Position error signal burst demodulation

1. An apparatus comprising:

a circuit having a CORDIC (Coordinate Rotation Digital Computer), the circuit configured to:

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

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

determine demodulated sine and cosine values using cosine and sine weight LUTs based on the digitized samples, the phase offset, a burst frequency, and a burst length component based at least in part on the digitized samples;

generate a demodulated phase component signal and a demodulated amplitude component signal based on a based on a phase direction value, a number of iterations value, the demodulated cosine value and the demodulated sine value using the CORDIC; and

the circuit having one or more outputs to provide the demodulated phase component signal and the demodulated amplitude component signal to a servo control system.

2. The apparatus of claim 1 , further comprising the circuit further 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 determining an angular change in the rotated vector.

3. The apparatus of claim 2 , 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.

4. The apparatus of claim 3 , 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.

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 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.

7. 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.

8. The apparatus of claim 1 further comprising a servo control system coupled to the circuit and configured to control a servo positioning based on the demodulated phase component signal and the demodulated amplitude component signal.

9. A control system comprising:

a sine demodulation circuit configured to:

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

a cosine demodulation circuit configured to:

generate a demodulated cosine component using a cosine weight look up table; and

a phase and amplitude demodulator circuit including a CORDIC (Coordinate Rotation Digital Computer) 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; and

a servo control system configured to control a servo positioning based on the demodulated phase component signal and the demodulated amplitude component signal.

10. The control system of claim 9 further comprising:

the cosine demodulation circuit configured to generate the demodulated cosine component 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 cosine weight output from the cosine weight look up table to generate a plurality of multiplication results; and

accumulating a sum of the plurality of multiplication results.

11. The control system of claim 10 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; and

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.

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

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

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

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

14. The control system of claim 9 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

determining an 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; and

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

determining an angular change in the vector resulting from the iterative rotating of the vector.

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

multiplying each sample of the sequence of samples of the servo burst window of the position error signal with a respective cosine weight output from the cosine 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; and

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