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We propose a model for a magnetic recording channel to estimate the influences of the nonlinear distortion of an MR head on the performance of the PRML system, using a superposition of a magnetic field and a transfer curve obtained by a micro-magnetic model. A readback signal was simulated using a nonlinear model. The simulated signal was compared with an actual readback signal in the analysis of the isolated pulse, frequency response, and extracted dipulse response. We found that the nonlinear model represents actual MR head output satisfactorily, and that the performance of the PR4ML system was affected by the nonlinear distortion of the MR head for a 5% loss of the amplitude margin when the asymmetry was within 10%.

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 [[micro]meter] on the Co[Cr.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 [[micro]meter]. The error rate performance was tested using a PR4ML channel with write precompensation. At a data rate of 3.3 MB/s, a practical error rate of 9.0x[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 1.0x[10.sup.-14].

We developed an integrated-Viterbi-detector which can handle PRML and EPRML. Both PR4 and 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. Our 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.

A write frequency has been increasing by improvement of a write driver and a write head for higher transfer rate in hard disk drives. A certain method for high write frequency operation is to put a write driver chip on the suspension. We designed a chip-on-cable-patterned suspension (C-CAPS) that is an integrated wireless suspension with a write driver chip on. This paper describes the first observation of the effect on the chip-on-suspension in the write frequency and what type of the C-CAPS is suitable, especially relating to the location of a chip, for high performance hard disk drives. Next, we clarify characteristics of the C-CAPS, such as write current transition time, interface between the chip and disk, shock resistance, frequency response, thermal deformation due to temperature increase of the chip, and static attitude change due to bonding the chip. We conclude the C-CAPS contributes to increase a write frequency and the best location of a chip is on the tip of the load beam for high performance hard disk drives. Index Terms--Hard disk drive, suspension, head, slider, write driver, chip, write current transition time, resonant frequency, shock resistance, static attitude, thermal deformation, CAPS, flying height.