Patents Examined by Dan I Davidson
  • Patent number: 6930844
    Abstract: A method for measuring spacing between a head and a storage medium is provided. The method includes obtaining a sample of a readback signal from a sequence of data stored on the storage medium using the head. An amplitude of the readback signal for a plurality of frequencies is calculated. Additionally, the method includes providing a measurement indicative of spacing between the head and the storage medium based on the amplitude.
    Type: Grant
    Filed: May 19, 2003
    Date of Patent: August 16, 2005
    Assignee: Seagate Technology LLC
    Inventors: Nan-Husing Yeh, Don R. Bloyer, John W. Dykes
  • Patent number: 6927929
    Abstract: A position error signal amplitude indicative of the distance between an expected position of a magnetic head relative to the track centerline of a magnetic data storage and retrieval system and an actual position of the magnetic head relative to the track centerline is detected and filtered. The signal is filtered to generate a sway mode signal amplitude indicative of an oscillation of the actual position of the magnetic head relative to the track centerline in the frequency range of the filter. The absolute value of the sway mode signal amplitude is then determined. If the absolute value of the sway mode signal exceeds a predetermined threshold value that correlates to a high probability of impending a head-disk crash, a warning signal is propagated.
    Type: Grant
    Filed: September 24, 2003
    Date of Patent: August 9, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Karl Gong, Hal Hjalmar Ottesen, Gordon James Smith
  • Patent number: 6920001
    Abstract: A method of categorizing magnitudes of thermal asperities in a read-back signal of a data storage system includes receiving the read-back signal from a location containing a thermal asperity. A peak magnitude signal is generated from the read-back signal. A threshold signal is generated using a variable threshold generator. The peak magnitude signal is compared to the threshold signal and a magnitude of the thermal asperity is categorized as a function of the comparison.
    Type: Grant
    Filed: June 12, 2003
    Date of Patent: July 19, 2005
    Assignee: Seagate Technology LLC
    Inventors: Teng Hou Sebastian Chua, Myint Ngwe, Lan Xia, Beng Wee Quak, Quek Leong Choo
  • Patent number: 6914737
    Abstract: In an apparatus for recording and regenerating data, a pass metric is calculated based on a likelihood converted from a previous calculation result iteratively until all pass metrics of the same data recorded many times on a recording medium are calculated, and then data recorded on the recording medium is decoded.
    Type: Grant
    Filed: October 8, 2003
    Date of Patent: July 5, 2005
    Assignee: Fujitsu Limited
    Inventors: Masakazu Taguchi, Akihiro Itakura, Akiyoshi Uchida
  • Patent number: 6914735
    Abstract: In a manufacturing method for a magnetic recording medium, when the length of a ferromagnetic thin film on a master information carrier corresponding to the length between a pair of magnetization transition regions adjacent to each other is A in magnetization information recorded onto a magnetic recording medium, the film thickness of the ferromagnetic thin film is t and A/t is k, k is set from not less than 0.8 to not more than 8.
    Type: Grant
    Filed: October 2, 2002
    Date of Patent: July 5, 2005
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Taizou Hamada, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 6882489
    Abstract: A method and apparatus for dynamically detecting write fault errors is provided. According to the invention, transducer head control parameters are adjusted according to observed events. For instance, off-track events of a certain magnitude may trigger the implementation of a severe shock timer, which lengthens the delay between the off-track event and allowing write operations to resume, as compared to the standard off-track timer. According to another embodiment of the present invention, a lower write fault threshold is implemented following an off-track event of sufficient magnitude. According to yet another embodiment of the present invention, the average or accumulated position error of the transducer head is monitored, and a lower write fault threshold implemented if the average position error exceeds a threshold value.
    Type: Grant
    Filed: August 15, 2000
    Date of Patent: April 19, 2005
    Assignee: Maxtor Corporation
    Inventors: Don Brunnett, John Purkett, Bruce Liikanen
  • Patent number: 6882488
    Abstract: A magnetic recording method uses a patterned perpendicular magnetic recording medium where each magnetic block or island contains a stack of individual magnetic cells to providing multilevel recording. Each cell in an island is formed of a material or set of materials to provide the cell with perpendicular magnetic anisotropy and is a single magnetic domain. Each cell is magnetically decoupled from the other cells in its island by nonmagnetic spacer layers. Thus each cell can have a magnetization (magnetic moment) in one of two directions (into or out of the plane of the layer making up the cell), and this magnetization is independent of the magnetization of the other cells in its island. This permits multiple magnetic levels or states to be recorded in each magnetic island.
    Type: Grant
    Filed: December 3, 2003
    Date of Patent: April 19, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Manfred Albrecht, Olav Hellwig, Guohan Hu, Bruce David Terris
  • Patent number: 6873483
    Abstract: A read clock circuit for a disk drive includes a phase-locked loop/voltage controlled oscillator (VFO/PLL) and a frequency synthesizer. The VFO/PLL receives a servo sector transition signal that is related to detected transitions in a servo sector field of a magnetic recording disk, and outputs a servo frequency signal that is synchronous to the servo sector transition signal. The frequency synthesizer receives the servo frequency signal and generates the read clock signal that is synchronous with the servo frequency signal. In a banded recording disk drive the frequency synthesizer generates a unique read clock signal for each data band.
    Type: Grant
    Filed: February 7, 2002
    Date of Patent: March 29, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Steven R. Hetzler, William John Kabelac
  • Patent number: 6870697
    Abstract: Devices and methods for generating a magnetic head-specific overshoot current which is combined with an alternating current waveform into a write current used by the magnetic head to store information on a magnetic medium. A processor analyzes the frequency of incoming write data and retrieves from a data table of an overshoot current amplitude and an overshoot current phase. This amplitude and phase information is sent to an overshoot current generator to generate an overshoot current that is responsive to the dynamic impedance properties of a magnetic write head during operation. The data table may have information related to one or many write heads, and the data table may be further subdivided based on additional dynamic characteristics of a write head that may affect the impedance thereof.
    Type: Grant
    Filed: June 10, 2003
    Date of Patent: March 22, 2005
    Assignee: Hitachi, Ltd.
    Inventors: Hiroshi Ikekame, Takeo Yamashita
  • Patent number: 6865042
    Abstract: The present invention involves a recordable disk having a first plurality of S1 servo sample wedges in a first servo zone at an outermost position on the disk, a second plurality of S2 servo sample wedges in a second servo zone which is radially adjacent the first servo zone, and a third plurality of S3 servo sample wedges in a third servo zone which is radially adjacent the second servo zone. The S1 servo sample wedges of the first plurality are equally spaced apart circumferentially around the disk by a first angle ?1, the S2 servo sample wedges of the second plurality are equally spaced apart circumferentially around the disk by a second angle ?2=?1*N1, and the S3 servo sample wedges of the third plurality are equally spaced apart circumferentially around the disk by a third angle ?3=?2*N2.
    Type: Grant
    Filed: February 13, 2002
    Date of Patent: March 8, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands N.V.
    Inventors: George Anthony Dunn, Mantle Man-Hon Yu
  • Patent number: 6865041
    Abstract: A method and apparatus for servowriting using a unipolar write current is disclosed. A track for writing a servo pattern is determined and the servo pattern is written using a unipolar write current pulse. The writing of the servo pattern using the unipolar write current pulse creates a servo pattern having less of an erase band and wider track width than if the servo pattern was produced by a bipolar write current pulse. The unipolar write current pulse is applied across a write gap formed by a first pole and a second pole, and wherein a field extension next to the first pole extends further and creates a narrower side erase band than the field proximate to the second pole. The write current pulse width is controlled to set a magnetization length in the servo pattern created in the disk. Analog characteristic of a digital control signal in a variable width pulse generator is set to control a width of the write current pulse to control a magnetization length in the servo pattern created on the disk.
    Type: Grant
    Filed: February 29, 2000
    Date of Patent: March 8, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Thomas Claude Arnoldussen, Roger William Wood, Ju-Hi John Hong
  • Patent number: 6865043
    Abstract: Special fields for error recovery are provided in data set information tables of data sets written with synchronized transactions. If a transaction only partially fills a data set, that data set is rewritten in a succeeding data set, appending the next transaction. A moving access point in the table identifies the appended transaction, allowing the rewritten transaction to be skipped during read recovery. The table provides recovery trails by providing a thread to tie the data sets together, the status of the data set, and pointers, such as identifying the wrap of the immediately succeeding data set.
    Type: Grant
    Filed: November 14, 2002
    Date of Patent: March 8, 2005
    Assignee: International Business Machines Corporation
    Inventors: Toshimi Ataku, Paul Merrill Greco, Hiroshi Itagaki, Glen Alan Jaquette, Hironobu Nagura, Toshiyuki Shiratori
  • Patent number: 6865044
    Abstract: A method for magnetic recording uses a fixed write current with thermal assistance to record on a patterned perpendicular magnetic recording medium. The patterned medium has magnetic blocks or islands, each of which contains a stack of individual magnetic cells to provide multilevel recording. Each cell in an island is formed of a material or set of materials to provide the cell with perpendicular magnetic anisotropy and is a single magnetic domain. Each cell is magnetically decoupled from the other cells in its island by nonmagnetic spacer layers. Thus each cell can have a magnetization (magnetic moment) in one of two directions (into or out of the plane of the layer making up the cell), and this magnetization is independent of the magnetization of the other cells in its island. This permits multiple magnetic levels or states to be recorded in each magnetic island.
    Type: Grant
    Filed: December 3, 2003
    Date of Patent: March 8, 2005
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Manfred Albrecht, Olav Hellwig, Guohan Hu, Bruce David Terris
  • Patent number: 6856479
    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 29, 2002
    Date of Patent: February 15, 2005
    Assignee: International Business Machines Corporation
    Inventors: Glen Alan Jaquette, Paul Merrill Greco, James Mitchell Karp
  • Patent number: 6842303
    Abstract: A magnetic recording and/or reproducing apparatus includes an equalization section for equalizing a signal sequence which is reproduced from a magnetic recording medium and outputting an equalized waveform, and a conversion section for converting the equalized waveform into a maximum likelihood sequence by carrying out metric calculation based on average values of the equalized waveform.
    Type: Grant
    Filed: August 2, 2001
    Date of Patent: January 11, 2005
    Assignee: Fujitsu Limited
    Inventors: Kazuhito Ichihara, Hiroaki Ueno
  • Patent number: 6833970
    Abstract: A data reader reads a medium holding user and non-user data that holds information relating to the user data. The reader has a read head that generates a data signal comprising user and non-user data. The user data is arranged into plural sets interspersed with the non-user data that identifies the user data within the sets. Processing circuitry receives and processes the data signal and obtains the user data from the data signal by using the non-user data to identify the user data within the data signal. The data reader is particularly suitable in situations having re-writes and overwrites.
    Type: Grant
    Filed: July 31, 2001
    Date of Patent: December 21, 2004
    Assignee: Hewlett-Packard Company
    Inventor: Jonathan Peter Buckingham
  • Patent number: 6826003
    Abstract: A disk drive is disclosed comprising a disk and a head actuated radially over the disk. A pattern detector detects a predetermined pattern in write data to be written to the disk, and in response, adjusts a write current overshoot in a write current applied to the head.
    Type: Grant
    Filed: January 31, 2002
    Date of Patent: November 30, 2004
    Assignee: Western Digital Technologies, Inc.
    Inventor: Jai N. Subrahmanyam
  • Patent number: 6822818
    Abstract: A hard disk drive and magnetic medium including a servo area, a data area divided into a plurality of sector blocks and at least one micro-servo area disposed between two sector blocks. There may be a micro-servo area immediately preceding each of the plurality of sector blocks. The micro-servo areas include an address mark and a track parity check code that allow the detection of an external shock that causes the recording (write) head to skip to an adjacent track in the hard disk medium. The micro-servo area is smaller than the servo areas, and various numbers of different track parity check codes can be used for different resolution of shock detection. An acceleration sensor may also be provided to detect larger external shocks. By detecting various external shocks with improved accuracy, and aborting the recording operation of data if an external shock is detected, the corruption of data in adjacent tracks is substantially reduced to improve disk drive performance.
    Type: Grant
    Filed: August 2, 2001
    Date of Patent: November 23, 2004
    Assignee: Hitachi, LTD
    Inventors: Takehiko Hamaguchi, Kyo Akagi, Hisashi Takano, Takayuki Ichihara
  • Patent number: 6819513
    Abstract: A disk drive which incorporates separate actuators for each recording head so as to only place required recording heads over the recording media of multiple surface hard disk drives. The reduction in recording heads that are placed over the recording media reduces drag on the rotating disk holding the recording media and thereby reduces the power consumption. Reducing the number of recording heads over the recording media also reduces damage to the recording media surfaces in the event of a physical shock to the drive since inactive transducer heads are not in a position to damage the recording media.
    Type: Grant
    Filed: January 2, 2002
    Date of Patent: November 16, 2004
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Timothy J. Chainer, Anthony P. Praino
  • Patent number: 6813106
    Abstract: A preconditioning process for contact printing of a reference servo pattern on storage media. The preconditioning process presets the magnetization of problematic grains, that is, grains that typically contribute to spurious subpulses on the media, in the direction of the printing field.
    Type: Grant
    Filed: May 1, 2002
    Date of Patent: November 2, 2004
    Assignee: Maxtor Corporation
    Inventor: Michael Mallary