Patent ID: 6111710
Filing Date: 2000-08-29
Classification: G11B,H04L

Abstract:
A sampled amplitude read channel for reading data recorded on a disk storage medium at a predetermined baud rate by detecting an estimated data sequence from discrete-time sample values generated by sampling an analog read signal from a read head positioned over the disk storage medium, the recorded data comprising data sectors comprised of an acquisition preamble preceding a user data field, the sampled amplitude read channel comprising:(a) a variable gain amplifier (VGA) for adjusting an amplitude of the analog read signal before sampling;(b) a sampling device for sampling the analog read signal asynchronous to the baud rate of the recorded data to generate asynchronous sample values;(c) an interpolated timing recovery circuit, responsive to the asynchronous sample values, for generating synchronous sample values substantially synchronized to the baud rate of the recorded data;(d) an asynchronous gain control circuit for generating an asynchronous gain error from the asynchronous sample values by computing a discrete-time fourier transform (DTFT) of the asynchronous sample values to estimate a magnitude of the analog read signal at the output of the VGA, the asynchronous gain error for controlling operation of the VGA when the read channel is reading the acquisition preamble in order to synchronize the interpolated timing recovery circuit to the baud rate of the recorded data during a read operation;(e) a synchronous gain control circuit for generating a synchronous gain error from the synchronous sample values, the synchronous gain error for controlling operation of the VGA when the read channel is reading the user data field; and(f) a discrete-time sequence detector for detecting the recorded data from the synchronous sample values.