Abstract: 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.

Abstract: The object of the invention is to provide an efficient encoding method for error correction coding for recording/reproducing information in high-density magnetic recording/reproduction apparatus. Based upon the principle of Turbo coding for powerful random error¥correction, this invention provides a practical encoding method 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. In addition, the object is to reduce decoding time delay (latency) in iterative decoding for the error-correction and realize high-speed operation for error correction. To achieve the objects, 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 applied.

Abstract: 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.

Abstract: The present invention discloses an information processing method including the following steps:

Abstract: 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.

Abstract: A maximum likelihood decoding circuit is arranged to reduce the power consumption through the effect of the Viterbi algorithm. A plurality of storing elements 61a to 61h located vertically in a column and for storing each state survivor path information at the same time point are treated as storing element blocks 60(1) to 60(D) in a manner to correspond to the combination (state) of intra-code interferences. The outputs from the storing elements 61a to 61h are again applied into the inputs of the corresponding storing elements contained in the same storing element block through the path history selecting circuits 62a to 62h. Each of the storing element block 60(1) to 60(D) is periodically started on the input timing of a receiving signal at each processing time point by starting points (pointers) 63(1) to 63(D) outputted from a starting signal (pointer) generating circuit 68.

Abstract: In a thermal assisted type magnetic disk apparatus having a head holding a heat element and a write element, in which coercivity of a disk is locally reduced by temperature-increasing the disk and writing is performed by the write element, along with a seek operation to move the head by a rotary actuator in a radial direction, a yaw angle is changed and a heat area and the write element are track-shifted. A mechanism to offset one of the heat area and the write element in a width direction of a slider, to array the heat element and the write element in a track running direction in correspondence with the yaw angle of the head.

Abstract: The present invention discloses an information processing method including the following steps: (1) a first step receiving an encoded information data series as input; (2) a second step selecting a candidate decoded data code series from a first candidate decoded data code series group, decoding the encoded information data series, and generating a first decoded data code series; (3) a third step detecting a position and contents of erroneous decoded data codes in the first decoded data code series that cannot exist in the information data code; (4) a fourth step correcting the erroneous decoded data code and generating a corrected data code; (5) a fifth step selecting a single decoded data code series out of a second candidate decoded data code series group, decoding the encoded information data code series again, and generating a second decoded data code series; (6) The second candidate decode data code series group includes candidate decoded data code series from the first candidate decoded data code

Abstract: A method of enhancing the thermal stability of gray codes is disclosed. The gray code block in a servo area is recorded with a combination of two different magnetization directions. When the two different magnetization directions are expressed as “+” and “−”, the information “1” is recorded as “++−−” or “−−++” with the information “0” recorded as “+−+−” or “−+−+”. Since the filter for gray code demodulation is provided with a perpendicular recording mode, the servo area does not use long-wavelength signals that are susceptible to thermal demagnetization. As a result, thermal stability is enhanced.

Abstract: When the amount of position error PE of a magnetic head meets the condition of Ewf>PE>=Eww for two threshold values Ewf and Eww meeting Ewf>Eww, the track is registered in the track information table as a track requiring rewrite and the tracks on both sides neighboring to the track are temporarily write-inhibited. The data of the track is rewritten on another track later so as to maintain the data. By doing this, the offtrack of the recording track can be made smaller without sacrifice of the access speed and the occurrence probability of write fault can be reduced. Furthermore, the reliability of a magnetic disk apparatus can be improved.

Abstract: For the purpose of letting through a magnetic flux which reverses the magnetization of the magnetic layer of the magnetic disk, a write element requires a predetermined sectional area. However, if a cross section of a magnetic pole is structured as the one having a large aspect ratio, the pole becomes less capable of letting the magnetic flux through effectively. This phenomenon brings about a lower limit on the track width of the magnetic poles and the track density cannot be raised. 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.

Abstract: In the PRML signal processing technique, reduction of data detection error events caused due to medium noise that occurs depending on a recording code data pattern is realized by using simple means. With respect to a detection data result obtained after PRML data demodulation, a code error event that depends on a signal distance and has a high frequency of occurrence is noticed and its occurrence probability is estimated. At this time, a locally existing medium noise quantity is estimated from preceding and subsequent code patterns of the PRML detection data result. Thereby the occurrence probability of the error event is compensated to improve the detection precision. As a result, data modulation with reliability higher than conventional maximum likelihood detection can be realized with a simple circuit structure.

Abstract: In a data demodulating method, predetermined input data is demodulated based upon a response characteristic of the partial response class 4; the demodulated input data is discrete-filtered to thereby produce filtering data; and the filtering data is maximum likelihood-decoded to thereby producing asymmetrical response data. Further, a magnetic recording/reproducing apparatus is arranged by using this data demodulating method.

Abstract: 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.

Abstract: 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.

Abstract: A maximum likelihood decoding circuit is arranged to reduce the power consumption through the effect of the Viterbi algorithm. A plurality of storing elements 61a to 61h located vertically in a column and for storing each state survivor path information at the same time point are treated as storing element blocks 60(1) to 60(D) in a manner to correspond to the combination (state) of intra-code interferences. The outputs from the storing elements 61a to 61h are again applied into the inputs of the corresponding storing elements contained in the same storing element block through the path history selecting circuits 62a to 62h. Each of the storing element block 60(1) to 60(D) is periodically started on the input timing of a receiving signal at each processing time point by starting points (pointers) 63(1) to 63(D) outputted from a starting signal (pointer) generating circuit 68.

Abstract: When the amount of position error PE of a magnetic head meets the condition of Ewf>PE>=Eww for two threshold values Ewf and Eww meeting Ewf>Eww, the track is registered in the track information table as a track requiring rewrite and the tracks on both sides neighboring to the track are temporarily write-inhibited. The data of the track is rewritten on another track later so as to maintain the data.

Abstract: 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.

Abstract: A magnetic storage apparatus is provided with unit for identifying the frequency of overwriting storage at the time of overwriting in the same data sector, and depending on the frequency of overwriting, a code for coding or a scrambler initial value is changed at every overwrite operation. The modulation code has the same code rate so that a data length does not change at every write operation. A number corresponding to the present modulation code of each data sector is stored on a memory, and the aforesaid number is also written as an additional bit in the data sector on a medium. Data are read only when the modulation coding number on the memory and the modulation coding number on the medium, which are compared, agree with each other. If they do not agree, offset reading is performed until they agree, and then the read operation is performed.

Abstract: In a data demodulating method, predetermined input data is based upon a response characteristic of the partial response class 4. The predetermined input data is discrete-filtered to thereby produce filtered asymmetrical data. The filtered asymmetrical data is maximum-likelihood-decoded to thereby produce decoded data that is demodulated. Further, a magnetic recording/reproducing apparatus is arranged by using this data demodulating method.