Equalization techniques for high-density magnetic recording

The advent of digital computers spurred the development of magnetic tape and disk-drive storage systems capable of storing large amounts of digital information. Since the early development of such systems in the 1950s, we have experienced a phenomenal growth in the use of digital storage systems and an equally large increase in storage capacity and storage density. Over the past four decades, the major factor contributing to the large increases in storage density and capacity has been the continuous technological improvements in the design and development magnetic media and heads. As the storage densities increase, signal processing becomes an important tool in the reconstruction of the digital information in the readback process. We present a tutorial treatment of signal-processing techniques for combating intersymbol interference inherent in high-density digital magnetic recording systems. We focus primarily on magnetic disk systems. We observed that the optimum detector for the ISI-corrupted signal is a maximum-likelihood sequence detector (MLSD) that can be efficiently implemented by means of the Viterbi algorithm