Hitachi, Ltd.

Hitachi Global Storage Technologies Japan, Ltd.

Hitachi Global Storage Technologies Netherlands B.v.

Hgst Netherlands, B.v.

Hitachi Global Storage Technologies

Hideki Sawaguchi

Yasutaka Nishida

Hisashi Takano

Takehiko Hamaguchi

Seiichi Mita

Yasuhide Ouchi

Atsushi Nakamura

Hiroshi Ide

Hiroyuki Tsuchinaga

Futoshi Tomiyama

Naoki Sato

Naoya Kobayashi

Yosuke Hori

Masafumi Mochizuki

Masaharu Kondo

Shaohua Yang

Richard Leo Galbraith

Terumi Takashi

Yuan Xing Lee

Yohji Maruyama

Travis Roger Oenning

Jongseung Park

Ksenija Lakovic

Toru Matsushita

Bruce Alexander Wilson

Mikio Suzuki

Naoki Satoh

Masuo Umemoto

Akihiko Hirano

Hirotsugu Kojima

Takashi Moriyasu

Mario Blaum

Masaaki Futamoto

Yoshibumi Matsuda

Nobuyuki Inaba

Kenji Mori

Morishi Izumita

Kyo Akagi

Takeshi Nakao

Hajime Aoi

Masao Hotta

Yoshinori Miyamura

Fumio Kugiya

Hirotsugu Fukuoka

Yutaka Okada

Takayuki Munemoto

Tokuho Takagaki

Hiroko Sukeda

Wataru Sakurai

Masaharu Kondou

Alexander Kuznetsov

Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Decoding techniques for correcting errors using soft information

To effectively suppress a signal in a low frequency region in which the medium noise and the signal distortion are concentrated, and in order to effectively utilize a detected component of the reproduced signal in the low frequency region, a target of partial response equalization to the perpendicularly recorded/reproduced signal is set so that the low-frequency component around the direct current is suppressed to a regulated quantity for both the effective suppression and the effective utilization. Accordingly, a maximum-likelihood decoding process is carried out through the target of partial response equalization. Reliability of data detection is made higher and a signal-to-noise ratio is improved, so that the noise from the recording medium can be reduced more and it is possible to provide a high-density magnetic recording/reproducing apparatus.

Apparatus, signal-processing circuit and device for magnetic recording system

An efficient encoding method for error correction coding for recording/reproducing information in a high-density magnetic recording/reproduction apparatus. Based upon the principle of Turbo coding for random error-correction a practical encoding method is provided for preventing the propagation of code errors from being caused by the failure of the error correction due to burst signal errors existing on actual reproduced signal and recovering reliable code data from this. An information code sequence is divided in units of code block and the random error-correction coding is applied to an individual code block. Concatenated coding with hard-decision error-correction code for compensating a burst error is subsequently applied. This allows the encoding method to reduce the decoding time delay, or latency, in iterative decoding for the error-correction thereby achieving high-speed error correction.

Recording format for information date, information recording/reproducing cording circuit

In a method of servo writing of a magnetic recording system and the magnetic recording system, the signal is recorded in a dummy area with a higher recording density than the burst signal. Also, the maximum bit length of the burst area is shortened as compared with the maximum bit length of the data area. A servo control method for perpendicular recording similar to that for longitudinal recording can be used to reduce the development cost. The anti-signal decay performance is also improved. Further, since the variations of the burst signal along the track width is suppressed, the positioning accuracy is improved. These effects combine to produce a reliable magnetic recording system of large capacity.

Method of servo writing for magnetic recording system, magnetic recording system

An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.

Reduced complexity error correction encoding techniques

A magnetic disk apparatus including: a disk holding data as magnetic information on a magnetic recording film; a head to perform writing and reading of the magnetic information; a rotary actuator to move the head in a radial direction of the disk; plural heat elements in the head to locally heat the disk; a write element in the head to apply a magnetic field to the disk; and means for selecting at least one heat element from the plural heat elements, wherein the means for selecting the heat element selects at least one heat element from the plural heat elements so as to bring a center line of an area heated by the heat element and a center line of the position of the magnetic field generated by the write element into approximate correspondence, in correspondence with a relative angle between the head and a direction of movement of the disk.

Magnetic disk apparatus having an adjustable mechanism to compensate write or heat element for off-tracking position with yaw angle

An efficient encoding method is provided for error correction coding in high density magnetic recording/reproducing apparatus. A first encoding circuit applies a first error correction coding to the information code sequence and generates an error-correction code sequence. A concatenated encoder is used to divide the plural code sequence blocks having predetermined lengths. The concatenated encoder also executes a second error-correction coding for each code sequence block and generates a second redundant code sequence. A code switch is used to output the plural code sequence blocks and the second redundant code sequence alternatively in order to generate information code sequence that is comprised of the plural code sequence blocks.

Embodiment of the invention is to make the number of interleave sequences and the number of redundant bits as small as possible without increasing the number of bits per symbol so much. By encoding data into an error-correcting code by using an algebraic geometric code consisting of an algebraic curve surface having a genus g over a projective plane P(GF()), where m is a positive integer, the code up to a length of 22g is constructed. In particular, by using a 'Fermat code,' a version of the algebraic geometric code, consisting of a Fermat curve 'C: X+Y+Z=0' over the P(GF(2)), where (m, L)=(5, 11), 4-Kbyte data constituting one sector can be encoded into the code made up of 10-bit symbols.

Recording/regenerating device, method of encoding error correction, method of recording data

In the present invention, by making the width of the write element larger than the track pitch and securing a write magnetic field strong enough to reverse the magnetization of the magnetic layer, and further by writing while shifting a write head comprising the write element, a magnetic disk drive, of which the track width is narrower than the write element width, and the storage capacity is large, is realized.

Magnetic disk drive

In one embodiment, a symbol error correction encoder effects block interleaving on recording data and thereafter performs first error correction encoding on the recording data. Next, a symbol error correction encoder performs encoding on the whole block. A reproducing processing circuit outputs likelihood information of respective bits. A first error correction decoder corrects a random error produced upon recording and reproduction, using the likelihood information. Since it is possible to make an improvement in performance with respect to the random error by repetitive decoding at this time, the post-correction data is returned to the reproducing processing circuit. After the completion of such repetitive processing, the data is digitized and subjected to an error correction in symbol unit by a hard determination, and outputted to a symbol error correction decoder.

Signal processing method and signal processing circuit

A magnetic recording/reproducing apparatus includes a partial-response equalization circuit having frequency characteristic of cutting off low-frequency signal components inclusive of DC components; and a maximum-likelihood decoder, in which a reproduced signal outputted from the reproducing head is processed by the partial-response equalization circuit and then inputted into the maximum-likelihood decoder to be data-reproduced, thereby reducing a noise and distortion on the reproduced signal and reducing a data detection error rate.

Device and signal processing circuit for magnetic recording, magnetic recording apparatus

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Kokubunji, Japan

Hideki Sawaguchi