Fujitsu Corporation

Yoshitaka Nakata

Masaru Sawada

Tsunehiko Moriuchi

Koji Horibe

Hideaki Tanishima

Kenichi Yamakura

Manabu Nakano

Tsuyoshi Tomita

Fumiaki Uematsu

Shigetaka Asano

A signal processor used to process an analog read signal representing data stored on a magnetic disk allows for a faster read operation without requiring an increase in its circuit area or buffer memory space. The signal processor includes a decision feedback equalizer which selectively provides a feedback signal added to a read signal in reproducing data read from a storage medium. The signal processor also performs error correction. In performing error correction, the load of the error correcting process is detected and the processing speed is altered depending upon the detected load.

Signal processor having feedback loop control for decision feedback equalizer

A semiconductor circuit includes a decision feedback equalizer (DFE) for waveform-equalizing an input signal and generating a waveform-equalized input signal. The DFE compares the waveform-equalized signal with a predetermined reference voltage to generate a decision signal having first and second decision values and an error signal which lies between the waveform-equalized signal and the decision signal. A dispersion value calculator is connected to the DFE, calculates first and second dispersion values of the first and second decision values of the decision signal using the error signal, and produces a compensation signal using the first and second dispersion values. An asymmetry compensator is connected to the DFE and the dispersion value calculator. The asymmetry compensator receives the input signal and corrects an asymmetry in the input signal in accordance with the compensation signal and supplies the corrected input signal to the DFE. The semiconductor device may be used in a hard disk control circuit.

Semiconductor device with decision feedback equalizer

A servo controller for correcting a read position of a head when reading data recorded on a recording medium. In accordance with the amplitude ratio of data signals read from each segment of a servo section defined on a recording medium, the servo controller generates an AGC signal corresponding to the next segment before reading the next segment. The data signal read from a phase detection segment of the servo section is amplified to an amplitude greater than the predetermined determination range. The amplified data signal is converted to a two-value digital signal in accordance with the determination range. The phase used during servo control is calculated in accordance with the digital signal.

Servo controller and servo control method

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Kasugai, Japan

Yoshitaka Nakata