Hiroshi Mutoh

Viterbi detector including PRML and EPRML

The authors develop an integrated-Viterbi detector which can handle partial-response maximum-likelihood (PRML) and extended PRML (EPRML). Class 4 partial response (PR4) and extended PR4 (EPR4) equalization can be accepted according to the recording density. The EPRML performance is superior to that of PRML for a normalized recording density above 1.8, but inferior at lower densities. Experimental results agree with theoretical values and prove that the performance of this Viterbi detector is superior, by 8 dB, to that of conventional peak detectors when the normalized recording density is 2.7. >

5 Gb/in/sup 2/ recording demonstration with NiFe/Co/sub 90/Fe/sub 10/ spin-valve heads and low-noise thin-film disks

A high areal density of 5 Gb/in/sup 2/ (7.75 Mbit/mm/sup 2/) has been demonstrated with narrow track NiFe/Co/sub 90/Fe/sub 10/ spin-valve read heads on low-noise CoCrTaPt/CrMo-alloy thin-film disks. The MFM measurements clearly showed the write track width to be 1.2 /spl mu/m on the CoCr/sub 17/Pt/sub 5/Ta/sub 4/ thin-film media. This corresponds to 19.5 kTPI (768 track/mm) including a guard band of 0.1 /spl mu/m. The error rate performance was tested using a PR4ML channel with write precompensation. At a data rate of 33 MB/s, a practical error rate of 9.0/spl times/10/sup -6/ was obtained without error correction at a linear density as high as 257 kBPI (10.1 kbit/mm). At a linear density of 217 kBPI (8.5 kbit/mm), we obtained an error rate of less than 10/sup -8/ without error correction. With a 192-bit Reed-Solomon error correcting code, we can expected an error rate of 1.0/spl times/10/sup -14/.

The Effect Of MR Head Nonlinearity On MDFE And PRML Performance

The detection performance of multi-level decision feedback equalization (MDFE) and partial response with maximum likelihood detection (PRML) in the presence of magnetoresistive (MR) head nonlinearity is investigated through simulation. Two models are used to characterize the MR head nonlinearity: (1) a transfer function curve based on measurement and (2) a 3rd-order polynomial model. The results indicate that MDFE is more robust to MR head nonlinearity than PRML, especially to head saturation.

An experimental study of signal equalization for thin film heads

Signal processing for a thin film head, especially the influence of negative side-lobes, are discussed. Numerical analysis shows that a (1,7,2,3) code is superior to other run-legth-limited codes for well-balanced margins in a system featuring high density and a high transfer rate. Two techniques of reducing negative side-lobes were presented. One is a new equalizer, using pulse slimming and elimination of negative side-lobes. The other is an asymmetrical pole-face head. Experimental and theoretical results clarify that the two techniques are extremly effective in increasing the level margin.

Experimental Study of R/W Characteristics in Perpendicular Magnetic Recording Drives

In this paper, we will explain the nonlinear transition shift and write pre-compensation results in the fully functional PMR drives, and will discuss an approach to increase the density on hard disk drives using the PMR technology will be discussed.