Read channel apparatus and method for an optical storage system
A read channel apparatus is disclosed for reading data recorded on an optical storage system at a predetermined baud rate. The apparatus asynchronously samples an analog read signal generating from the optical storage system and subtracts an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values. The asynchronous DC-removed sample values are separately interpolated by two interpolators to generate a sequence of synchronous even-time sample values and a sequence of synchronous odd-time sample values respectively. The synchronous even-time and odd-time sample values are separately equalized by two equalizers in accordance with a target spectrum to generate a sequence of even-time equalized sample values and a sequence of odd-time equalized sample values respectively. A DC offset estimator generates the estimated DC offset from the even-time equalized sample values and the odd-time equalized sample values. The interpolators are under the control of a timing recovery controller for synchronizing the even-time and odd-time sample values to the baud rate. In the preferred embodiment, the recorded data are determined from the even-time equalized sample values and the odd-time equalized sample values.
1. A read channel apparatus for reading data recorded on an optical storage system at a predetermined baud rate, comprising:
a sampling device for asynchronously sampling an analog read signal generating from the optical storage system to generate a sequence of asynchronous sample values;
a subtractor for subtracting an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values;
a first interpolator for interpolating the asynchronous DC-removed sample values to generate a sequence of synchronous even-time sample values substantially synchronized to one-half the baud rate;
a second interpolator for interpolating the asynchronous DC-removed sample values to generate a sequence of synchronous odd-time sample values substantially synchronized to one-half the baud rate;
a timing recovery controller, responsive to the even-time sample values and the odd-time sample values, for controlling the first interpolator and the second interpolator respectively in order to synchronize the even-time and odd-time sample values to the baud rate; and
a DC offset estimator for generating the estimated DC offset from the even-time sample values and the odd-time sample values;
wherein the recorded data are determined from the even-time sample values and the odd-time sample values.
2. The read channel apparatus of claim 1 further comprising a sequence detector for detecting the recorded data from the even-time sample values and the odd-time sample values.
3. The read channel apparatus of claim 2 , wherein the sequence detector comprises a Viterbi sequence detector.
4. The read channel apparatus of claim 1 , wherein the sampling device samples the analog read signal at a sampling rate slightly above ½ the baud rate of the data recorded on the optical storage system.
5. The read channel apparatus of claim 4 , wherein the sampling device comprises an analog-to-digital converter.
6. A read channel method for reading data recorded on an optical storage system at a predetermined baud rate, comprising:
asynchronously sampling an analog read signal from the optical storage system to generate a sequence of asynchronous sample values;
subtracting an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values;
separately interpolating the asynchronous DC-removed sample values to respectively generate a sequence of synchronous even-time sample values substantially synchronized to one-half the baud rate and a sequence of synchronous odd-time sample values substantially synchronized to one-half the baud rate;
generating the estimated DC offset from the even-time sample values and the odd-time sample values; and
detecting the recorded data from the even-time sample values and the odd-time sample values.
7. The read channel method of claim 6 , wherein the detecting step performs a run length limitation with Viterbi detection to determine the recorded data from the even-time sample values and the odd-time sample values.
8. The read channel method of claim 6 , wherein the sampling step samples the analog read signal at a sampling rate slightly above ½ the baud rate of the data recorded on the optical storage system.
9. A read channel apparatus for reading data recorded on an optical storage system at a predetermined baud rate, comprising:
a sampling device for asynchronously sampling an analog read signal generating from the optical storage system to generate a sequence of asynchronous sample values;
a subtractor for subtracting an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values;
N interpolators for interpolating the asynchronous DC-removed sample values to generate N sets of synchronous sample values, wherein the N sets of synchronous sample values form a sequence of synchronous sample values substantially synchronized to the baud rate;
a timing recovery controller, responsive to the N sets of synchronous sample values, for controlling the N interpolators respectively in order to synchronize the N sets of synchronous sample values to the baud rate; and
a DC offset estimator for generating the estimated DC offset from the N sets of synchronous sample values;
wherein the recorded data are determined from the N sets of synchronous sample values.
10. The read channel apparatus of claim 9 , further comprising a sequence detector for detecting the recorded data from the N sets of synchronous sample values.
11. The read channel apparatus of claim 9 , further comprising an equalizer equalizing the N sets of synchronous sample values in accordance with a target spectrum to generate N sets of equalized sample values.
12. The read channel apparatus of claim 11 , further comprising a sequence detector for detecting the recorded data from the N sets of equalized sample values.
13. The read channel apparatus of claim 12 , wherein the sequence detector comprises a Viterbi sequence detector.
14. The read channel apparatus of claim 9 , wherein the sampling device samples the analog read signal at a sampling rate slightly above ½ the baud rate of the data recorded on the optical storage system.
15. The read channel apparatus of claim 14 , wherein the sampling device comprises an analog-to-digital converter.
16. A read channel method for reading data recorded on an optical storage system at a predetermined baud rate, comprising:
asynchronously sampling an analog read signal from the optical storage system to generate a sequence of asynchronous sample values;
subtracting an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values;
separately interpolating the asynchronous DC-removed sample values to respectively generate N sets of synchronous sample values, wherein the N sets of synchronous sample values form a sequence of synchronous sample values substantially synchronized to the baud rate;
generating the estimated DC offset from the synchronous sample values; and detecting the recorded data from the synchronous sample values.
17. The read channel method of claim 16 , wherein the detecting step performs a run length limitation with Viterbi detection to determine the recorded data from the synchronous sample values.
18. The read channel method of claim 16 , wherein the sampling step samples the analog read signal at a sampling rate slightly above ½ the baud rate of the data recorded on the optical storage system.
19. The read channel method of claim 16 , further comprising equalizing the N sets of synchronous sample values in accordance with a target spectrum to generate N sets of equalized sample values, and detecting the recorded data from the N sets of equalized sample values.