Write-read-write signal precompensation techniques for magnetic recording

Medium noise in magnetic recording has been shown to be caused in part by the magnetic microstructure of the medium, which is determined at the time of manufacture of the medium. Systems can be designed to exploit this spatial dependence to increase recording density. Signal precompensation to achieve this is described here using two possible models for medium noise: additive and multiplicative. Based upon recent experimental results, the multiplicative model should be the more realistic of the two models, and hence is discussed in more detail. The anticipated increase in performance is quantified in terms of the signals written on the medium and the noise power.