Adaptive equalization in magnetic-disk storage channels

Abstract

The use of adaptive equalization to increase storage density is discussed. Adaptive equalization is attractive since it permits a significant reduction in manufacturing costs by allowing a greater component yield due to relaxed tolerances and also permits a reduction in servicing costs because of a reduced need for fine-tuning on the customer's premises. The differences between data storage and data transmission channels are examined. The storage channel's important signal-processing characteristics are described, covering read and write processes, detection methods, and various types of distortion that can occur in storage channels. The use of signal-to-noise ratio as a performance measure is considered. Equalization methods for peak detection and for sampling detection are discussed. Gains in both linear and areal (track) density are addressed. Some of the basic performance advantages of using adaptive equalization are illustrated. The future of communication technology in storage systems is assessed.