Patent ID: 7394608
Filing Date: 2008-07-01
Classification: G11B

Abstract:
1. A method to read information encoded in a data storage medium, comprising the steps of: supplying a read channel comprising an analog to digital converter, an upsampler interconnected with said analog to digital converter, an interpolator interconnected with said upsampler, a fractionally-spaced equalizer interconnected with said interpolator, a gain control module interconnected with said fractionally-spaced equalizer, a sequence detector interconnected with said gain control module, a timing control circuit interconnected with said sequence detector and with said interpolator; reading a data track written to a data storage medium to form an analog signal, wherein said data track comprises information encoded at a first rate; asynchronously sampling at a fixed sampling rate said analog signal to form sampled signals; upsampling in the asynchronous domain at an upsampling rate, wherein said upsampling rate is greater than said first rate; forming interpolated samples; providing said interpolated samples to said fractionally-spaced equalizer at an interpolation rate, wherein said interpolation rate is greater than said first rate; forming synchronous, equalized samples at an equalization rate, wherein said equalization rate is less than said interpolation rate; adjusting the gain of said equalized samples; generating a timing signal; providing said timing signal to said interpolator; generating an equalizer error signal; providing said equalizer error signal to said fractionally-spaced equalizer; detecting data symbols representing a maximum likelihood sequence estimate using said gain-adjusted, synchronous, equalized samples, generating signal estimates formed by decisions from said sequence detector; wherein said generating an equalizer error signal step further comprises generating an equalizer error signal comprising the difference between said signal estimates and a delayed equalized signal, before gain control.