Analysis of Nonlinear Transition Shift and Write Precompensation in Perpendicular Recording Systems

Center for Magn. Recording Res., Univ. of California, La Jolla, CA, USA
IEEE Journal on Selected Areas in Communications (Impact Factor: 3.45). 03/2010; 28(2):158 - 166. DOI: 10.1109/JSAC.2010.100204
Source: IEEE Xplore


In high density perpendicular magnetic recording channels, nonlinear transition shift (NLTS) is one of the distortions that can degrade the system performance. Write precompensation is a standard method used to combat the negative effect of NLTS. In this paper, we present an analysis of the bit-error-rate (BER) for perpendicular recording systems with NLTS and write precompensation. Media jitter noise and additive white Gaussian noise are also considered in the model. A BER lower bound is derived, as well as a more easily computed estimate of the bound. The write precompensation values that numerically minimize the estimate of the BER lower bound prove to be very close to those found using Monte-Carlo channel simulation. We then apply these methods to the design of multilevel precompensation schemes, for which the optimization of precompensation values by Monte-Carlo channel simulation is computationally infeasible. The results show that for higher recording densities subject to increased ISI and noise, the use of more complex precompensation schemes does not significantly improve the system performance.

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    ABSTRACT: This chapter discusses several magnetic recording principles. The recording of magnetic information on a medium is based on specific magnetic grain properties. These magnetic particles have a preferred direction of magnetization (easy axis) in the absence of the external magnetic field. Modern recording media are based on perpendicular magnetic recording that is the easy axis is oriented perpendicular to the disk surface. The primary function of a perpendicular recording head is to achieve a high perpendicular magnetic field magnitude, localized in a small area (less than 100 nm in cross-track direction) using small power and dissipation. Recording head switching required for transition recording should be completed in 1 ns or less, as determined by the disk drive data rate. Magnetic data storage devices initially used inductive transducers for both the read and the write function. Initially recording heads had a ferrite core made from bulk material and actual wires to magnetize the core for writing and picking up the inductive signal when reading. A significant improvement was the step to integrate thin film heads that allowed shrinking of the head dimensions and in particular the read/write pole width and the write gap length to micrometer dimensions.
    No preview · Chapter · Dec 2011