Patents Examined by Alan Faber
  • Patent number: 7012772
    Abstract: A sampled amplitude read channel is disclosed for magnetic disk storage systems comprising an adaptive non-linear correction circuit for correcting non-linear distortions in the read signal, such as asymmetry caused by the non-linear response of a magneto-resistive (MR) read head. The analog read signal is sampled and the discrete time sample values equalized into a desired partial response prior to sequence detection. The non-linear correction circuit is inserted into the read path prior to the sequence detector and adaptively tuned by a least-mean-square (LMS) adaptation circuit. In one embodiment, the non-linear correction circuit is a discrete-time Volterra filter comprising a linear response for implementing an equalizing filter, and a non-linear response for attenuating non-linear distortions in the read signal. The filter coefficients of both the linear and non-linear sections of the Volterra filter are adaptively adjusted by the LMS adaptation circuit.
    Type: Grant
    Filed: September 2, 1998
    Date of Patent: March 14, 2006
    Assignee: Cirrus Logic, Inc.
    Inventor: Marvin L. Vis
  • Patent number: 6765739
    Abstract: A method and apparatus for creating a machine-readable medium such as a CD or a DVD disc is disclosed. The disc includes encoded copy protection data that, when decoded and re-encoded, produces a tracking prevention sequence of bits that causes a duplicate disc (containing the re-encoded copy protection data) to temporarily lose tracking. The temporary loss of tracking is utilized to render the duplicated disc unusable by placing key data immediately following the encoded copy protection data.
    Type: Grant
    Filed: March 18, 2002
    Date of Patent: July 20, 2004
    Assignee: Hewlett-Packard Development Company, L.P.
    Inventors: Josh N. Hogan, David K. Towner
  • Patent number: 6757118
    Abstract: A programmable controller and method for correcting operation of a read/write head in a disc drive having an embedded servo system in which the head is not reading correctly operates by applying a write current to the failed head only after the head is positioned over an area of a disc that does not have useful data thereon. Movement and position of the head that is not reading correctly is determined from a signal from an adjacent head. The adjacent head is used to read servo information. After the adjacent head has provided servo information and the controller repositions the adjacent head in a safe area, a write current is applied to the failed head to realign the head without the potential of adversely impacting data stored in adjacent tracks.
    Type: Grant
    Filed: January 20, 2000
    Date of Patent: June 29, 2004
    Assignee: Seagate Technology LLC
    Inventors: Timothy Ted Walker, Matthew Chad Burton
  • Patent number: 6757121
    Abstract: An extra-HDA record reproducing circuit for outputting write data comprising parallel data is provided outside a disk assembly, and a intra-HDA record reproducing circuit comprising a parallel-to-serial conversion circuit for receiving write data comprising parallel data and converting the write data to serial data, a write amplifier for switching a polarity of a recording current to be supplied to a head according to the write data converted to serial data, and a preamplifier for amplifying a read signal detected by the head is provided within the disk assembly, and the write data is transferred at a high speed at least from the extra-HDA record reproducing circuit to the intra-HDA record reproducing circuit.
    Type: Grant
    Filed: August 28, 2001
    Date of Patent: June 29, 2004
    Assignee: Fujitsu Limited
    Inventor: Hiroshi Uno
  • Patent number: 6690524
    Abstract: An apparatus and method are disclosed for improving data recovery operations in a disc drive employing a redundant sync data block format. The disc drive includes a rotatable disc and a controllably positionable head which is used to store user data in a plurality of data blocks on tracks of the disc. Each data block includes a user data field to store user data, a first sync field and a redundant, second sync field, the sync fields storing first and second sync words, respectively, which establish symbol boundaries used by a read channel of the disc drive. User data are recovered from a selected data block by initiating a delay of selected duration during which a first portion of the selected data block passes proximate the head, allowing the second, remaining portion of the selected data block to be read at the completion of the delay.
    Type: Grant
    Filed: July 20, 2000
    Date of Patent: February 10, 2004
    Assignee: Seagate Technology LLC
    Inventors: Shawn Alan Wakefield, Jimmie Ray Shaver, Brett Alan Sloan
  • Patent number: 6665135
    Abstract: A disk drive system including a write circuit for controlling current through a magnetic write head includes an H-switch circuit and a pulse-mode power supply circuit. The H-switch circuit controls direction of current through the magnetic write head. The pulse-mode power supply circuit is connected to the H-switch circuit for providing a higher voltage pulse at a beginning of a switching event of the H-switch circuit to accelerate a change in direction of current through the write head, followed by a lower voltage until a next switching event.
    Type: Grant
    Filed: June 8, 2001
    Date of Patent: December 16, 2003
    Assignee: Agere Systems Inc.
    Inventors: Jong K. Kim, Elanguvan Nainar
  • Patent number: 6545833
    Abstract: A disc drive typically contains at least one disc which is divided into sectors. The method of eliminating reassignments involves copying data stored at one sector (referred to as a moving sector) to another sector (referred to as a moving spare), and assigning the logical address associated with the moving sector to the moving spare. The elimination process is repeated until the reassignments are eliminated. Verification of the data copied is conducted to ensure data integrity. Furthermore, the elimination process is preferably executed only when the disc drive is in an idle mode. Records are kept and updated as the process is carried out so that the process can be continued even if interrupted.
    Type: Grant
    Filed: April 28, 2000
    Date of Patent: April 8, 2003
    Assignee: Seagate Technology LLC
    Inventors: Chwee Fern Ee, Yong Peng Chng, Chew Boon Toh, Wing Hung Chan
  • Patent number: 6307694
    Abstract: The invention includes disk drive circuitry, systems, and methods. The disk drive system comprises control circuitry and a disk device. The disk device stores data and transfers an analog signal representing the data. The control circuitry receives the analog signal, converts the analog signal into a digital signal, transfers the digital signal, and biases an error signal. The control circuitry includes an analog-to-digital converter, adaptive filter, a decoder, and error signal circuitry. The analog-to-digital converter receives and samples the analog signal to generate a sampled signal. The adaptive filter shapes the sampled signal based on coefficients to produce a shaped signal. The decoder decodes the shaped signal to generate the digital signal. The error signal circuitry generates the biased error signal to adjust the coefficients in the adaptive filter.
    Type: Grant
    Filed: February 24, 1999
    Date of Patent: October 23, 2001
    Assignee: Cirrus Logic, Inc.
    Inventors: Li Du, Mark Stephen Spurbeck, Richard Travis Behrens
  • Patent number: 6215607
    Abstract: A write driver circuit for selectively controlling a direction of write current flow through a magnetic head having an inductive coil includes a source of first and second write currents. A forward drive switch directly sinks the first write current and sinks the second write current through the coil in a first direction. A reverse drive switch directly sinks the second write current and sinks the first write current through the coil in a second direction opposite the first direction. A control circuit operates the forward and reverse drive switches so that write current flows through the coil in a selected direction. An overshoot reduction circuit may be provided to reduce write current overshoot through the coil. An active subcircuit generates a compensation signal based on a voltage across the head exceeding a predetermined threshold. The first and second write currents are adjusted in response to the active subcircuit based on the compensation signal.
    Type: Grant
    Filed: June 2, 1997
    Date of Patent: April 10, 2001
    Assignee: Lucent Technologies Inc.
    Inventor: Tuan V. Ngo
  • Patent number: 6166871
    Abstract: A method for generating a reliable head position signal including track number validation. A head position signal is generated using two triangular signals PosN and PosQ having a phase difference of a 1/4 period, and a track number which is recorded on the medium. The track number is validated by comparing the relationship of the signs of the signals PosN, PosQ with the track number according to a predetermined rule. The track number may be a corrected if the track number was misread. Subsequently, a position signal generator demodulates the position signal on the basis of the absolute values of signals PosN, PosQ, the signs of the signals PosN, PosQ, and the track number. The accuracy of the head position signal is further improved using a conversion coefficient (position sensitivity factor) for correcting the amplitudes of the signals PosN and PosQ.
    Type: Grant
    Filed: July 28, 1997
    Date of Patent: December 26, 2000
    Assignee: Fujitsu Limited
    Inventor: Kazuhiko Takaishi
  • Patent number: 6137646
    Abstract: A disk apparatus has a disk medium with sector areas that have a servo area and a data area along the same cylinder. The servo areas also have a sector mark indicative of the servo area, a code indicative of a cylinder address, and a predetermined servo pattern to detect a head position, all magnetically recorded in the servo area. A disk control section uses a head portion to detect the head position on the basis of a read signal of the servo pattern and positions the head portion at an arbitrary cylinder to perform reading and writing operations. The disk apparatus also has a time measuring counter for starting to measure an elapsed time each time a predetermined position in the servo area is detected, and a time setting register for storing a time from a detection time point of the predetermined position in the servo area to the generation of the sector pulse.
    Type: Grant
    Filed: June 10, 1997
    Date of Patent: October 24, 2000
    Assignee: Fujitsu Limited
    Inventors: Eiji Okamura, Tatsuya Gofuku, Chihiro Ono, Kazuhide Ohba, Atsushi Satoh, Eisaku Takahashi, Takashi Tokairin, Isao Suda
  • Patent number: 6130793
    Abstract: A thermal asperity detection method includes the steps of (a) converting an analog signal reproduced from a magnetic recording medium into a digital signal using an analog-to-digital converter, (b) detecting thermal asperity based on the digital signal, and (c) automatically recognizing and managing detection of the thermal asperity by the step (b) by firmware.
    Type: Grant
    Filed: March 21, 1997
    Date of Patent: October 10, 2000
    Assignee: Fujitsu Limited
    Inventors: Hideki Ohmori, Masahide Kanegae, Isamu Tomita
  • Patent number: 6124995
    Abstract: In a fixed bit-rate encoding method, a unit block composed of a predetermined number of transform blocks is constructed by dividing input image data into transform blocks and a unit for fixing the bit-amount is constructed by extracting one of the predetermined number of unit blocks, to thereby perform transform-encoding. A real compression scale factor is calculated by quantizing the transform coefficient obtained by a transform-encoding operation according to initial compression scale factors and by comparing the bit-amount quantized in a unit block with a target bit-amount. The transform coefficient is quantized in a unit block using said real compression scale factor, and the quantized transform coefficient is variable-length-encoded to have the bit-amount fixed in an bit-amount fixing unit. The encoded DC coefficient and a predetermined number of low-frequency AC coefficients are recorded in an IDC data region and the all of the encoded coefficients are recorded in a DDC data region.
    Type: Grant
    Filed: November 17, 1997
    Date of Patent: September 26, 2000
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Jae-hyun Kim
  • Patent number: 6104560
    Abstract: In a data reproducing device using a read channel of a PRML system, during a period of a continuous reproducing operation mode for continuous reproduction processing of adjacent data sectors, a restart RG generator switches a restart read gate signal RRG ON in synchronization with switching ON of a reference read gate signal RG. Therefore, when data is reproduced from a data sector before continuous data sectors, data reproduction processing is started by means of the restart read gate signal RRG equivalent to the reference read gate signal RG. When data is continuously reproduced from a next data sector adjacent to the previous data sector, the restart RG generator switches the restart read gate signal RRG ON ahead of the reference read gate signal RG by a specified period.
    Type: Grant
    Filed: September 29, 1998
    Date of Patent: August 15, 2000
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Masahiko Tsunoda
  • Patent number: 6101060
    Abstract: A method and associated apparatus for reduction of data loss errors in computer data tape transport applications. In tape transport devices with moveable read heads (i.e. auto-tracking read/playback heads), by sensing telemetry information regarding tape movement and alignment of a position on the tape medium before the position on the tape encounters the moveable head. Prior systems provided for such sensing only as the tape was read by the moveable head such that compensation could be made only for subsequent read operation. By sensing the telemetry data in advance of the tape encountering the moveable head, the head may be adjusted in time to encounter the misaligned tape medium compensating for the misalignment. Similarly, telemetry data relating to the speed of the tape motion as sensed by a channel reading a predetermined recorded sequence of bits permits compensation for both erroneous tape speed and tape medium stretch or contraction.
    Type: Grant
    Filed: May 28, 1999
    Date of Patent: August 8, 2000
    Assignee: Storage Technology Corporation
    Inventors: Matthew Peter Wojciechowski, Joe Kent Jurneke
  • Patent number: 6078454
    Abstract: When a combination head is on-tracked to an arbitrary cylinder position, a head position controller corrects a head position so as to eliminate an offset amount derived from an offset table. A bias current setting circuit obtains a current set value corresponding to an offset correction amount from a bias current table and supplies the bias current according to the current set value to an MR head. As kinds of offsets, there are a yaw angle offset, a thermal offset, and a core deviation offset.
    Type: Grant
    Filed: December 15, 1995
    Date of Patent: June 20, 2000
    Assignee: Fujitsu Limited
    Inventors: Tsuyoshi Takahashi, Toshihiko Matsuda, Takehiko Tsuboi, Koji Ikenoya, Yukio Abe, Koji Ishii, Tomoo Furukawa, Hiroyuki Kobayashi
  • Patent number: 6072650
    Abstract: The invention comprises a magnetic disk storage system and comprises method for configuring the magnetic disk storage system. The magnetic disk storage system facilitates write and read operations that compensate for variances that are experienced with magnetic disk storage systems. When writing data to a data sector, the magnetic disk storage system utilizes a phase lock oscillator field that has a length that is specified for that data sector. When reading from a data sector, the magnetic disk storage system utilizes an incremental read delay that has a duration that is specified for that data sector. Data sectors with shorter data sector delay periods can have shorter phase lock oscillator fields than data sectors with larger data sector delay periods. This frees-up memory space and increases the capacity and performance of the magnetic disk storage system.
    Type: Grant
    Filed: September 29, 1997
    Date of Patent: June 6, 2000
    Assignee: STMicroelectronics N.V.
    Inventor: Aaron Wade Wilson
  • Patent number: 6072644
    Abstract: A process and device are disclosed for reading weak magnetically recorded signals from a photographic film provided with a transparent thin magnetic layer. The signals from a magnetic read head obtained from the moving film are pre-amplified and the pre-amplified signals are digitized, filtered, differentiated and evaluated. The output of the magnetic read head (2) is supplied to the pre-amplifier (5) in short-circuit. This means that the internal resistance R.sub.i of the magnetic head is very high compared to the input resistance R.sub.e of the amplifier connected immediately downstream of the magnetic read head coil.
    Type: Grant
    Filed: September 10, 1997
    Date of Patent: June 6, 2000
    Assignee: Agfa-Gevaert Aktiengesellschaft
    Inventor: Volker Weinert
  • Patent number: 6069758
    Abstract: A hard disk drive with a reduced read channel optimization test time and a reduced test time difference determines whether or not the time limit for testing the hard disk drive has elapsed whenever the test by the zones and heads is completed, so that the test time difference between the respective drives may be prevented. Further, the test progresses from the last zone to the first zone. Thus, although the test is halted in the course of performing the test, the zone with the high error rate can be tested. In addition, a determination is made as to whether or not the error rate is high or not at the steps of selecting the test track and determining the test off-track. If it is determined that the error rate is high, the total number of sectors to be read for the test will be adjusted, thereby reducing the test time delay due to the high error rate.
    Type: Grant
    Filed: December 31, 1997
    Date of Patent: May 30, 2000
    Assignee: SamSung Electronics Co., Ltd.
    Inventor: Young-Seok Chung
  • Patent number: 6067205
    Abstract: A head positioning system accurately positions a read/write head along a selected track of a rotating magnetic disk. In one aspect, servo information is embedded along the track with the centerline of the servo information offset a radial distance from the centerline of data stored or written along the track. The head positioning system micro-jogs the read/write head a first and a second radial distance from the centerline of servo information for a read operation and a write operation.
    Type: Grant
    Filed: March 23, 1999
    Date of Patent: May 23, 2000
    Assignee: Maxtor Corporation
    Inventors: Harlan Mathews, James A. Valent