Statistical analysis of signal and noise in magnetic recording

Abstract

The noise spectrum of a tape which is AC-erased is well formulated in the literature [1] . Though, a general theory based on classical statistics, which also delivers the power-spectral density for DC- and modulation noise is still lacking. In this paper we shall derive such a theory taking into account the statistics of all relevant parameters. First a new formulation is derived for the AC-erased case, which has a general character and includes the AC-erased noise spectrum of Mann [2]. Next a clustered medium is considered and a general expression for the DC-modulation noise is obtained. Furthermore, the harmonic magnetization in a clustered medium is examined, which reveals a power spectrum consisting of three fundamental contributions, the signal power, the background noise and the modulation sidebands. A similar result is obtained with a more realistic vectorial magnetization mode for the signal magnetization. The power spectrum for the case of AC-erased and DC-erased tape has been verified by experiment. Then, taking into account the tolerances of the parameters involved, there is still a discrepancy between the experimental and theoretical AC-erased tape noise power spectrum, which can only be explained in terms of particle interaction. The analysis is general in that it includes important mechanisms such as particle clusters and partial penetration of the signal into the layer. It can be adequately used in determining the S/N ratio in magnetic recording. The author intends to write a detailed paper on this subject for the IEEE Trans. on Magnetics.