A Thermal Asperity Detection and Correction Algorithm for Perpendicular Magnetic Recording Channels

Abstract

The thermal asperity (TA) defect resulting from the collision between an asperity and the magnetoresistive (MR) read head can distort the readback signal to the extent of causing possible sector read failure. This paper presents a new TA detection and correction algorithm for perpendicular magnetic recording channels.  The proposed algorithm consists of two channels running in parallel, one for the H1(D) target, and the other for the H2(D) target equipped with a bandpass filter 1 - D2, where the H2(D) target is directly designed in the presence of a TA.  The Viterbi detector (VD) in the H1(D) channel has a lower bit-error rate (BER) in the absence of a TA, whereas that in the H2(D) channel has a lower BER in the presence of a TA. Thus, the overall decoded bit stream is selected from these two VDs, depending on whether a TA is detected. Results indicate that the proposed algorithm yields lower BER than the existing one, and is robust to large peak TA amplitudes.

Keywords : Bandpass Filter / Perpendicular Magnetic Recording / Target and Equalizer Design / Thermal Asperity