Fujitsu Corporation

Hideki Ohmori

Masahito Iwatsubo

Osamu Ikata

Shuichi Hashimoto

Masahide Kanegae

Masanori Ueda

Hiroyuki Tanaka

Yoshio Satoh

Isamu Tomita

Yoshiro Fujiwara

Masayuki Korikawa

Kazuhide Ohba

Nobuo Hirasawa

Toru Shinohara

Masao Kondou

Yoshihiro Hashimura

Kazushi Hashimoto

Hajime Miura

Takasi Watanabe

Kenji Fukayama

Tomoki Sugaya

Kensuke Miyagawa

Tsuneo Ohsugi

Saori Yokoyama

Katutoshi Asai

A thermal asperity detection method includes the steps of (a) converting an analog signal reproduced from a magnetic recording medium into a digital signal using an analog-to-digital converter, (b) detecting thermal asperity based on the digital signal, and (c) automatically recognizing and managing detection of the thermal asperity by the step (b) by firmware.

Thermal asperity detection method, thermal asperity compensation method,

A filter device includes at least two filter elements provided in a package, each of the filter elements passing only signals within a predetermined frequency band, the predetermined frequency bands of the filter elements having center frequencies which are distinct from each other. An input terminal is connected to and shared by respective inputs of the filter elements. An output terminal is connected to and shared by respective outputs of the filter elements.

Filter device and dual-band radio system in which the filter device is

A method is provided to adjust a bias current flowing through a magneto-resistive effect type magnetic head. An examining current is supplied to the magneto-resistive effect type magnetic head, and a voltage applied to a pair of terminals of the magneto-resistive effect type magnetic head is measured. In addition, a resistance of the magneto-resistive effect type magnetic head is calculated according to the examining current and the voltage, and an allowable range of the bias current flowing through the magneto-resistive effect type magnetic head is determined according to a relationship between a life time of the magneto-resistive effect type magnetic head examined in advance and the resistance of the magneto-resistive effect type magnetic head. An optimum bias current is determined within the allowable range in condition that a slice level margin is maximized.

Method and apparatus for adjusting a bias current of a magneto-resistive

Disclosed is a PRML regenerating apparatus for regenerating a signal read by a head from a storage medium. This PRML regenerating apparatus has a waveform equalizing circuit for waveform-equalizing the read signal, a maximum-likelihood decoder for maximum-likelihood-decoding, after obtaining a determination value by comparing the equalized output with upper and lower slice levels, this determination value and a control circuit for setting variable a distance between the upper slice level and the lower slice level of the maximum-likelihood decoder. The distance between the upper and lower slice levels can be thereby set variable in accordance with an equalization characteristic. A ternary determination circuit of the maximum-likelihood decoder is constructed of a memory for storing a correspondence table of the equalized output and the upper or lower slice level versus the determination result and the next upper or lower slice level. The ternary determination circuit can be thereby actualized with a simple configuration.

PRML regenerating apparatus having adjusted slice levels

An AGC circuit is used for read channels of a disk storage apparatus, by controlling a level of a reading output of a head to be kept constant. This AGC circuit has a gain control amplifier and a feedback circuit for digitally feeding back an output thereof. A maximum current value of a current type D/A converter is varied for every zone in zone bit recording. A gain adjusting time of the AGC circuit can be therefore minimized in each zone. A GAP length in the respective zones can be thereby reduced, and a storage capacity is increased. A maximum current value of the current type D/A converter is varied in a read/write area and a data surface servo area on a disk storage medium. It is therefore feasible to minimize the gain adjusting time of the AGC circuit in each of the servo area and the read/write area. The current type D/A converter is set so that a plus-side maximum current value is different from a minus-side maximum current value. The operation is therefore speeded up when increasing a gain, and the gain adjusting time of the AGC circuit can be minimized.

AGC circuit of disk storage apparatus

PRML regenerating apparatus

Disclosed are a partial-response record signal regenerating method of and an apparatus for regenerating a record signal of a data area which is read from a storage disc by use of an equalizing circuit after training a circuit constant of said equalizing circuit with a training signal of the record signal read from the storage disc. The record signal regenerating method comprises: a Viterbi decode step of Viterbi-decoding an output into which the record signal is equalized by the equalizing circuit; a decode step of converting an m-bit output which is Viterbi-decoded into n-bits (m&gt;n); and a synchronism detecting step of detecting the training signal from the m-bit output which is Viterbi-decoded and indicating a start of decoding the record signal of the data area. The record signal regenerating apparatus comprises: an equalizing circuit for equalizing the record signal by use of its circuit constant trained by a training signal recorded in front of a data area on the storage disc; a Viterbi decode circuit for Viterbi-decoding an output of the equalizing circuit; a decoder for converting an m-bit output which is Viterbi-decoded into n-bits (m&gt;n); and a synchronism detecting circuit for indicating a start of decoding of the decoder by detecting the training signal from the Viterbi-decoded m-bit output.

Method of and apparatus for regenerating partial-response record signal

A magnetic disk module adapted to be inserted in a data storing device body which is in use. The module includes two sets of disk drive units and printed wiring boards in one housing so that are disk drive unit or printed wiring board can be easily attached or detached in one set while the other set is in an operating state. The module includes a first connector attached to the disk drive unit, a second connector attached to the printed wiring board, a third connector at the rear end of the housing for plug-in connection to a connector of a data storing device body, a fourth connector arranged in the housing for plug-in connection to the first connector, and a fifth connector arranged in the housing for plug-in connection to the second connector.

Magnetic disk module

A processor of a drive unit positions a head to a designated cylinder position of a disk medium on the basis of a command notified from an upper controller through a data bus and amplifies a read signal by a read amplifier and, after that, transmits the amplified read signal to the upper controller through a read signal line. A data disconnecting circuit is provided for the data bus from an upper apparatus to the processor. The data disconnecting circuit switches the data bus to a disconnection state by a control signal which is generated from the upper apparatus during the data reading operation. When the control signal is interrupted by the end of the data reading operation, the data bus is returned to the connection state.

Method and apparatus for eliminating noises with a read operation of

A multilayer duplexer package is provided, which includes: two surface-acoustic-wave filter chips having different center pass band frequencies; and at least two phase matching circuits for matching the phase of one filter chip to that of the other filter chip, said phase matching circuits respectively comprising strip lines stacked one above another, and said strip lines each having a characteristic impedance higher than the characteristic impedance of an external circuit to be connected to the duplexer package.

Duplexer package

A voltage control oscillator which has an oscillator circuit comprising at least an inductive resonator, active element, and variable capacitance diode and externally applies a direct current control voltage to the variable capacitance diode through a bias circuit to change an oscillation frequency by altering a capacitance value of the variable capacitance diode with variations of the direct current voltage, comprising bias circuit is a low-pass filter comprising a resistor and a capacitor and the oscillation frequency is set higher than a cut-off frequency of the low-pass filter.

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Kawasaki, Japan

Hideki Ohmori