Dropout Compensation by Equalizer Selection and Kalman Filter-Based Timing Recovery

When occasional dropouts occur in magnetic tape recording systems because of defects and debris, the readback signal exhibits amplitude loss, pulse widening, and peak shifts, and the corresponding entire data block may be lost. In this paper, we develop a dropout compensation method that works in conjunction with the interpolated timing recovery method. In this method, we estimate the readback signal envelope and use it as a measure of the depth of a dropout. On the basis of the estimated envelope, an equalizer can be selected from a pretrained filter bank to transform the distorted transition response in a dropout to the desired partial response target. In addition, a Kalman filter-based scheme can be used to determine the phase and the frequency update gains in the timing recovery loop. We show that, by using Kalman filter-based timing recovery, more dropouts can be compensated