Patents Examined by Regina Y. Neal
  • Patent number: 7126775
    Abstract: A rate ½, d=1 channel code encodes a Gray code servo track address into channel data recorded on a magnetic disk; a d=1 Viterbi sequence detector detects the recorded servo track address upon read back; a cost effective d=1 decoder decodes the recorded servo track address into its Gray code representation; and a 1/1+D filter decodes the Gray code track address into its binary representation. The channel encoding scheme increases the data density of the storage system due to the d=1 constraint and use of the Viterbi sequence detector. Further, the implementation advantageously uses the Viterbi sequence detector already provided in a read channel for detecting user data, and the cost and complexity of the decoder is reduced by encoding/decoding the Gray code track address in sections of five bits.
    Type: Grant
    Filed: July 10, 1996
    Date of Patent: October 24, 2006
    Assignee: Cirrus Logic, Inc.
    Inventor: Christopher P. Zook
  • Patent number: 6611397
    Abstract: Apparatus and method for improving operational performance of a disc drive by detecting defective servo burst patterns. A rotatable disc is provided with servo data which include a plurality of servo burst patterns to define a plurality of tracks. A head transduces the burst patterns to provide burst signals to a servo circuit which controllably positions the head with respect to the surface of the disc by determining a position error signal from a combination of the burst signals. The servo circuit identifies a selected servo burst pattern as defective in relation to differences between absolute values of successive pairs of peak amplitude samples from the burst signal.
    Type: Grant
    Filed: June 4, 1999
    Date of Patent: August 26, 2003
    Assignee: Seagate Technology LLC
    Inventor: Hieu V. Nguyen
  • Patent number: 6606212
    Abstract: A magnetic recording channel front-end for a magnetic storage system includes a magnetoresistive element, an interconnect and a readback amplifier. The interconnect, which has a characteristic impedance, couples the magnetoresistive element to the readback amplifier. The readback amplifier includes a gain stage and an active termination. The gain stage, which has an associated impedance, has an input that is connected to the interconnect. The active termination is coupled to the input of the gain stage, such that an input impedance of the readback amplifier, which is formed by a combination of the impedance associated with the gain stage and the active termination, is substantially equal to the characteristic impedance of the interconnect. Additionally, the gain stage generates a first noise signal that has a first magnitude appearing at an output of the gain stage. The active termination generates a second noise signal that has a second magnitude that also appears at the output of the gain stage.
    Type: Grant
    Filed: March 17, 1999
    Date of Patent: August 12, 2003
    Assignee: International Business Machines Corporation
    Inventors: Klaassen Berend Klaassen, Jacobus Cornelis Leonardus Van Peppen
  • Patent number: 6473254
    Abstract: A plurality of patterns are formed so that each is deviated slightly from another in each sector in the track width direction. Then, the pattern is followed up, thereby obtaining both a full-track profile and a micro-track profile. A variation of a position signal is detected from this profile, thereby creating a table for correcting the non-linearity error of the position signal. Consequently, the distribution of the write/read-back property is measured, thereby enabling the track density to be improved. Furthermore, a variation of the position signal caused by a property variation of the head read-back element is detected and corrected, thereby enabling a high reliability and a high track density to be realized for the object magnetic recording disk apparatus.
    Type: Grant
    Filed: February 17, 2000
    Date of Patent: October 29, 2002
    Assignee: Hitachi, Ltd.
    Inventors: Takehiko Hamaguchi, Futoshi Tomiyama, Hideki Zaitsu, Hisashi Takano
  • Patent number: 6469862
    Abstract: A read channel network of a magnetic data storage device receives analog signals representative of user data and servo data, wherein the servo data is usable to position a read/write magnetic head. The servo data is separately processed within the read channel network to improve the signal to noise ratio of the user data signal and, thereby, permit improved positioning accuracy of the read/write head within the magnetic data storage device. The servo signal applied to a multiplier along with an oscillating signal reference signal to produce a sideband signal, which is passed through a bandpass filter having a bandwidth about that of the sideband signal and having a center frequency substantially the same as that of the sideband signal. Additionally, the signal output by the bandpass filter is processed by an envelope detector, and then by an A/D converter and digital filter to produce a digital signal representative of the servo signal.
    Type: Grant
    Filed: March 2, 1999
    Date of Patent: October 22, 2002
    Assignee: Guzik Technical Enterprises
    Inventors: Anatoli B. Stein, Ufuk Karaaslan, Ilia M. Bokchtein
  • Patent number: 6445526
    Abstract: In a reproducing apparatus, an equalizing system including a plurality of elements to be controlled is arranged to have its equalizing characteristic simply variable by controlling, with a single parameter, the plurality of elements to be controlled. Further, circuit characteristics of the equalizing system which are based on resonance frequencies and quality factors (Q) are controlled by controlling the resonance frequencies and the quality factors (Q) through the control performed with the single parameter over the plurality of elements to be controlled.
    Type: Grant
    Filed: November 21, 1997
    Date of Patent: September 3, 2002
    Assignee: Canon Kabushiki Kaisha
    Inventors: Kiwamu Kobayashi, Tatsuya Naitoh
  • Patent number: 6433949
    Abstract: A head for writing a plurality of bands. The bands have magnetic transitions onto a magnetic media (110). The magnetic media (110) travels in a preselected direction. The head includes a body support structure (100) and a plurality of write elements (120). The write elements (120) have a fixed alignment in the body support structure (100) that is substantially perpendicular relative to the travel direction of the magnetic media (110).
    Type: Grant
    Filed: July 7, 2000
    Date of Patent: August 13, 2002
    Assignee: Design & Test Technology, Inc.
    Inventors: Michael E. Murphy, Lawrence J. Tucker
  • Patent number: 6407874
    Abstract: A method and apparatus are provided for detection of the presence of slider airbearing resonance using surface analysis test (SAT) primary defect list (P-list) data. The P-list in the disk drive is selected. Checking for a cluster threshold of adjacent tracks within a sector to identify a SAT cluster is performed. Responsive to identifying the SAT cluster, checking for multiple defects on some tracks within the SAT cluster is performed. Responsive to identifying multiple defects on some tracks within the SAT cluster, the SAT cluster is converted to a binary matrix map. A histogram is generated for the binary matrix map. The harmonic magnitude content of the histogram from harmonics centered about a predetermined slider airbearing resonance frequency is identified.
    Type: Grant
    Filed: March 30, 2000
    Date of Patent: June 18, 2002
    Assignee: International Business Machines Corporation
    Inventors: Gordon James Smith, Hal Hjalmar Ottesen
  • Patent number: 6404576
    Abstract: A plurality of patterns are formed so that each is deviated slightly from another in each sector in the track width direction. Then, the pattern is followed up, thereby obtaining both a full-track profile and a micro-track profile. A variation of a position signal is detected from this profile, thereby creating a table for correcting the non-linearity error of the position signal. Consequently, the distribution of the write/read-back property is measured, thereby enabling the track density to be improved. Furthermore, a variation of the position signal caused by a property variation of the head read-back element is detected and corrected, thereby enabling a high reliability and a high track density to be realized for the object magnetic recording disk apparatus.
    Type: Grant
    Filed: January 12, 2000
    Date of Patent: June 11, 2002
    Assignee: Hitachi, Ltd.
    Inventors: Takehiko Hamaguchi, Futoshi Tomiyama, Hideki Zaitsu, Hisashi Takano
  • Patent number: 6400521
    Abstract: Magnetic tape recording apparatus comprising a plurality of recording heads for recording digital signals onto a magnetic tape, the recording heads being arranged in a matrix-type structure; and a control unit for electrically compensating for different magnetic properties of the recording heads, the control unit comprising controllable current sources connected to each of the recording heads; at least one non-volatile memory in which is permanently stored individually determined and pre-set magnetizing current values individually corresponding to a particular recording head; and common controller circuit for selectively activating the current sources and the current values stored in the non-volatile memory in dependence on the digital signals to be recorded, wherein upon selection the recording heads are supplied with the stored values of the magnetizing current assigned to them.
    Type: Grant
    Filed: July 25, 1996
    Date of Patent: June 4, 2002
    Assignee: Deutsche Thomson-Brandt GmbH
    Inventor: Jürgen Kaaden
  • Patent number: 6400517
    Abstract: A magnetic media processing device including an encoder for producing an output for a predetermined distance in a conveyance distance of a magnetic media on conveyance, a road circuit device for reading magnetic data stored in the magnetic media in synchronizing the output from the encoder to be processed as to its waveforms to produce read data, and an arithmetic device for converting a data length to data of a distance based on a time component of a data length of the read data of the read circuit device by employing the output signal from the encoder to read data based on distance data, wherein the arithmetic device compensates the process delay time in a time component of read data produced from the read circuit device when the arithmetic device converts the data length into the data of distance.
    Type: Grant
    Filed: July 14, 2000
    Date of Patent: June 4, 2002
    Assignee: Omron Corporation
    Inventor: Hiroshi Murao
  • Patent number: 6396652
    Abstract: Disclosed is a head loading/unloading type disk drive of retracting a head to a ramp by a reserve power supply upon power down of a main power supply. An unloading control system drives a VCM using a low-level voltage from the reserve power supply until the head reaches the ramp immediately upon power down of the main power supply. After the head reaches the ramp, the system applies a high-level voltage from the reserve power supply. The reserve power supply is made up of a rectifier for converting the back EMF of an SPM into a DC voltage. When a retract circuit detects power down of the main power supply, the DC voltage from the rectifier is limited to a low-level constant voltage by a constant voltage circuit, and applied to the VCM. When a ramp collision determining circuit determines collision of the head against the ramp, it controls the voltage applied to the VCM from the low-level voltage to a high-level voltage.
    Type: Grant
    Filed: August 11, 1999
    Date of Patent: May 28, 2002
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hidetoshi Kawachi, Koji Osafune
  • Patent number: 6392830
    Abstract: The present invention provides a system, method and data format wherein a redundant sync byte or group of sync bytes is provided in a data sector at a distance sufficient to isolate the redundant sync byte from the primary sync byte in the event of multiple byte defects. In a first embodiment, a redundant sync byte, or group of sync bytes, is provided in the AGC field preceding the primary sync region. Upon failure to detect the primary sync byte, an attempt is made on a subsequent revolution to read the secondary sync byte, either by holding the AGC gain prior to reaching the data block, or initiating an “early read” just prior to reaching the data block. In a second embodiment of the invention, the redundant sync byte is provided within the data field subsequent to the primary sync region. On failing to detect the primary sync byte, the secondary sync byte can be read immediately or can be postponed until a subsequent revolution.
    Type: Grant
    Filed: August 11, 2000
    Date of Patent: May 21, 2002
    Assignee: International Business Machines Corporation
    Inventor: Daniel James Malone, Sr.
  • Patent number: 6392832
    Abstract: A magnetic recording method using a magnetic head to record information in an information recording medium and read the information recorded on the information recording medium is such that the temperature of a portion of the information recording medium on or from which information is recorded or read is changed in order to record or read information. A disk device having the ability to record and read information comprises a magnetic head for recording information by applying a given magnetic field to an information recording medium and reading the information from the information recording medium; and a temperature changing mechanism for changing the temperature of a portion of the information recording medium on or from which information is recorded or read. The magnetic head is moved to the portion of the medium in which a temperature change is produced by the temperature changing mechanism, whereby information is recorded or read.
    Type: Grant
    Filed: March 25, 1998
    Date of Patent: May 21, 2002
    Assignee: Fujitsu Limited
    Inventors: Mitsumasa Oshiki, Seiya Ogawa
  • Patent number: 6388830
    Abstract: Apparatus and method for a head switching operation utilizing an automatic dummy load in a disc drive. A preamplifier circuit sequentially selects head positions and applies corresponding bias currents. A sequence control circuit automatically diverts the path of a first bias current from a head selection circuit to a dummy load after detecting an input of a second head location value into a buffer, and before the input is complete. After a bias current value for the second head is written into the buffer, the sequence control automatically deasserts the path to the dummy load after a predetermined time interval. The second bias current is then applied to the second head.
    Type: Grant
    Filed: July 30, 1999
    Date of Patent: May 14, 2002
    Assignee: Seagate Technology LLC
    Inventors: Robert Matousek, Timothy T. Walker
  • Patent number: 6388828
    Abstract: A method and apparatus for recording an information on magnetic recording tracks, called camera tracks, formed on a photographic negative film while relative movement is caused between the photographic negative film and a magnetic head. When the magnetic head is located in an information recording region of the camera tracks, a signal of the information representing photographing conditions of each image frame such as the aspect ratio of each frame, exposure amount at the time of photographing, information on a light source, etc., is output to the magnetic head via a modulator and a recording current amplifier. When the magnetic head is located in an non-recording region of the camera tracks, direct current having a magnitude substantially equal to the optimal recording current of the magnetic head or alternating current having the frequency which is not less than 5 times the frequency of the signal is output to the magnetic head via the modulator and the recording current amplifier.
    Type: Grant
    Filed: September 9, 1996
    Date of Patent: May 14, 2002
    Assignee: Fuji Photo Film Co., Ltd.
    Inventor: Tadashi Uekusa
  • Patent number: 6381083
    Abstract: In a recording/playback system, increased information is achieved by 4 level biased magnetic recording where the maximum amplitude 4 level recording signal drives the medium's magnetization into a nonlinear region of its transfer function. The bias does not eliminate distortion at the maximum signal input level, however the system's signal to noise ratio is improved due to an increase in the amplitude of the playback signal resulting from the increased recording level. The nonlinear mapping capability of a neural network provides equalization of playback signals distorted due to the record/playback nonlinearity. The 4 level recorded signals provide a factor of 2 in information storage compared to binary recording, and quadrature amplitude modulation (QAM) combined with the 4 level recording technique provides an additional factor of 2, for a factor of 4 in the information content stored.
    Type: Grant
    Filed: July 30, 1999
    Date of Patent: April 30, 2002
    Assignee: Applied Nonlinear Sciences, LLC
    Inventors: Henry D. I. Abarbanel, James U. Lemke, Lev S. Tsimring, Lev N. Korzinov, Paul H. Bryant, Mikhail M. Sushchik, Nikolai F. Rulkov
  • Patent number: 6381084
    Abstract: A sequencer overrun prevention method includes the steps of: initializing a sequencer; reading a timer value indicating when the sequencer begins operation; calculating a sequencer halting point by adding a predetermined time constant to the timer value; determining whether the sequencer operates at the sequencer halting point; and forcibly halting the sequencer when the sequencer operates at the sequencer halting point. The predetermined time constant is represented by T in the expression: T=(N)×(time required for one disk revolution)×(timer frequency), where N is indicative of a maximum number of detected indices and is greater than or equal to two. According to this method, the overhead time of a microprocessor can be reduced and sequencer overrun is prevented.
    Type: Grant
    Filed: April 25, 1996
    Date of Patent: April 30, 2002
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Hack-bin Kim
  • Patent number: 6381082
    Abstract: An arrangement for reading information from a record carrier, such as in a HDD, include a read head (Rmr1), an amplifier (74) for amplifying the signal read by the read head, an equalizer (76) for equalizing the signal read by the read head, and a bit detector (80) for detecting bits in the signal read by the read head. The invention, the arrangement further comprises a DC correction unit (78) for subtracting a correction value from an input signal in response to an error signal so as to obtain a DC corrected output signal. The bit detector (80) detects a sequence of bits based in the DC corrected output signal. Further, an error signal generating unit (82,83,85) is present for generating the error signal in response to the DC corrected output signal and the sequence.
    Type: Grant
    Filed: November 12, 1999
    Date of Patent: April 30, 2002
    Assignee: U.S. Philips Corporation
    Inventors: Johannes O. Voorman, Johannes W. M. Bergmans
  • Patent number: RE37817
    Abstract: An arrangement for recording an information signal in a track (T0, T1, . . . ) on a record carrier (1), includes an input (20) for receiving the information signal, signal processing circuitry (21) for processing the information signal such that it can be recorded in the track, counting device (23) for counting and for generating an array of subsequent different count signals and for supplying the count signals to an output (24), recording apparatus (25, 26, 27) having at least one recording head (26) for recording the processed information signal in a track on the record carrier, and for recording the count signals in a track on the record carrier and a transport apparatus (34,35) for transporting the record carrier with a certain transport velocity (vt) in a longitudinal direction of the record carrier.
    Type: Grant
    Filed: July 25, 2000
    Date of Patent: August 13, 2002
    Assignee: Koninklijke Philips Electronics N.V.
    Inventors: Pieter G. Van Leeuwen, Albert M. A. Rijckaert