Fujitsu Corporation

Toshiba Storage Device Corporation

Hiroaki Ueno

Hidekazu Shibasaki

Hitoshi Kanai

Takao Koshikawa

Tadashi Nakamura

Isamu Tomita

Kazuhito Ichihara

Toshinori Hoshino

Ken Yakuwa

According to an aspect of an embodiment, a storage apparatus has a storage for storing a plurality of compensation values in association with a plurality of bit sequence patterns, a head for writing data into a medium and a controller for controlling the apparatus and driving the head, the controller determining whether to use one of the compensation values to drive the head to write an instantaneous data bit in dependence upon the immediate preceding data bits in reference to the bit sequence patterns.

Storage apparatus and method for processing recording compensation

A nonlinearity measuring method capable of measuring NLTS with a higher precision while taking the state of magnetization inversion of a preceding bit string into consideration. A constitution includes a first measuring section measuring a first predetermined higher harmonic component from a regenerated signal of the reference signal magnetically recorded on a medium, a second measuring section measuring a second predetermined higher harmonic component from regenerated signals with respect to plural kinds of signals to be measured magnetically recorded on the medium, and a calculating section calculating NLTS from the first component and the second component corresponding to each of the signals, wherein each of plural kinds of signals to be measured includes a magnetization inversion pattern string Ppreceding the objective bit to be measured of NLTS; thereby NLTS depending on the string Pcan be quantitatively measured easily.

Nonlinearity measuring method, nonlinearity measuring unit, magnetic recording/regenerating unit and LSI for magnetic recording/regenerating

Data is read out from a disk in which the data is recorded in the perpendicular magnetic recording system by a head, amplified by a head preamplifier, and signal-processed by a read channel LSI. A read-out processing unit of a HDD controller sends out signals processed by the read channel LSI as an output of the perpendicular magnetic recording system. Further, a cut-off frequency controlling unit of the HDD controller determines a cut-off frequency of a high-pass filter of the head preamplifier based on a data transfer rate read out by the read-out processing unit, controls a cut-off frequency changing unit, and changes the value of the cut-off frequency.

Magnetic recording/reproducing apparatus and magnetic recording/reproducing method

Method of accurately measuring various kinds of non-linear transition shifts (NLTSs) in the magnetic recording/reproduction using an MR-type reproducing head is provided. According to the method, the data of a reference bit-string pattern are sent, as reference signals, to a magnetic diskvia a head ICand a magnetic headso as to be magnetically recorded. A first predetermined harmonic component Vnref is measured from the reproduced signals of the record data detected by the magnetic heada bit-string pattern is selected from plural kinds of predetermined bit-string patterns, the data of the selected bit-string pattern are sent, as to-be-measured signals, to the magnetic diska second predetermined harmonic component Vnpat is measured from the reproduced signals, and the NLTS is calculated from Vnref and Vnpat.

Method of measuring non-linearity in magnetic recording/reproduction, device for magnetic recording/reproduction and LSI for magnetic recording reproduction

A magnetic recording and/or reproducing apparatus includes an equalization section for equalizing a signal sequence which is reproduced from a magnetic recording medium and outputting an equalized waveform, and a conversion section for converting the equalized waveform into a maximum likelihood sequence by carrying out metric calculation based on average values of the equalized waveform.

Magnetic recording and/ or reproducing apparatus

An error propagation detection method and apparatus for use in decision feedback equalization type detection is disclosed, with which it is possible to detect error propagation even when a specific code conversion rule is satisfied in an MDFE system. If the input signal of a comparative decider be a binary signal a(k) expressed as &plusmn;1, an error signal ev(k) expressed by ev(k)&equals;&lsqb;y(k)&minus;Ideal y(k)&rsqb; sign&lsqb;a(k)&rsqb; is determined using a(k&minus;1)&ne;a(k&plus;1) as an error computation condition. The error signal ev(k) thus determined is checked to see whether it exceeds a specific value. If so, the slice level of the comparative decider is controlled to a corresponding offset value.

Error propagation detection and control method, and memory device using the same

The present invention provides an error propagation control method and device for effectively performing error propagation control in an M3DFE system. An error propagation detection section ( ) is provided at each one of a first multi-level decision feedback path ( ) and a second multi-level decision feedback path ( ), and a control section ( ) is also provided so that error propagation control of a best path is performed at an erasure end point using the error propagation detection result of the best path. Since error propagation control of the best path is performed, effective error propagation control, even for M3DFE, can be implemented.

Error propagation control method and device based on multi-level decision feedback equalization

An error propagation control method and a recording/reproducing device which uses the method in a system which makes use of MDFE are disclosed. In the error propagation control method in accordance with multi-level decision feedback equalization in which the input to the detector is fed back to the input side via the feedback filter and the difference between the input signal and the feedback signal is input to the detector, the error propagation state is detected based on the output of the detector. Based on the error propagation detection result, a predetermined offset is added to the slice level of the detector, DC offset is added to the DC level of the input signal of the detector, or a sign of the tap of the feedback filter is reversed.

Error propagation control method in decision feedback equalization and magnetic recording/reproducing device

When a pin layer magnetic field offset judgment unit judges that a magnetic field in a pin layer of a spin valve head through which a sense current flows in the interference direction has been deviated from a normal direction, a recovery processing unit allows a recovery from the abnormality arising from the magnetic field offset. For example, the direction of the sense current is switched from the interference direction to the assist direction, and the sense current larger than that upon the ordinary reading action is allowed to flow so that the temperature of an antiferromagnetic layer exceeds the blocking temperature, whereby the direction of the magnetic field in the pin layer is modified to the normal direction by the action of a magnetic field generated from the sense current. After the modification, the sense current is returned to have its ordinary value in the interference direction.

Apparatus for recognizing spin valve head failure due to pin layer magnetic field offset

A write signal is examined so as to recognize occurrence of magnetization reversal for a first bit to be recorded, a second bit preceding the first bit and a third bit preceding the second bit. A write signal reversal for the first bit is delayed by a first delay when the second bit has an associated write signal reversal and when the third bit does not have an associated write signal reversal. A write signal reversal for the first bit is delayed by a second delay set to be smaller than the first delay, when the third bit has an associated write signal reversal and when the second bit has an associated write signal reversal, and a write signal reversal for the first bit is delayed by a third delay set to be smaller than the second delay, when the third bit has an associated write signal reversal and when the first bit does not have an associated write signal reversal.

Write compensation method and magnetic disk apparatus adapted for

A signal reproducing circuit includes first power supply lines having different potentials, a magneto-resistive effect head having one end thereof coupled to the first power supply line, for reproducing data recorded on a magnetic recording medium in a read operation, and a first constant current source coupled between another end of the magneto-resistive effect head and the second power supply line, for supplying the magneto-resistive effect head with a sense current in the read operaion. Also included are first and second transistors having collectors thereof coupled to the first power supply line, respectively, and responsive to voltage signals obtained from the one end and the other end of the magneto-resistive effect head. Second and third constant current sources are coupled between each emitter of the first and the second transistors and the second power supply line, respectively, for supplying the first and the second transistors with a first predetermined constant current, respectively, in the read operation. Fourth and fifth constant current sources are provided between each emitter of the first and the second transistors, respectively, and the second power supply line for increasing the emiter curents of the first and the second transistors to a second predetermined constant current during a predetermined period in a transition from a write state to a read state.

Signal reproducing circuit for magneto-resistive head including control

A signal reproducing circuit for a magneto-resistive effect head includes a constant current source for supplying a sense current to an MR head in a read state, first constant current sources for supplying first constant currents to a pair of reproduction transistors in the read state, and a capacitor connected between the emitters of the transistors. Furthermore, second constant current sources for supplying second constant currents are connected in parallel with the first constant current sources. Control is given so that when switching an idle state to the read state is commanded, the second constant current sources remain on for a given period of time. Owing to this circuitry, a transient period during which the idle state is switched to the read state or a transient period during which heads are switched in the read state can be shortened to a great extent. Consequently, superposition of an unwanted offset component on a reproduced signal can be suppressed, and a loss in data-handling capacity can be minimized.

Signal reproducing circuit adapted to head utilizing magneto-resistive

The present invention relates to a signal reproducing method and a signal reproducing apparatus for reproducing a signal recorded by a high-density recording. The invention avoids deteriorating the performance of an ML detector while suppressing the equalization loss and the correlation noise. The signal reproducing method includes steps of generating a first signal using a first selected number of convolutions, generating a second signal using a second selected number of convolutions, and combining the first and second signals to identify the information in the input signal. The first and second signals can be processed by adding or subtracting the first and second signals, depending on the circuit configuration. With this invention, the number of convolution steps is reduced, and it is possible to reduce equalization loss and correlation noise using circuits having a small circuit scale. When applied to a disk drive, it is possible to improve reliability, reduce circuit scale and reduce the size and weight of the drive. It is also possible to obtain a high-density recording due to the reduced error rate realized by this invention.

Signal reproducing method and apparatus

A signal reproducing circuit includes a magneto-resistive effect head having one end thereof coupled to a first power supply line, for reproducing data recorded on a magnetic recording medium in a read operation. A first constant current source is coupled between another end of the head and a second power supply line, for supplying the head with a sense current in the read operation. First and second transistors have collectors thereof coupled to the first power supply line, and are responsive to voltage signals obtained from both ends of the head, respectively. Second and third constant current sources are coupled between each emitter of the first and second transistors and the second power supply line, respectively, for supplying the first and second transistors with a predetermined constant current in the read operation. A capacitor is connected between each emitter of the first and second transistors. A control circuit responsive to a read/write control signal controls respective ON/OFF timings of the first to third constant current sources. The control means controls at least one signal reproducing circuit portion corresponding to nonselected heads to be brought to a read state when a signal reproducing circuit portion corresponding to a selected head is in a write state.

Signal reproducing circuit adapted for head utilizing magneto-resistive

A decision slice setting unit of a 2-input judging unit has two coordinates (A) and (B) to be judged as -1 and two coordinates (C) and (D) to be judged as +1 into which input coordinates (f, g) can be set in a noiseless state. A straight line which passes through an origin and is parallel with each of a straight line connecting the two coordinates (A) and (B) to be judged as -1 and a straight line connecting the two coordinates (C) and (D) to be judged as +1 is set as a decision slice.

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Kawasaki, Japan

Hiroaki Ueno