Baseline Popping Detection and Correction Algorithms for Perpendicular Magnetic Recording System

Abstract

Hard disk drives (HDDs) employ the magneto-resistive (MR) head to sense the change in magnetic flux via the transitions of magnetization pattern, resulting in a readback signal. Thus, head instability plays an important role on the reliability of HDDs because it can deteriorate the system performance considerably. Baseline popping (BLP) is one of the crucial problems caused by the head instability, whose effect can distort the readback signal to the extent of causing a sector read failure. This paper proposes three BLP detection and correction algorithms for a perpendicular magnetic recording (PMR) system. Specifically, to suppress the BLP effect experienced in the readback signal, the first algorithm is based on an averaging filter and a threshold detector; the second one relies on the estimated BLP signal obtained from a linear curve fitting technique; and finally the third one uses two sequence detectors running in parallel. Experimental results indicate that the third algorithm performs better than the other schemes because it can detect and correct the BLP better than the others, especially when the peak BLP amplitude is large.