Media selection for high density recording channels

Abstract

The implementation of high density partial response channels in disk drives has been hampered by nonlinear interactions between -transitions occurring in the write process. It is shown that the degree of nonlinearity is not characterized by the density relative to the isolated transition pulse width, rather by the transition spacing in relation to the transition width. Factors that determine the transition width are examined. In particular, the potential gains from using low moment media are investigated. A nonlinear model of the disk channel is discussed. The dependence of partial response signaling on linear superposition is discussed. Eye patterns are shown revealing the effects of nonlinearites on a partial response system.

Performance comparison of various PRML systems in high-density recording

“…The latter includes nonlinear bit shift, in which the magnetization transition is shifted depending on the recorded data, and partial erasure, in which neighboring zigzag magnetization transitions overlap, partially erasing the magnetization and causing a level degradation of the playback signal equivalent to reduction of the track width [2].…”

Soft-decision decoding of MTR codes over magnetic recording channels

“…U slučaju dve tranzicije aproksimativno se može reći da se amplitude odziva smanjuju za isti iznos, dok se u slučaju tri i više uzastopnih tranzicija situacija komplikuje. Ovaj efekat poznat je i kao delimično brisanje podataka [95] i [96]. Dodatna nelinearnost u procesu zapisivanja podataka nastaje usled uticaja magnetskog polja susednih namagnetisanih domena.…”

Nonlinear equalization for data storage channels

“…Transition noise, which is thought to originate from the zigzag nature of magnetic flux transitions, is a dominant source of noise in the medium [15, 1, 3, 81. At high linear density, adjacent magnetic transitions iteract with one another causing the channel to deviate from the conventional linear superposition model [5,6,3,18,201. So it is important to design the data recovery scheme which can operate under such channel distortions and noises.…”