Hitachi, Ltd.

Yosuke Hori

Yasuhide Ouchi

Hideki Sawaguchi

Naoki Satoh

Naoki Sato

Seiichi Mita

Terumi Takashi

Yoshiju Watanabe

Shoichi Miyazawa

Akihiko Hirano

Ryushi Shimokawa

Toshihiro Nitta

Koji Shida

Hideki Miyasaka

Tomoaki Hirai

Satoshi Minoshima

Yutaka Okada

Hirotsugu Kojima

A signal processing circuit for a magnetic recording/reproducing apparatus, including at least an AGC, a PLL, a LPF, an equalizer circuit and a detection circuit, wherein a coefficient compensation circuit is formed by defining a constitution of the equalizer circuit, an error detection circuit is provided which operates by receiving input from the detection circuit, and the LSI is formed by a plurality of analog and digital chips, and the analog and digital chips are connected by current-output type D/A converters connected to at least the AGC and the PLL.

Signal processing circuit and information recording/reproducing apparatus using the same, and method for optimizing coefficients of equalizer circuit

A magnetic recording and reproduction apparatus, includes a circuit for changing a reference amplitude value of a Viterbi detector. The circuit is used to record and reproduce data with the reference amplitude value displaced from a reference value, thereby measuring the data error rate. Displacement of the reference amplitude from a reference value increases the data error rate, and therefore the data error rate can be measured within a short time. A data error rate with the reference amplitude equal to a reference value is estimated from the data error rate measurement, thereby making it possible to evaluate the degree of accuracy of a magnetic recording and reproduction apparatus. The data error rate is measured with the reference amplitude of the Viterbi detector displaced from a reference value while changing the equalization coefficient value of a waveform equalizer, the cut-off frequency of a low-pass filter and the write precompensation amount of a write precompensation circuit. In this way, the effect of the reproduction channel parameter or the write precompensation amount on the degree of accuracy of the magnetic recording and reproduction apparatus is evaluated, and the optimum value of the reproduction channel parameter or the write precompensation amount can thus be determined.

Magnetic recording and reproduction apparatus

A magnetic recording and reproduction apparatus: includes a circuit for changing a reference amplitude value of a Viterbi detector. The circuit is used to record and reproduce data with the reference amplitude value displaced from a reference value, thereby measuring the data error rate. Displacement of the reference amplitude from a reference value increases the data error rate, and therefore the data error rate can be measured within a short time. A data error rate with the reference amplitude equal to a reference value is estimated from the data error rate measurement, thereby making it possible to evaluate the degree of accuracy of a magnetic recording and reproduction apparatus. The data error rate is measured with the reference amplitude of the Viterbi detector displaced from a reference value while changing the equalization coefficient value of a waveform equalizer, the cut-off frequency of a low-pass filter and the write precompensation amount of a write precompensation circuit. In this way, the effect of the reproduction channel parameter or the write precompensation amount on the degree of accuracy of the magnetic recording and reproduction apparatus is evaluated, and the optimum value of the reproduction channel parameter or the write precompensation amount can thus be determined.

Magnetic recording and reproducing apparatus including a viterbi

Signal processing circuit and information recording/reproducing

A magnetic recording apparatus comprises: a magnetic recording medium for recording a binary signal; a magnetic head for detecting the binary signal; an amplifier for amplifying the binary signal detected by the magnetic head; a channel for outputting the amplifier binary signal in the form of a timing value sequence, the timing value sequence alternately providing positive and negative peak values following the rule of the binary signal a recorded in the recording medium; a temporary judging unit for judging a presently input timing value of the timing value sequence supplied from the channel as one of the positive peak value, the negative peak value, and an intermediate value, in accordance with the relationship with a preceding timing value temporarily judged as one of the positive and negative peak values; a final judging unit for finally setting the preceding timing value as one of the positive and negative peak values and the intermediate value, in accordance with the relationship with the presently input and temporarily judged timing value; a counter for counting the number of input bits of the timing value sequence; a unit for resetting the counter when the timing value temporarily judged as one of the positive and negative peak values is output; a register for storing a decoded binary bit value; and a unit for overwriting the bit value in the register at the bit position corresponding to the count of the counter.

Recording/reproducing apparatus with maximum likelihood sequence

In a phase discrimination signal processing system in the signal reproduction of a magnetic recording and reproducing apparatus, instead of differentiation of a reproduced signal, amplitude discrimination automatic equalization is effected for an isolated waveform at a phase discrimination point corresponding to an isolated magnetization reversal reproduced by a magnetic head such that an amplitude at each discrimination time other than a peak point is zero to effect phase discrimination of the signal waveform.

Magnetic recording and reproducing method using phase discrimination and

A nonlinear compensation A/D converting method and a circuit for compensating asymmetry of a reproduction signal waveform, so as not to deteriorate the performance of a discriminator even if there is a nonlinearity such that the amplitudes of the signal differ in dependence on the polarities of the waveforms like a reproduction waveform of an MR head are provided. Scales 1+ and 1- of an A/D converter are set to values which differ in dependence on the positive and negative polarities of the input signal, so that a nonlinear compensation which is suitable for a high accurate and high speed operation can be realized. Even an MR head in which the asymmetry between the upper and lower waveforms of the reproduction waveform is large can be used. A yield of the head can be improved.

Information processing apparatus for processing reproduction signal

A reproduction signal processing apparatus includes a memory circuit storing a predetermined pattern for deciding equalizing characteristics of an automatic equalizer in response to variation of a reproduction signal, a pattern converting circuit for converting the predetermined pattern outputted from the memory circuit into an equalization target pattern serving as a target of the equalization and correction by the automatic equalizer, an equalization error calculating circuit for producing an equalization error from the equalization target pattern and the equalization signal outputted from the automatic equalizer, and the automatic equalizer executing a partial response waveform process of the reproduction signal on the basis of the equalization error, for correcting the predetermined equalizing characteristics of the automatic equalizer by tracing the fluctuation of the reproduction signal. Thus, the equalization and correction tracing the variation of the equalizing characteristics of the automatic equalizer are executed, and also, the equalization and correction including the partial response waveform process are executed in the automatic equalizer.

Magnetic recording and reproducing apparatus, reproduction signal

A magnetic recording apparatus includes a magnetic recording medium for recording a binary signal; a magnetic head for detecting the binary signal; an amplifier for amplifying the binary signal detected by the magnetic head; a channel for outputting the amplified binary signal in the form of a timing value sequence, the timing value sequence alternatively providing positive and negative peak values following the rule of the binary signal that recorded in the recording medium; a temporary judging unit for judging a presently input timing value of the timing value sequence supplied from the channel as one of the positive peak value, in accordance with the relationship with a preceding timing value temporarily judged as one of the positive and negative peak values; a final judging unit for finally setting the preceding timing value as one of the positive and negative peak values and the intermediate value, in accordance with the relationship with the presently input and temporarily judged timing value; a counter for counting the number of input bits of the timing value sequence; a unit for resetting the counter when the timing value temporarily judged as one of the positive and negative peak values is output; a register for storing a decoded binary bit value; and a unit for overwriting the bit value in the register at the bit position corresponding to the count of the counter.

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Hiratsuka, Japan

Yosuke Hori