Development of Signal Processing Systems for Digital Recording

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The basic concepts for the imformation density improvements in recording codes are summarized as follows:(1) to include DC-free property in order to restrict cross-talk and dc wandering, (2) to set T_<min> as large as possible in order to reduce the influence of intersymbol interference, where T_<min> is the time separation between two successive polarity changes in recording waveform, (3) to incease channel capacity as a function of several constaint parameters with respect to system design.Although a lot of recording codes are already proposed in this respect, there have been few publications with classification of the code. We introduced the finite automaton model as a useful tool for theoretical description of the coding rule and for facilitation of performance comparison among various proposed codes.FM code, one of the most famous and powerful codes, and its family codes have been investigateds to obtain fundamental insights for systematization of recording codes. It turns out that some conventional codes are identified with FM family codes.The reproduction process of signals in digital recording systems is not required to be a reciprocal function of recording process. For this reason, we adopted Partial Response(PR) systems for equalizing the detected signal and Viterbi algorithm in stead of bit-by-bit decoding method. We also assumed additive noise to be colored. As the results, significant improvements on both effective signal-to-noise ratio and bit error rate are performed.