Patents Examined by Dan I Davidson
  • Patent number: 7315427
    Abstract: A dynamic threshold detector for a magnetic storage medium comprises a transition detector that receives the data comprising pairs of numbers based on data received from the magnetic storage medium, each of the pairs of numbers including a first number and a second number and that detects signs of the first and second numbers in the pairs. A threshold selector varies a magnitude of a threshold based on the detected signs.
    Type: Grant
    Filed: July 25, 2006
    Date of Patent: January 1, 2008
    Assignee: Marvell International Ltd.
    Inventor: Zining Wu
  • Patent number: 7304816
    Abstract: In a method for predicting failure of a disc drive during operation of the disc drive, a write fault count is maintained that corresponds to write faults encountered during write operations to a disc of the disc drive. Additionally, a frequency domain representation of a position error signal of a head of the disc drive is obtained. Finally, failure of the disc drive is predicted based on the write fault count and the frequency domain representation of the position error signal. Another aspect of the present invention relates to a disc drive that is capable of performing the above-described method.
    Type: Grant
    Filed: June 15, 2005
    Date of Patent: December 4, 2007
    Assignee: Seagate Technology LLC
    Inventors: Cary Dean Johnson, Gary Gang Jing, Matthew Edward Hastings, Todd Phillip Fracek, Paul William Burnett, Feng Li, Wei-Hua Lin
  • Patent number: 7295394
    Abstract: Provided are a method and apparatus for equalizing and demodulating an information signal recorded in a magnetic recording medium by a partial response signal processing system if an isolated reversion producing waveform reproduced from the magnetic recording medium indicates an asymmetry. The method and apparatus reproduce the information signal from a high recording density of the magnetic recording medium.
    Type: Grant
    Filed: June 7, 2005
    Date of Patent: November 13, 2007
    Assignee: Fujifilm Corporation
    Inventors: Takeshi Nagata, Naoto Abe, Hisashi Osawa, Yoshihiro Okamoto
  • Patent number: 7289284
    Abstract: Embodiments of the invention prevent demagnetization or degaussing of recorded magnetizations, even if a stray field is applied. In one embodiment, an output of a read head including a magneto-resistive effect element is inputted to a stray field detector through a DC amplifier and a DC filter. The stray field detector monitors dc components of the output from the read head, and escapes a head from above a magnetic recording medium.
    Type: Grant
    Filed: August 1, 2005
    Date of Patent: October 30, 2007
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Reiko Arai, Takehiko Hamaguchi, Atsushi Kikugawa, Hideaki Maeda, Liping Shen, Mikio Suzuki
  • Patent number: 7286312
    Abstract: An apparatus, method, and system for providing dc offset reduction in a communications channel include two or more feedback loops to generate dc offset correction signals, which in turn are combined with an input analog signal and a processed digital signal thereby reducing dc offset. Each feedback loop may include an adaptive filter. At least one feedback loop may be responsive to an error signal that represents the difference between the delayed input of a first detector, and its output. Further, the dc offset correction signal, partially delayed, may be added to the error signal, thereby improving the response time of the dc offset correction loop.
    Type: Grant
    Filed: August 8, 2006
    Date of Patent: October 23, 2007
    Assignee: Marvell International Ltd.
    Inventor: Mats Oberg
  • Patent number: 7277245
    Abstract: A write driver circuit for a magnetic storage medium that communicates with a write head having first and second nodes comprises a first driver circuit with an input and an output that communicates with the first node of the write head. A first charge pump communicates with said input and said output of said first driver circuit and provides additional current to said input of said first driver circuit during a first transition period between current flowing through the write head in a first direction and current flowing through the write head in a second direction. A second driver circuit with an input and an output communicates with the second node of the write head. A second charge pump communicates with said input and said output of said second driver circuit and provides additional current to said input of said second driver circuit during a second transition period between current flowing through the write head in said second direction and current flowing through the write head in said first direction.
    Type: Grant
    Filed: March 28, 2005
    Date of Patent: October 2, 2007
    Assignee: Marvell International Ltd.
    Inventors: Farbod Aram, Sehat Sutardja
  • Patent number: 7274524
    Abstract: A signal detector to detect symbols in a read back signal. The signal detector includes a first detector to generate raw decisions as a function of the read back signal. A post processor identifies possible defects in the raw decisions. A selector selects a portion of the possible defects and generates modified decisions based upon correcting the portion of the possible defects. At least one signal decoder generates final decisions as a function of the modified and raw decisions. A decision block returns control to the selector in response to detecting excess errors in the final decisions.
    Type: Grant
    Filed: March 28, 2005
    Date of Patent: September 25, 2007
    Assignee: Marvell International Ltd.
    Inventors: Gregory Burd, Zining Wu, Mats Oberg, Pantas Sutardja
  • Patent number: 7271970
    Abstract: A conventional magnetic head has a structure, in which a MR element and a recording element are stacked. The influence of a recording magnetic field on the magnetically sensitive portion of a reproduction element is lessened and the performance of the MR element is stabilized. Also, the reliability of the magnetic disk drive using a MR element is enhanced. The magnetic disk drive uses a composite magnet head, which has a plurality of reproduction elements arranged such that the magnetically sensitive layer of a reproduction element of the composite magnetic head does not overlap with the normal direction projection of the recording element, and which lessens the influence of a recording magnetic field on the magnetically sensitive portion of each reproduction element.
    Type: Grant
    Filed: October 15, 2004
    Date of Patent: September 18, 2007
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventor: Reijiro Tsuchiya
  • Patent number: 7268962
    Abstract: A disk drive including a self-servo writing apparatus is disclosed. The self-servo writing apparatus calculates a pitch of servo tracks constituted on a disk medium by a calculation method using a positional error calculation value based on a reproduction amplitude value of a servo burst pattern signal reproduced by a head.
    Type: Grant
    Filed: September 22, 2004
    Date of Patent: September 11, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Hideo Sado
  • Patent number: 7265923
    Abstract: An HDC has first and second terminals. The first terminal is used to output a first write gate signal that dictates writing of data to the disk. The second terminal is used to input a second write gate signal output from an external circuit. The external circuit performs predetermined signal processing on write data in accordance with the first write gate signal output from the first terminal, and outputs the second write gate signal that reflects a signal delay in the circuit. A write inhibition controller incorporated in the HDC monitors the second write gate signal input via the second terminal, and detects, as a write inhibition state, a state in which writing of data to the disk is dictated during a period in which writing of data to the disk should be inhibited.
    Type: Grant
    Filed: January 30, 2004
    Date of Patent: September 4, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Fubito Igari
  • Patent number: 7262928
    Abstract: An apparatus, method, and system for providing dc offset reduction in a communications channel include a feedback loop to generate dc offset correction signals, which in turn are combined with an input analog signal and a processed digital signal thereby reducing dc offset. Each feedback loop may include an adaptive filter. At least one feedback loop may be responsive to an error signal that represents the difference between the delayed input of a first detector, and its output. Further, the dc offset correction signal, partially delayed, may be added to the error signal, thereby improving the response time of the dc offset correction loop.
    Type: Grant
    Filed: August 8, 2006
    Date of Patent: August 28, 2007
    Assignee: Marvell International Ltd.
    Inventor: Mats Oberg
  • Patent number: 7259929
    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.
    Type: Grant
    Filed: June 24, 2005
    Date of Patent: August 21, 2007
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Hideki Sawaguchi, Yasutaka Nishida, Hisashi Takano, Toru Matsushita
  • Patent number: 7253982
    Abstract: Dynamically detecting off-track errors in a disk drive by adjusting transducer head position control parameters in response to shock events. In an embodiment, shock events with large magnitude trigger a severe shock timer which lengthens the write fault before write operations resume. In another embodiment, a lower shock threshold is used following an initial shock event. In yet another embodiment, a lower shock threshold is used if an accumulated average position error of the transducer head is large.
    Type: Grant
    Filed: April 19, 2005
    Date of Patent: August 7, 2007
    Assignee: Maxtor Corporation
    Inventors: Don Brunnett, John Purkett, Bruce Liikanen
  • Patent number: 7253980
    Abstract: Circuitry for detecting and recording latches in read bias current may include circuitry for generating a reference voltage, a pair of current to voltage converters to convert the bias and reference currents to voltage signals, a comparator to compare those two voltages, a latch to latch the compared signal, and a counter/register to count and store the number of glitches that have been detected. It may be possible to read from the register the number of detected glitches to be used in diagnosing faults in the disk drive system. In addition, it may be possible to provide a reset input to the register to zero the counter.
    Type: Grant
    Filed: June 3, 2005
    Date of Patent: August 7, 2007
    Assignee: Maxtor Corporation
    Inventors: Bac Pham, Xiaokun Chew
  • Patent number: 7251095
    Abstract: The present invention is directed to a method and apparatus for performing best head detection in a disk drive using reference tracks. In one embodiment, a disk drive includes a plurality of disk surfaces. Each disk surface has a read head and a write head associated therewith. A servo track writer is provided for moving each write head and each read head relative to their corresponding disk surfaces. Reference tracks are written onto each of the disk surfaces. The reference track from each disk surface is read by its corresponding read head to determine a best read head. In one embodiment, the servo track writer sweeps each read head across its corresponding reference track as the reference track is being read. In one embodiment, each reference track includes reference track patterns and the best read head is the read head that detects the most patterns.
    Type: Grant
    Filed: June 2, 2004
    Date of Patent: July 31, 2007
    Assignee: Maxtor Corporation
    Inventors: Brian Rigney, Jason Laks, Todd Franks
  • Patent number: 7239467
    Abstract: The storage media recording/writing system includes a media drive circuit, a head retaining means, a head moving means, a head drive circuit, a signal processing circuit, and a controller to control these. The head drive circuit possesses a first semiconductor integrated circuit having an amplifier that amplifies the read signal from the head, and a second semiconductor integrated circuit placed between the first semiconductor integrated circuit and the signal processing circuit, which has a circuit that receives write data from the signal processing circuit and generates a drive signal to drive a write head. Further, the first semiconductor integrated circuit is mounted on a part near the front of the head retaining means, and the second semiconductor integrated circuit is installed on the side of the moving means.
    Type: Grant
    Filed: April 29, 2004
    Date of Patent: July 3, 2007
    Assignee: Hitachi, Ltd.
    Inventors: Hiroyasu Yoshizawa, Yoichiro Kobayashi, Toshio Shinomiya, Noriyuki Fujii, Masaki Yoshinaga
  • Patent number: 7233452
    Abstract: Disclosed is a preamplifier circuit of a magnetic record regeneration apparatus with a write system and a read system, certainly verifying a write function in a short period of time. The preamplifier circuit includes, in the write system, a write driver; a current-voltage conversion circuit for converting the write current from the write driver into a corresponding voltage; a waveform shaping circuit for converting the output voltage from the current-voltage conversion circuit into a full-wave rectified waveform; a peak-hold circuit for holding a peak value of the output from the waveform shaping circuit; a filter circuit for outputting an average voltage of the output from the waveform shaping circuit; and a determination circuit for determining that the write driver is abnormal based on each output status of the peak-hold circuit and the filter circuit.
    Type: Grant
    Filed: July 22, 2005
    Date of Patent: June 19, 2007
    Assignee: Fujitsu Limited
    Inventor: Masao Kondou
  • Patent number: 7227711
    Abstract: A hard disk drive (HDD) detects and measures external stray magnetic fields with existing HDD components. After detecting a strong external magnetic field, read and write operations of the HDD are suspended, and/or other proper corrective actions are taken to minimize loss of data. To measure the stray magnetic field, the magnetic head reader is used as a field sensor. The resistance of the reader changes in the presence of the field, such as with the preamp in the HDD. The resistance also changes with temperature. If the temperature inside the HDD is measured, the resistance change due to temperature is normalized. Even without being able to measure the HDD temperature, the stray magnetic field can be measured with a top head and a bottom head in the HDD. The temperature sensitivity of the reader is thereby cancelled out.
    Type: Grant
    Filed: October 29, 2004
    Date of Patent: June 5, 2007
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Xiaodong Che, Wen-Chien David Hsiao, Yansheng Luo, Xiaoyu Sui
  • Patent number: 7218468
    Abstract: Synchronized data is written to magnetic tape while reducing the number of backhitches. A controller detects a pattern of synchronizing events for received data records to be written to tape; writes each transaction of data records to the magnetic; tape; accumulates the synchronized transactions in a buffer; and subsequently recursively writes the accumulated transactions of data records from the buffer to the magnetic tape in a sequence. A single backhitch may be employed to place the recursively written accumulated data records following the preceding data, maximizing performance and capacity.
    Type: Grant
    Filed: January 25, 2005
    Date of Patent: May 15, 2007
    Assignee: International Business Machines Corporation
    Inventors: Glen Alan Jauette, Paul Merrill Greco, James Mitchell Karp
  • Patent number: 7218465
    Abstract: A stamper/imprinter for use in forming a magnetic transition pattern in a magnetic material by means of contact printing, comprising: (a) a non-magnetic substrate having a major surface comprising a patterned plurality of spaced-apart recesses with a plurality of non-recessed areas therebetween, the patterned plurality of recesses corresponding to the magnetic transition pattern to be formed in the magnetic material; and (b) unidirectionally permanently magnetized material filling each of the plurality of recesses and having exposed surfaces substantially coplanar with the plurality of non-recessed areas.
    Type: Grant
    Filed: June 4, 2003
    Date of Patent: May 15, 2007
    Assignee: Seagate Technology LLC
    Inventors: Neil Deeman, Shih-Fu Lee