This report shows the the performance comparison of the Partial Response Maximum-Likelihood (PRML) systems, PR4ML, EPR4ML and E^2PR4ML, for rate 11/12 Punctured Convolutional Code (PCC) and conventional 8/9 code. The bit error rate (BER) performances of both coded PRML systems are obtained by computer simulation. The relationship between the required SNR at the reading point to achieve a bit-error rate of 10^<-4>and the normalized linear density are also evaluated. The result shows that E^2PR4ML system for rate 11/12 PCC has an excellent performance at high liner densities.

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A punctured convolutional coded PR4ML system for digital magnetic recording applying a punctured method to the convolutional code and recording the punctured code sequences on two tracks is proposed. In this paper, the error rate performance of the proposed system is obtained by computer simulation taking account of the partial erasure which is one of nonlinear distortions at high densities and it is compared with that of a conventional INRZI coded PR4ML system. The results show that the proposed system is hardly affected by partial erasure and keeps good performance in high density recording. A bit error rate of 10^<-4> can be achieved with a SNR of about 8.8dB less than a conventional system at a normalized liner density of 3.

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The performance comparison of the various partial response maximum-likelihood (PRML) systems for high density magnetic recording using a double-layered perpendicular magnetic recording media and an MR head is studied. The bit-error rates of PR (1,1) ML, PR (1,2,1) ML, PR (1,3,1) ML, PR (1,2,2,1) ML and PR (1,3,3,1) ML systems for (1,7) RLL code and PR4ML, EPR4ML, E^2PR4ML and ME^2PR4ML systems for 8/9 code are obtained by computer simulation and are compared. Then, the relationships between the SNR improvement of these PRML sytems over PR4ML and the normalized liner density are evaluated. It is shown that PR (1,2,2,1) ML for (1,7) RLL code exhibits the best performance at high linear densities.

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Image compression has become an important technology for the transmission and storage of images. Fractal image coding is a novel compression method for greyscale images and it has become a focus of attention. Many improvements have been achieved regarding image compression methods. This report describes an attempt to apply fractal coding to contour detection, which is a new application. Dynamical systems in which parameters are fixed by self-similarity information in the compressed code are used in the proposed method. It is shown that the contours of some objects in a test image were detected well.

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Nonlinear transition shift (NLTS) in perpendicular magnetic recording was experimentally studied. The pseudo-random sequence analysis was utilized. A result showed that NLTS was several percent even at 318 kFRPI, or bit interval of 80nm, which agreed with a result of a computer simulation. Experiments of the precompensated write-current the NLTS acts to widen the shortest bit interval which is opposite to longitudinal recording. Pulse narrowing was also detected by the analysis.

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We present a set-partition of outputs set of the Extended PR channel which is suitable for high linear density recording. The set-partition provides that information bits are arranged in Euclidean distance order. The distances of three levels in the order are 4,8,and 16,respectively. Since the redundancy of the error correction code for the information bits depends on the distance, an efficient concatenated code is offered. Run-length of the set-partition and optimal signal format in a sector of magnetic storage disk are future study issues.

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We developed a new LSI system for digital VCR signal processing of 8mm camcorder. The use of analog LSIs has limited the low supply voltage design and low power consumption. By replacing most of VCR signal processing to digital LSIs and applying some new techniqes, we made it possible to reduce the supplied voltage and to cut the power consumption down to 50% of our conventional systems. As the result, since digital VCR processing system has much more compatibility with video memory systems, it became easier to apply digital memory features to camcorder models in most price ranges.

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