S. Fukuda

11.5 Gb/in/sup 2/ recording using spin-valve heads in tape systems

We have investigated recording at densities higher than 4.5 Gb/in/sup 2/ in tape systems using spin-valve heads. We report the signal-to-noise ratio at areal recording densities of 4.5 Gb/in/sup 2/ and 11.5 Gb/in/sup 2/ on low-noise obliquely metal evaporated (ME) tapes. Also, we studied an electrostatic discharge failure of giant magnetoresistive heads on ME tape. The results indicate the feasibility of an areal density of 11.5 Gb/in/sup 2/ in a helical-scan tape system.

8/10 modulation codes for digital magnetic recording

It is difficult to record DC and low-frequency signals with the magnetic recording method. Furthermore, in high-density magnetic recording, the signal-to-noise ratio and the high-frequency output level are low and low-frequency crosstalk noise from the adjacent tracks is relatively high. A modulation code for high-density digital magnetic recording must have a large Tw and a DC-free characteristic. When we developed the R-DAT system, we developed two run-length limited 8/10 conversion rate modulation codes for use with the R-DAT. This paper discusses various possible modulation codes and confirms the superiority of one particular 8/10 modulation code.

High density digital magnetic recording using class I partial response and 8-10 block code

Improvements in readback heads and tapes have brought a readback-signal amplitude at a wavelength of 0.33 /spl mu/m 15 dB higher than that obtainable by a commercial digital data storage (DDS) system. An investigation to determine the most effective channel for the newest heads and tapes established that a class I partial response channel combined with DC-free 8-10 block code and maximum likelihood detection was optimum. Based on this channel and these heads and tapes, the DDS3 format was derived. It has an areal density of 530 Gb/m/sup 2/ and the linear density of 4.8 Mb/m.

Recording over 15 ktpi using multichannel heads in a tape system

In magnetic recording systems, it has been reported that sufficient signal-to-noise ratio (SNR) was obtained with a narrow track width, using a spin-valve head and metal-evaporated tape. In order to apply this to a helical-scan tape system, techniques for writing narrow tracks and reading them exactly were required. However, the degree of mechanical accuracy demanded was too high to realize. With this in mind, we have developed multichannel heads which can write and read certain tracks with a single scan, as well as a nontracking technique removing the need for such precise mechanical accuracy. A prototype tape drive employing these techniques was developed, and a track density exceeding 15 ktpi was achieved.

Track profile of MR head and its performance in a helical scan tape system

The MR head is being studied for use in helical-scan guardband-less tape systems. These systems need a read head with a wider track width than track pitch, so the track profile of the head is important. We analyzed the track profile of MR heads, and found that fluctuations in the reading signal are not an issue. We then mounted the head on a tape-streamer drive and measured the SNR. We found that the MR head provided an SNR which makes it possible to double the areal density with a margin more than 6 dB over that of an inductive head.

A narrower side erase band for use with helical scan tape systems

The MFM technique is very useful to measure the side erase band. MFM images were processed by FFT to measure the side erase band width and effective track width. Compared with the electromagnetic properties produced using the MR head, the measuring point is defined on FFT processed data. Mrt of the tapes (thickness of magnetic layer), type of recording head and recording frequencies were varied for the sample tapes. The track width of low Mrt tapes showed good stability in different combinations of recording frequency. The side erase band width was reduced when a trimmed MIG head was used. The influence of the recording current for the side erase band was negligible.

A new digital PLL for the Class I partial response channel

A digital PLL (DPLL) for using the class I partial response (PR1) channel was developed as part of a PR1-channel decoder LSI for a digital data storage III system. As a channel clock generator of this DPLL, a ring oscillator whose period can be controlled by changing its inverter number was employed. An analog-to-digital converter for sampling the readback signal was placed in the main loop of the DPLL and was driven by the reconstructed channel clock, so no master clock is needed. This DPLL can generate a channel clock of 50 MHz.

Recording characteristics at a channel rate over 300 mb/s in a helical-scan tape system

Recording characteristics at high-linear density were investigated using a spin-stand tape tester. Low-noise metal obliquely evaporated tape with a 40-nm magnetic layer was used. Read signal level and nonlinear transition shift of a thin-film head was compared with that of a metal-in-gap head. A prototype helical-scan tape drive with a thin-film head and a giant magnetoresistive head was developed to investigate the recording characteristics at channel rates over 300 Mb/s. A sufficient signal-to-noise ratio of 18 dB was obtained at a channel rate of 300 Mb/s with a read track width of 0.8 /spl mu/m and a linear density of 376 kFRPI.

An adaptive equalizer for the partial response Class I channel used by DDS3

A channel decoder IC for the DDS3 format has been developed. A digital PLL, an equalizer with a digital adaptive transversal filter, and a parallel Viterbi algorithm decoder were built into this IC. Minimizing the linear equalization error contributes to improving the detection signal-to-noise ratio. An adaptive equalizer with 22 taps was found to provide a good trade-off between performance and complexity. The detection error rate was reduced by approximately a factor of 10 by the adaptive equalizer.

A recording at a channel rate of 200 Mbps in helical tape systems

Summary form only given. We have reported a helical-scan tape system using MR heads as read heads. In this work, we have studied a tape recording at a channel rate of 200 Mbps, which is about double that of the current recording tape-streamer. By using MR heads and low noise ME tape, we have improved the performance of the CNR of the high clock-rate read channel. The impedance noise spectrum of the MR head is flat. The media noise is dominant in the total noise. The power of the media noise is kept constant at various recording rate.