T. Hamaguchi

The University of Tokyo, Tōkyō, Japan

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Publications (5)5.03 Total impact

  • T. Hamaguchi · H. Maeda · K. Usui · K. Shishida
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    ABSTRACT: We describe an alternating dc track servo pattern as a way to avoid magnetization imbalances within the position error signal (PES) regions of the media in perpendicular recording systems. A spin-stand was used to compare signal amplitude and medium noise between the alternating dc track servo pattern and a conventional dc-track servo pattern. The alternating dc track servo pattern improves the signal amplitude and decreases the residual noise. Therefore, the new servo pattern exhibits a superior signal-to-noise ratio of the PES regions.
    IEEE Transactions on Magnetics 11/2005; 41(10-41):2872 - 2874. DOI:10.1109/TMAG.2005.855300 · 1.39 Impact Factor
  • T Hamaguchi · H Maeda · K. Shishida
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    ABSTRACT: A perpendicular recording system can provide improved writing ability on high-coercivity media and stabilize high-density bits against the superparamagnetic effect. On the other hand, when bits are written on a perpendicular medium at low density, as is the case with the PES (position error signal) region of a conventional servo pattern, linearity in reading/writing operations is distorted, which are strongly affected by the regions of dc magnetization. This paper presents a way in reducing such distortion of characteristics of reading/writing processes using perpendicular media.
    Magnetics Conference, 2005. INTERMAG Asia 2005. Digests of the IEEE International; 05/2005
  • Takehiko Hamaguchi · Hideaki Maeda · Kazuhisa Shishida
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    ABSTRACT: We describe an advanced dc-free track code pattern that uses diphase code for a perpendicular recording. Track code error rates are compared between diphase code, dummy-bit code, and conventional dibit code. The diphase code improves writing ability during servo track writing and maintains equivalent medium noise. Therefore, the diphase code exhibits a superior track code error rate within a wide range of radius on experimental hard disk drives.
    IEEE Transactions on Magnetics 02/2005; 41(1-41):137 - 139. DOI:10.1109/TMAG.2004.832489 · 1.39 Impact Factor
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    ABSTRACT: A design methodology for reducing seeking noise in a hard disk drive has been developed. This method can optimize the seeking current according to a shock-response-spectrum analysis. It was verified experimentally that this method can reduce the seeking noise by about 4 dBA on average without increasing the seeking time.
    Microsystem Technologies 09/2003; 9(8):573-580. DOI:10.1007/s00542-003-0323-x · 0.88 Impact Factor
  • K. Yasuna · T. Yamaguchi · K. Shishida · T. Hamaguchi
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    ABSTRACT: A technique for evaluating track deviation in magnetic disk drives has been developed. The technique uses an external position sensor and an error cancellation sequence, and enables measurement of track-to-track spacing. The resolution of track position is less than 2 nm. The repeatability is less than 5 nm. The technique helps reveal track alignment error, which needs to be reduced to achieve over-100-KTPI recording
    IEEE Transactions on Magnetics 08/2001; 37(4-37):1881 - 1883. DOI:10.1109/20.950997 · 1.39 Impact Factor