Patent ID: 6369741
Filing Date: 2002-04-09
Classification: G11B

Abstract:
A read channel for a mass storage device having a plurality of information media, the read channel comprising:a read head for reading an information medium and generating a read signal based thereon; a pre-amplification stage for amplifying the read signal generated by the read head; a variable gain amplifier stage receiving the read signal from the pre-amplification stage; a first digital/analog converter for controlling the variable gain amplifier; an attenuating circuit for attenuating the second harmonic of the read signal; a second digital/analog converter for controlling the attenuating circuit; a low pass filter receiving an output from the attenuating circuit for pre-equalization of the read signal; a third digital/analog converter for setting a boost parameter of the low pass filter via a programmed digital boost value; a fourth digital/analog converter for setting a cut-off frequency parameter of the low pass filter via a programmed digital cut-off frequency value; a compensation stage for compensating an offset of an output of the low pass filter; a fifth digital/analog converter for controlling the compensation stage; a second adaptive filter for equalizing an output from the compensation stage; an analog-to-digital converter receiving an output from the second adaptive filter; a local voltage controlled oscillator for providing a sampling frequency to the analog-to-digital converter; a sixth digital/analog converter for synchronizing the local voltage controlled oscillator; and a post processing digital circuit receiving an output from the analog-to-digital converter and for generating digital control commands for the first, second, fifth and sixth digital-to-analog converters; wherein the programmed digital boost and cut-off frequency values for setting the boost and cut off frequency parameters of the first low pass filter are defined for each information medium as a function of instantaneous operating parameters of the second adaptive filter sensed during a scanning phase of the information medium.