Reproduction of Digital Signals in Magnetic Recording: A Theoretical Study

摘要

Some fundamental aspects of the process of magnetic information storage aredescribed. The purpose of magnetic information storage is to accomplish a one to one correspondence between a time dependent signal that contains any type of information and that is available at a single position in space on one hand and a time independent spatial pattern of permanent magnetization on the recording medium on the other hand, and vice versa. Special attention is given to the read process in magnetic recording theory. The read process can be described by the quasi static approximation to the electromagnetic field equations. The basic relations for the quasi static magnetic field are presented. The integral relations of the Green type for the magnetic field strength and the magnetic flux density in the quasi static approximation are discussed. The way in which the quasi static magnetic field in multilayered structures can be calculated, is outlined. The reproduction process is analyzed in the two dimensional approximation. It is shown that the phenomenon of gap nulls is not restricted to an inductive ring head with a small gap, but that it also shows up when a single pole head is used. Geometries that markedly differ from the inductive ring and single pole heads are analyzed.