Methods and apparatus for performing high density

Abstract

Methods and apparatus are disclosed which utilize isotropic/perpendicular medium for performing high density digital magnetic recording. According to the preferred embodiment of the invention, the l's of a binary code are deeply imprinted on the medium by switching off the current in the winding of a magnetic ring head. The l's so imprinted on the medium are each represented by a copy of a part of the fringing field of the ring head. Each imprinted field has the appearance of a 'horseshoe' pattern of magnetization. During readback these imprinted patterns correlate extremely well with the sensitivity function (the fringing field) of the ring head/readback transducer. The invention utilizes this inherently present correlation, together with a combination of longitudinal and vertical recording techniques, to provide methods and apparatus well suited to locate signals buried in noise and yield improved overall readback performance in a high density environment. Additionally, following the imprint of each horseshoe, the preferred embodiment of the invention provides for the resumption of current flow, with opposite polarity, as the imprinted pattern(s) moves downstream. This technique continues the perpendicular magnetization at the trailing edge of a previously formed horseshoe pattern and fills voids in magnetization on the medium.