Adaptive equalization in a sub-sampled read channel for a disk storage system
First Claim
1. A sampled amplitude read channel for reading data recorded on a disk storage medium at a predetermine baud rate by detecting the recorded data from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, comprising:
- (a) an analog filter for substantially bandlimiting a signal spectrum of the analog read signal to less than 90% of a bandwidth of a target partial response;
(b) a sampling device for asynchronously sampling the analog read signal at less than 90% of the baud rate to generate the discrete-time sample values;
(c) an adaptive equalizer, responsive to the discrete-time sample values, for generating equalized sample values according to the target partial response; and
(d) a discrete-time sequence detector for detecting the recorded data from the equalized sample values.
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Accused Products
Abstract
A sampled amplitude read channel for disk storage systems is disclosed which asynchronously sub-samples an analog read signal significantly below the Nyquist rate (the baud rate) in order to increase the effective data rate without increasing the frequency of the sampling device. Interpolated timing recovery up-samples the asynchronous samples to generate sample values synchronized to the baud rate, and a Viterbi sequence detector detects the recorded digital data from the synchronous sample values. To compensate for the time-varying characteristics of the recording device, a discrete-time equalizer adaptively equalizes the asynchronous sample values using a least mean square (LMS) adaptive algorithm,
W.sub.k+1 =W.sub.k -μ·e.sub.k ·X.sub.k,
where Wk is a vector of FIR filter coefficients, μ is a programmable gain, ek is a sample error between the FIR filter'"'"'s actual output and a desired output, and Xk is a vector of samples values from the FIR filter input.
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Citations
20 Claims
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1. A sampled amplitude read channel for reading data recorded on a disk storage medium at a predetermine baud rate by detecting the recorded data from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, comprising:
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(a) an analog filter for substantially bandlimiting a signal spectrum of the analog read signal to less than 90% of a bandwidth of a target partial response; (b) a sampling device for asynchronously sampling the analog read signal at less than 90% of the baud rate to generate the discrete-time sample values; (c) an adaptive equalizer, responsive to the discrete-time sample values, for generating equalized sample values according to the target partial response; and (d) a discrete-time sequence detector for detecting the recorded data from the equalized sample values. - View Dependent Claims (2, 3, 4, 5)
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6. A method for reading data recorded on a disk storage medium at a predetermined baud rate by detecting the recorded data from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, comprising the steps of:
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(a) substantially bandlimiting a signal spectrum of the analog read signal to less than 90% of a bandwidth of a target partial response; (b) asynchronously sampling the analog read signal at less than 90% of the baud rate to generate the discrete-time sample values; (c) adaptively equalizing the asynchronous sample values according to the target partial response to generate equalized sample values; and (d) detecting the recorded data from the equalized sample values. - View Dependent Claims (7, 8, 9, 10)
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11. A sampled amplitude read channel for reading data recorded on a disk storage medium at a predetermined baud rate by detecting the recorded data from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, comprising:
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(a) a sampling device for asynchronously sampling the analog read signal at less than 90% of the baud rate to generate the discrete-time sample values; (b) an adaptive equalizer, responsive to the discrete-time sample values, for generating equalized sample values according to a target partial response; (c) interpolated timing recovery for up-sampling the equalized sample values to generate synchronous sample values substantially synchronized to the baud rate; and (d) a discrete-time sequence detector for detecting the recorded data from the synchronous sample values. - View Dependent Claims (12, 13, 14, 15)
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16. A sampled amplitude read channel for reading data recorded on a disk storage medium at a predetermine baud rate by detecting the recorded data from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, comprising:
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(a) a sampling device for sampling the analog read signal to generate the discrete-time sample values; (b) a timing recovery circuit for extracting timing information from the discrete-time sample values; (c) an adaptive equalizer, responsive to the discrete-time sample values, for generating equalized sample values according to a target partial response; (d) a sample value estimator, responsive to the equalized sample values, for generating estimated ideal sample values corresponding to the target partial response; (e) a sample error generator, responsive to the discrete-time sample values and the estimated ideal sample values, for generating a sample error value; (f) a sample error adjuster for adjusting the sample error value according to a predetermined criteria to thereby generate an adjusted error value; (g) a coefficient updating circuit for updating coefficients of the adaptive equalizer in response to the adjusted error value; and (h) a discrete-time sequence detector for detecting the recorded data from the equalized sample values. - View Dependent Claims (17, 18, 19, 20)
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Specification