DIFFERENTIATION-BASED WAVEFORM EQUALIZATION IN HIGH DENSITY DIGITAL MAGNETIC RECORDING.

Abstract

Differentiation-based waveform equalization was investigated to increase recording density in large capacity magnetic disk drives. This equalization not only slims isolated readback pulses but also reduces pulse asymmetry. The equalizer used in this study was composed of a transversal filter and a differentiator, and emphasizes the high band spectrum of the readback channel. When asymmetry in isolated pulses is negligible, which is typical of thin media in large capacity magnetic disk drives, a half-pulsewidth can be slimmed to nearly 0. 6 of the original width. Consequently, recording density can be increased 1. 5 to 2 times without increasing intersymbol interference. This equalization method is also effective for slimming asymmetrical isolated pulses. By optimizing the equalization constants, the half-width of isolated pulses can be slimmed to 0. 55 of the original width. This results in a remarkable reduction in intersymbol interference.