  US15/390,447
• Time in Patent Office: 515 Days
• CPC Class Codes: G06F 7/4818 using coordinate rotation digital computer [CORDIC]
• CPC Class Codes: G06F 7/5446 using crossaddition algorithms, e.g. CORDIC
• CPC Class Codes: G11B 5/59688 Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits

Abstract

A method may generate a demodulated sine component for a sequence of samples of a servo burst window of a position error signal using a sine weight look up table and generate a demodulated cosine component for the sequence of samples of the servo burst window of the position error signal using a cosine weight look up table. The sine weight and the cosine weight look up tables may have indexes representing a phase range. The method may generate a demodulated phase component signal and a demodulated amplitude component signal for the sequence of samples of the servo burst window of the position error signal based on the demodulated sine component and the demodulated cosine component using a Coordinate Rotation Digital Computer at least in part by iteratively rotating a vector based on the demodulated sine component and the demodulated cosine component and summing angular changes in the vector.

Claims

1. An apparatus comprising:

a circuit configured to;

generate a demodulated phase component signal and a demodulated amplitude component signal based on a servo burst window of a position error signal using a CORDIC (COordinate Rotation DIgital Computer); and

the circuit being configured to perform the generating of the demodulated phase component signal and the demodulated amplitude component signal using the CORDIC at least in part by iteratively rotating a vector and summing angular changes in the vector.

2. The apparatus of claim 1, further comprising:

the vector being based on a demodulated sine component and a demodulated cosine component of the servo burst window of the position error signal.

3. The apparatus of claim 2, further comprising the circuit further configured to:

generate the demodulated sine component using a sine weight look up table; and

generate the demodulated cosine component using a cosine weight look up table.

4. The apparatus of claim 3, further comprising the circuit further configured to:

receive a plurality of samples of a continuous time input signal corresponding to the servo burst window of the position error signal;

generate a sequence of digitized samples of the servo burst window of the position error signal based on the continuous time input signal;

perform the generating of the demodulated sine component and the demodulated cosine component based at least in part on the digitized samples.

5. The apparatus of claim 4 further comprising the circuit further configured to:

perform the generating of the demodulated sine component and the demodulated cosine component based at least in part on a phase offset, a burst frequency, and a burst length.

6. The apparatus of claim 5, further comprising the circuit further configured to:

determine the phase offset based on a timing signal, a step size and a number of solutions.

7. The apparatus of claim 5, further comprising the circuit configured to:

select a sine weight from the sine weight look up table using an index representing phases, the phase offset being used to offset the index value.

8. The apparatus of claim 4, further comprising the circuit configured to:

multiply each sample of the servo burst window with a respective sine weight output from the sine weight look up table to generate a plurality of multiplication results; and

accumulate a sum of the plurality of multiplication results.

9. A position error signal burst demodulation system comprising:

a sine demodulation circuit configured to;

generate a demodulated sine component using a sine weight look up table at least in part by;

multiplying each sample of a sequence of digitized samples of a servo burst window of a position error signal with a respective sine weight output from the sine weight look up table to generate a plurality of multiplication results; and

accumulating a sum of the plurality of multiplication results; and

a cosine demodulation circuit configured to;

generate a demodulated cosine component using a cosine weight look up table.

10. The system of claim 9, further comprising:

an analog to digital converter configured to;

receive a plurality of samples of a continuous time input signal corresponding to the servo burst window of the position error signal;

generate the samples of the sequence of digitized samples of the servo burst window of the position error signal based on the continuous time input signal.

11. The system of claim 10 further comprising the sine demodulation circuit configured to:

determine the demodulated sine component based at least in part on a phase offset, a burst frequency, and a burst length.

12. The system of claim 11 further comprising the sine demodulation circuit configured to:

select a sine weight from the sine weight look up table using an index representing phases, the phase offset being used to offset the index value.

13. The system of claim 9 further comprising:

a phase and amplitude demodulator configured to;

generate a demodulated phase component signal and a demodulated amplitude component signal based on the demodulated sine component and the demodulated cosine component of the servo burst window of the position error signal using a CORDIC (COordinate Rotation DIgital Computer).

14. The system of claim 13 further comprising the phase and amplitude demodulator configured to:

perform the generating of the demodulated phase component signal using the CORDIC at least in part by;

iteratively rotating a vector based on the demodulated sine component and the demodulated cosine component; and

summing angular changes in the vector.

15. A method comprising:

generating a demodulated sine component for a sequence of samples of a servo burst window of a position error signal using a sine weight look up table;

generating a demodulated cosine component for the sequence of samples of the servo burst window of the position error signal using a cosine weight look up table, the sine weight look up table and the cosine weight look up table having indexes representing a phase range;

generating a demodulated phase component signal and a demodulated amplitude component signal for the sequence of samples of the servo burst window of the position error signal based on the demodulated sine component and the demodulated cosine component using a CORDIC (COordinate Rotation DIgital Computer) at least in part by;

iteratively rotating a vector based on the demodulated sine component and the demodulated cosine component; and

summing angular changes in the vector.

16. The method of claim 15, the generating the demodulated sine component comprising:

multiplying each sample of the sequence of samples of the servo burst window of the position error signal with a respective sine weight output from the sine weight look up table to generate a plurality of multiplication results; and

accumulating a sum of the plurality of multiplication results.

17. The method of claim 16 further comprising:

receiving a plurality of samples of a continuous time input signal corresponding to the servo burst window of the position error signal;

generating the samples of the sequence of samples of the servo burst window of the position error signal based on the continuous time input signal.

18. The method of claim 15 further comprising:

determining the demodulated sine component based at least in part on a phase offset at least in part by selecting a sine weight for each sample of the sequence of the samples of the servo burst window from the sine weight look up table using the phase offset to offset the index value.