Modulation and detection for digital magnetic recording
In this dissertation, we apply the principles of communication theory to digital magnetic recording channels in order to achieve more reliable and higher density storage systems. In Chapter 1, we give an overview of existing signal processing techniques and show the relevance of this dissertation to these techniques. In Chapter 2, the computational cut-off rate of a (d, k) input constrained discrete memoryless channel is described. This cut-off rate is used to find the gain in signal-to-noise ratio that can be achieved by the use of soft decision information. In Chapter 3, feed-forward timing recovery for recording channels that use sampling detection techniques is proposed. The performance of these timing loops is investigated as a function of both the recording density and the input signal-to-noise ratio. This timing recovery technique was found to be attractive for high density recording channels. In Chapter 4, the design and performance of non-uniformly spaced tap-delay-line equalizers is described and it shown that this structure performs better than the existing tap-delay-line equalizer structures. In Chapter 5, the efficient performance evaluation of intersymbol interference channels in the presence of additive white Gaussian noise is described. An algorithm is introduced to compute the minimum Euclidean free distance of the intersymbol interference channel very efficiently. Finally, in Chapter 6, we summarize the results of each chapter and present directions for future research.