Piya Kovintavewat and Santi Koonkarnkhai

pp. 425 - 430

Abstract

A novel method for reducing the effect of a thermal asperity (TA) in perpendicular recording channels is proposed,
which consists of two channels running in parallel, one for the H(D) target and the other for the G(D)H(D) target equipped
with a bandpass filter G(D) = 1 – D²
. The Viterbi detector (VD) in the H(D) channel has a lower bit-error rate (BER) in the
absence of a TA, whereas that in the G(D)H(D) channel has a lower BER in the presence of a TA. Therefore, the overall
decoded bit stream is selected from these two VDs, depending on whether a TA is detected. Because the noise after G(D)
filtering is correlated, we also propose a noise predictor filter of the form P(D) = –0.5D²
 to whiten this correlated noise in a
per-survivor manner. Experimental results indicate that the proposed TA suppression method outperforms the existing
methods for all peak TA amplitudes.