Distinct Servo Sector Patents (Class 360/77.08)
  • Patent number: 7457071
    Abstract: An embodiment of the present invention comprises a method of writing product servo sectors to a disk of a disk drive. The disk comprises a plurality of spiral tracks each having a high frequency signal interrupted at a predetermined interval by a sync mark. The head internal to the disk drive is used to read the spiral tracks to generate a read signal which is processed to detect the sync marks. An aberration is detected in the detected sync marks in order to locate an initial radial location of the head with respect to the disk. The read signal representing the high frequency signal in the spiral tracks is processed to generate a position error signal (PES) used to maintain the head along a substantially circular target path while using the head internal to the disk drive to write the product servo sectors along the circular target path.
    Type: Grant
    Filed: August 8, 2006
    Date of Patent: November 25, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventor: Edgar D. Sheh
  • Patent number: 7453663
    Abstract: A disk drive includes a rotatable disk, a transducer, an actuator, and a controller. The disk includes a first servo burst pattern in a first radial spoke of the disk, and a second servo burst pattern in a second radial spoke of the disk. The first and second servo burst patterns are radially offset from each other and are associated with a plurality of data tracks extending through the first and second radial spokes. The transducer is configured to read the first and second servo burst patterns on the disk to generate a servo burst signal. The actuator is configured to position the transducer relative to the disk. The controller is configured to control positioning of the transducer relative to the tracks on the disk based on the servo burst signal.
    Type: Grant
    Filed: December 14, 2004
    Date of Patent: November 18, 2008
    Assignee: Maxtor Corporation
    Inventors: Mourad Benakli, Ara Patapoutian, Laurent Duchesne
  • Patent number: 7453664
    Abstract: A magnetic disk apparatus is configured so as to read trace information from a discrete track recording medium recording the trace information for making a servo locus of a magnetic head trace the center line of physical tracks and control the servo locus of the magnetic head onto the center line of the physical tracks.
    Type: Grant
    Filed: August 24, 2006
    Date of Patent: November 18, 2008
    Assignee: Fujitsu Limited
    Inventor: Takayuki Kawabe
  • Patent number: 7450336
    Abstract: A method is disclosed for determining fundamental-frequency repeatable runout (1FRRO) coefficients in a disk drive. The disk drive includes a transducer head, a rotating magnetic disk having a plurality of concentric data tracks defined by embedded servo wedges that provide position information, and an actuator coupled to the head. In the method, the head is caused to move in a substantially constant velocity motion across a selected portion of the tracks of the rotating magnetic disk in response to a control signal. The position information is read from the embedded servo wedges as the head moves across of the selected portion of the tracks. The 1FRRO coefficients are determined based on the position information read as the head moved in a substantially constant velocity motion across the selected portion of the tracks.
    Type: Grant
    Filed: October 31, 2006
    Date of Patent: November 11, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Zhi Wang, Jianghong Ding
  • Patent number: 7443622
    Abstract: A reliable magnetic recording medium is provided which comprises a servo signal unit portions formed in a concavo-convex shape, easily produced, and resistant to tracking error. Also provided are a magnetic recording/reproducing apparatus which incorporates the magnetic recording medium, and a stamper for manufacturing the magnetic recording medium with efficiency. The magnetic recording medium includes a recording layer divided into a plurality of data areas and a plurality of servo areas to record information. The recording layer is formed in a concavo-convex shape in each servo area, with a servo signal unit portions formed as either a convex portions or a concave portions of the concavo-convex shape. Of the servo signal unit portions, the burst signal unit portion for tracking is generally elliptical in shape when viewed from the direction of thickness.
    Type: Grant
    Filed: August 30, 2005
    Date of Patent: October 28, 2008
    Assignee: TDK Corporation
    Inventors: Akimasa Kaizu, Makoto Moriya, Yoshikazu Soeno
  • Publication number: 20080259489
    Abstract: A method of writing a servo pattern to a disk, wherein a servo pattern is generated in a processor. The generated servo pattern is then written to a disk. The servo pattern for a servo sector is preferably generated in a single routine.
    Type: Application
    Filed: September 14, 2006
    Publication date: October 23, 2008
    Applicant: XYRATEX TECHNOLOGY LIMITED
    Inventors: Keith R.C. Brady, Alistair M. Campbell, Mark J. Newland
  • Publication number: 20080259488
    Abstract: Embodiments of the invention include: a hard disk drive using a read track to position for writing to a write track and generating a position error signal (PES) based upon all four servo offset bursts used to disable writing when the PES exceeds a position error threshold; a preamplifier generating the PES from four bursts from a slider reading the read track to position when the write track is to be written, and methods of writing the write track using PES from four bursts of the read track that disables writing when the PES is above the position error threshold.
    Type: Application
    Filed: April 19, 2007
    Publication date: October 23, 2008
    Inventors: Chang-Ik Kang, Bong-Jin Lee
  • Patent number: 7440224
    Abstract: A disk drive includes a disk having a first servo burst written with advancing phase as a radial distance on the disk increases, and a second servo burst written with decreasing phase as a radial distance on the disk increases, and a transducing head, and a read channel. The disk drive also includes an element for shifting the phase of the signal produced by the first burst pattern with respect to the signal produced by the second burst pattern by an amount sufficient to substantially cancel distortion in a signal produced by the first servo burst with distortion in a signal produced by the second servo burst when the signal from the first servo burst is added to the signal from the second servo burst.
    Type: Grant
    Filed: January 23, 2006
    Date of Patent: October 21, 2008
    Assignee: Toshiba Corporation
    Inventors: Richard M. Ehrlich, David Rutherford
  • Publication number: 20080253018
    Abstract: A method determines RW head radial position relative to tracks within a magnetic data disc. This involves sensing both a S-burst signal and a P-burst signal with the RW head. The S-burst signal and P-burst signal are associated with a two-burst servo pattern on the magnetic disc. The S-burst pattern has a phase that remains constant radially across tracks within the magnetic disc. The P-burst has a second phase that rotates radially across tracks within the magnetic disc. By determining a phase difference between a sensed S-burst signal and P-burst signal, it is possible to determine the RW head radial position relative to the tracks on the magnetic disc.
    Type: Application
    Filed: June 25, 2008
    Publication date: October 16, 2008
    Applicant: BROADCOM CORPORATION
    Inventors: Benjamin Geunbae Ryu, Ara W. Nazarian
  • Patent number: 7436611
    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.
    Type: Grant
    Filed: March 17, 2006
    Date of Patent: October 14, 2008
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Yasutaka Nishida, Takehiko Hamaguchi, Hideki Sawaguchi, Hisashi Takano
  • Patent number: 7433149
    Abstract: A disk drive stores overhead information corresponding to multiple servo sectors within a dedicated data sector in a customer data region of a data storage disk. The overhead information includes servo data for which the information content does not depend upon the physical location of the data on the disk surface. During a data storage operation, the overhead data is read from the dedicated data sector and stored in a buffer memory within the disk drive. A portion of the overhead data is then retrieved from the buffer memory for each servo sector subsequently traversed by the transducer for use in performing a data processing task related to the servo sector.
    Type: Grant
    Filed: January 30, 2006
    Date of Patent: October 7, 2008
    Assignee: Maxtor Corporation
    Inventor: Edward M. Gostling
  • Publication number: 20080239557
    Abstract: A method of self servo-writing servo information to a plurality of disk surfaces in a disk drive that includes writing servo information to a plurality of disk surfaces in a first direction, writing servo information to a plurality of disk surfaces in a second direction, and determining an amount of overlap to be written on a reference surface with the reference head that will produce an overlap of servo information on each of the surfaces in the disk drive to which servo information is to be written. The method also includes switching to different tables when seeking across the overlap or border areas.
    Type: Application
    Filed: March 30, 2007
    Publication date: October 2, 2008
    Inventor: Anton Gerasimov
  • Publication number: 20080239558
    Abstract: Methods and apparatus for controlling the duration of a pulse in a hard drive write system are disclosed. A disclosed method comprises generating a current pulse, reducing the current of the pulse and conveying a portion of the current pulse to a hard drive write system. In addition, a method is disclosed whereby a portion of the current pulse is truncated.
    Type: Application
    Filed: January 17, 2008
    Publication date: October 2, 2008
    Inventors: Jeremy Robert Kuehlwein, Marius Vicentiu Dina
  • Publication number: 20080239555
    Abstract: A method for servo correction includes determining a first wedge offset reduction field value for a read element from information in a servo burst area of a wedge on a disk, storing the first wedge offset reduction field value, determining a second wedge offset reduction field value for the read element from information in the servo burst area of the wedge on the disk, storing the second wedge offset reduction field value, and estimating an offset value of the read element from a desired track on the disk using at least one of the first wedge offset reduction value or second wedge offset reduction field value.
    Type: Application
    Filed: March 30, 2007
    Publication date: October 2, 2008
    Applicant: TOSHIBA AMERICA INFORMATION SYSTEMS, INC.
    Inventors: Richard M. Ehrlich, Thorsten Schmidt
  • Publication number: 20080239556
    Abstract: A method for determining a position error signal in a disk drive includes writing a servo signal that has a variable offset from a track center for a plurality of concentric tracks in a servo wedge on a disk surface, forming a spiral servo track, observing the offset values for the servo signal in the servo wedges at a first of the plurality of tracks, and observing the offset values for the servo signal in the servo wedges at a second of the plurality of tracks. The method also includes determining the first error amounts from the offset values at the first of the plurality of tracks, and determining the second error amounts from the offset values at the second of the plurality of tracks. If the first error amounts and the second error amounts are equal, using one of the first or second error amounts as a correction update to a head non-linearity look-up table.
    Type: Application
    Filed: March 30, 2007
    Publication date: October 2, 2008
    Inventors: James V. Wiseman, Gary W. Calfee
  • Patent number: 7430082
    Abstract: A new technique for Hard Disk Drive (HDD) servo-burst demodulation is provided. A 4-samples per dibit Discrete Fourier Transform (DFT) amplitude estimation is used to calculate the read-head servo-position error signal. Comparatively, the conventional method of burst demodulation—called burst integration—typically uses more than 8 samples/dibit. Consequently, the new 4-samples/dibit DFT burst-demodulation scheme requires fewer samples per dibit than does burst integration, thus reducing the disk space occupied by the burst data while increasing the performance as compared to burst integration. Furthermore, the DFT scheme does not require the samples to be synchronized to any particular points of the servo burst, and can include an averaging algorithm that further improves performance for a given Signal to Noise Ratio (SNR). Moreover, the same sample-clocking circuit that detects the Gray Code servo information can also implement the DFT burst-demodulation scheme to demodulate the servo burst.
    Type: Grant
    Filed: November 5, 2001
    Date of Patent: September 30, 2008
    Assignee: STMicroelectronics, Inc.
    Inventors: Fereidoon Heydari, Hakan Ozdemir
  • Patent number: 7414809
    Abstract: In accordance with various embodiments, initial servo data are written to a storage medium as a series of radially overlapped spiral segments. Final servo data are thereafter written to the medium while concurrently servoing on said overlapped segments.
    Type: Grant
    Filed: May 18, 2007
    Date of Patent: August 19, 2008
    Assignee: Maxtor Corporation
    Inventors: S. Craig Smith, Stan Shepherd, Yu Sun, Yuan Roy Chen, Lin Guo
  • Patent number: 7408733
    Abstract: Embodiments of the invention increase the convenience of a magnetic disk drive for portable use by shortening a period of time required to record a large amount of data, and by increasing the reproduction time, in the magnetic disk drive. In one embodiment, an area between servo data parts is interpolated by servo data parts, each of which stores a burst signal, so that the allocation density of a burst signal is made k times. At the time of write operation in which data is written, only the servo data parts are made use of to perform the servo control while a disk is driven at high rotational speed so as to reduce the recording time. At the time of read operation in which data is reproduced, the servo data parts are made use of to ensure the required precision of the servo control at low rotational speed that is 1/k of the rotational speed at the time of write operation. The reproduction at low rotational speed enables the reduction in power consumption.
    Type: Grant
    Filed: April 7, 2006
    Date of Patent: August 5, 2008
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Naoki Satoh, Yoshiteru Ishida, Yoshiju Watanabe, Terumi Takashi
  • Publication number: 20080180825
    Abstract: A servo system for detecting and demodulating servo data is disclosed. In illustrated aspects, a demodulation circuit or portion includes a correlator component configured to output a correlation of a sequence of equalized channel samples with a sequence of correlator weight derived based on at least one mapped channel sequence. A decision component, for example a threshold detector uses the correlation results to output a data bit symbol based upon the correlation of the sequence of equalized channel samples to the at least one mapped channel sequence.
    Type: Application
    Filed: January 31, 2007
    Publication date: July 31, 2008
    Applicant: Seagate Technology LLC
    Inventors: Mehmet F. Erden, Richard L. Keizer
  • Patent number: 7405893
    Abstract: A data storage medium and data storage system with improved efficiency of formatting are provided. One illustrative embodiment of the present invention pertains to a data storage medium. The data storage medium includes a first zone having servo information written with a first frequency, a second zone having servo information written with a second frequency, and a guard band disposed between the first zone and the second zone. The use of different frequencies in different zones contributes to optimizing the properties of the data storage medium, and the guard band contributes to optimizing the usage of the different zones.
    Type: Grant
    Filed: September 21, 2005
    Date of Patent: July 29, 2008
    Assignee: Seagate Technology LLC
    Inventors: Qiang Bi, KianKeong Ooi, TaiVie Chiang, WingKong Chiang, Edmun ChianSong Seng, Jimmy Pang, BengWee Quak, UttHeng Kan, Xiong Liu, Ricardo SoonLian Lim, Patrick TaiHeng Wong, MingZhong Ding, WeiMing Yeow
  • Patent number: 7405899
    Abstract: A method determines RW head radial position relative to tracks within a magnetic data disc. This involves sensing both a S-burst signal and a P-burst signal with the RW head. The S-burst signal and P-burst signal are associated with a two-burst servo pattern on the magnetic disc. The S-burst pattern has a phase that remains constant radially across tracks within the magnetic disc. The P-burst has a second phase that rotates radially across tracks within the magnetic disc. By determining a phase difference between a sensed S-burst signal and P-burst signal, it is possible to determine the RW head radial position relative to the tracks on the magnetic disc.
    Type: Grant
    Filed: April 18, 2006
    Date of Patent: July 29, 2008
    Assignee: Broadcom Corporation
    Inventors: Benjamin Geunbae Ryu, Ara W. Nazarian
  • Patent number: 7403353
    Abstract: The invention is directed to a magnetic recording/reproducing system wherein each burst pattern in discrete media is configured in a substantially trapezoidal shape (truncated quadrangular pyramid shape, and which satisfies given relations between W1, W2, Tp and Wr. W1 is the upper side of the trapezoidal shape in the track width direction, which corresponds to the surface of said convex-form magnetic recoding layer, W2 is the lower side of the trapezoidal shape in the track width direction, which corresponds to the bottom surface of said convex-form magnetic layer, Tp is the data track pitch at the data information recording portion, and Wr is the read width of the magnetic head, so that loads on burst pattern shape in medium fabrication processes can be far more reduced and far more precise position error signals can be obtained.
    Type: Grant
    Filed: January 18, 2006
    Date of Patent: July 22, 2008
    Assignee: TDK Corporation
    Inventors: Katsumichi Tagami, Kazuya Shimakawa
  • Patent number: 7403355
    Abstract: On an information recording medium, a data track pattern and a servo pattern composed of a concave/convex pattern including a plurality of convex parts are formed on at least one surface of a substrate and respective concave parts in the concave/convex pattern are filled with non-magnetic material. In the concave/convex pattern that constructs the servo pattern, a unit convex part length along a direction of rotation of the substrate and a unit concave part length along the direction of rotation are set so that the ratio of the unit convex part length to the unit concave part length decreases from an inner periphery to an outer periphery of the information recording medium.
    Type: Grant
    Filed: August 31, 2005
    Date of Patent: July 22, 2008
    Assignee: TDK Corporation
    Inventors: Yoshikazu Soeno, Takahiro Suwa
  • Publication number: 20080170324
    Abstract: On a rotary-type magnetic recording medium, servo patterns are formed in servo pattern regions on one surface and the other surface of a disk-shaped substrate by patterns including recording regions and non-recording regions. In the servo pattern regions on both the one surface and the other surface, plural functional regions are defined in order in a direction of rotation of the magnetic recording medium. In the pattern formed in at least one region out of the plural functional regions on the one surface, the non-recording regions are formed at formation positions on the one surface corresponding to formation positions of the recording regions on the other surface and the recording regions are formed at formation positions on the one surface corresponding to formation positions of the non-recording regions on the other surface.
    Type: Application
    Filed: January 11, 2008
    Publication date: July 17, 2008
    Applicant: TDK CORPORATION
    Inventors: Shuichi OKAWA, Kazuhiro HATTORI, Makoto MORIYA
  • Patent number: 7400468
    Abstract: A hard disk drive with a circuit that provides a control signal to a voice coil motor to move a head across a disk. The disk drive includes a circuit that provides a control signal to the voice coil motor to move the head. The circuit also has a state predictor and an inversion filter that compute a vibration estimate used to detect a vibration in the drive. When a threshold vibration is detected a vibration estimate is combined with the control signal to compensate for the vibration. The circuit detects the vibration without the need for an accelerometer or other sensor.
    Type: Grant
    Filed: November 22, 2006
    Date of Patent: July 15, 2008
    Assignee: Samsung Electronics Co., Ltd.
    Inventors: Chang-Ik Kang, Yunfeng Li, Bong-Jin Lee
  • Patent number: 7397627
    Abstract: A head is moved in a lateral direction on the boundary between a separation track and a recording track on a recording medium. The separation track isolates the adjacent recording tracks from each other. A variation is detected in the output supplied from the head based on the recording track. Positional information indicating the position of the head is generated based on the variation. The output supplied from the head varies in response to the movement in the lateral direction, namely the elapsed time. The positional information can thus be generated based on the variation in the output. The generated positional information contributes to an accurate positioning in a facilitated manner. Moreover, information required to position the head can be omitted from the recording medium. The processes can be simplified in the production of the recording medium. The operation time can thus be shortened.
    Type: Grant
    Filed: May 31, 2005
    Date of Patent: July 8, 2008
    Assignee: Fujitsu Limited
    Inventors: Takahiro Imamura, Arata Ejiri, Yutaka Nakamura, Ken-ichi Itoh
  • Patent number: 7397630
    Abstract: A signal reproducing method reproduces servo information recorded on a recording medium by use of a head. A current calculation related to a current and an observer calculation related to a position and a velocity of the head are made based on reproduced servo information, and a current value for driving the head is calculated based on the above calculation result. Only computations which require a demodulation result of a present sample are made during a first time after demodulation of the position of the head to a time when the current value is output, and computations which require a demodulation result of a past sample are made during a second time other than the first time.
    Type: Grant
    Filed: February 6, 2007
    Date of Patent: July 8, 2008
    Assignee: Fujitsu Limited
    Inventor: Tomoaki Saito
  • Publication number: 20080158718
    Abstract: A magnetic recording medium enhances the quality of a reproducing signal. The magnetic recording medium has a servo pattern formed in a servo pattern area on at least one surface of a disk-shaped substrate by a concave/convex pattern having convex portions (recording areas) and concave portions (non-recording areas), and a data track pattern formed by the concave/convex pattern in a data recording area on the at least one surface of the disk-shaped substrate. In a state where recording data is not recorded in the data recording area, the convex portions in the servo pattern area are DC-magnetized, and the convex portions in the data recording area are AC-magnetized.
    Type: Application
    Filed: December 27, 2007
    Publication date: July 3, 2008
    Applicant: TDK Corporation
    Inventors: Tatsuhiro KOBAYASHI, Makoto MORIYA
  • Publication number: 20080151414
    Abstract: According to one embodiment, there is to provide a disk drive which calculates an error in the position of a head on the basis of concentric servo patterns. The disk drive has a disk medium on which spiral servo patterns are recorded and a read head which reads the spiral servo patterns from the disk medium. A servo controller reproduces a hexagonal burst signal from the spiral servo patterns read by the read head to generate position data associated with servo burst signals. The CPU uses the position data to perform a position error calculation.
    Type: Application
    Filed: November 19, 2007
    Publication date: June 26, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Toshitaka Matsunaga, Masahide Yatsu, Hideo Sado, Katsuki Ueda, Shouji Nakajima, Seiji Mizukoshi, Shinichirou Kouhara
  • Patent number: 7391583
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The read signal from the head is processed to detect a plurality of the sync marks in a spiral track crossing. A timing recovery measurement is generated in response to a selected one of the sync marks based on reliability metrics, wherein a servo write clock is synchronized in response to the timing recovery measurement. The read signal representing the high frequency signal in the spiral track crossing is processed to generate a position error signal (PES) used to maintain the head along a substantially circular target path while using the servo write clock to write product servo sectors along the circular target path.
    Type: Grant
    Filed: July 27, 2006
    Date of Patent: June 24, 2008
  • Patent number: 7388728
    Abstract: A perpendicular media recording (PMR) servo track writer (STW) system and method for writing servo sectors onto a disk is disclosed. The servo writer includes a head positioner to position a head of a head disk assembly (HDA) relative to a disk, wherein the head writes servo sectors onto the disk with a perpendicular flux. The servo writer includes a controller to control the head positioner such that the head writes servo sectors onto the disk from one of an inner diameter (ID) or an outer diameter (OD) of the disk to a middle diameter (MD) of the disk, respectively, followed by writing servo sectors between the other of the OD or the ID of the disk to the MD of the disk, respectively.
    Type: Grant
    Filed: September 22, 2006
    Date of Patent: June 17, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Teddy T. C. Chen, Jinsheng Bill Jang, Jie Yu, Masao Miyamura
  • Patent number: 7388729
    Abstract: A magnetic recording device includes a composite magnetic head, which includes a recording head and a reproduction head, and a magnetic recording medium. The magnetic recording medium includes a data region for recording data using the recording head, a mask pattern region in which an area in which servo information can be magnetically recorded and an area in which information cannot be magnetically recorded are formed in a predetermined pattern, and an initial positioning region in which a magnetic area and a nonmagnetic area that record information for positioning one of the recording head and the reproduction head in the mask pattern region.
    Type: Grant
    Filed: March 16, 2007
    Date of Patent: June 17, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Hiroaki Nakamura
  • Patent number: 7382568
    Abstract: A servo circuit includes a servo channel and a processor. The servo channel recovers servo data from servo wedges that identify respective data sectors on a data-storage disk. The processor detects one of the servo wedges on spin up of the disk, i.e., while the disk is attaining or after the disk attains an operating speed. By detecting a servo wedge instead of a spin-up wedge to determine an initial head position on disk spin up, such a servo circuit allows one to increase the disk's storage capacity by reducing the number of, or altogether eliminating, spin-up servo wedges from the disk.
    Type: Grant
    Filed: November 5, 2001
    Date of Patent: June 3, 2008
    Assignee: STMicroelectronics, Inc.
    Inventor: Hakan Ozdemir
  • Patent number: 7369351
    Abstract: Embodiments of the invention reduce the error rate of a read error that is caused by a spacing interval between a write head and a read head, which are formed on a slider. In one embodiment, a write head writes user data, which is placed at a position, on a magnetic disk when a read head is placed at a target position in accordance with a head spacing interval and yaw angle. DHO adjustment data is written at a second position, which is obtained by subjecting the read head to DHO correction in order to read the user data written at the target position. When the user data is to be read, a processor reads the DHO adjustment data, changes the read head position to the first position, and controls the operation of a magnetic disk drive to read the user data.
    Type: Grant
    Filed: November 22, 2005
    Date of Patent: May 6, 2008
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Kazuyuki Date, Masayoshi Shimokoshi
  • Patent number: 7365933
    Abstract: Embodiments of the invention provide optimum servo patterns for perpendicular magnetic recording method. In one embodiment, a burst field of servo patterns is composed of burst-signal parts in each of which a constant frequency occurs successively and zero-signal parts each of which has been demagnetized to a state of zero-magnetization, and the total magnetization of the burst field is made approximately 0. The zero signal portions are formed by shutting off a write current at a time during an operation to record servo patterns on a disk initialized to a state of zero-magnetization. The total magnetization of all servo patterns is made approximately 0 by encoding an address mark field and a track code field of servo patterns by a phase shift method.
    Type: Grant
    Filed: January 12, 2006
    Date of Patent: April 29, 2008
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Takehiko Hamaguchi, Hideaki Maeda, Kazuaki Usui, Kazuhisa Shishida, Takashi Konishi
  • Publication number: 20080094746
    Abstract: A disk drive correctly recognizes newly written data when a plurality of readable data exist on the same sector of the same track, by comparing AGC values of each of the readable data, comparing error rates generated by Viterbi decoding, or both. An offset value determining means determines whether an offset value when the data is read has exceeded a predetermined value when the data is read. An offset control means controls the head, on the basis of the determination result of the offset value determining means, to conduct the offset operation on the opposite side of the track when the data is read the first time, and a selecting means selects the new data recorded in the sector by comparing the results obtained for both sets of data.
    Type: Application
    Filed: May 10, 2007
    Publication date: April 24, 2008
    Applicant: Fujitsu Limited
    Inventor: Osamu Yoshida
  • Patent number: 7355810
    Abstract: According to one embodiment, a disk drive using a disk medium in which servo information is embedding-recorded by a DTR method has a structure wherein a phase-difference servo burst pattern included in the servo information embedded in servo regions on the disk medium has a single inclined direction being the same as a direction of an inline angle of a head.
    Type: Grant
    Filed: August 28, 2006
    Date of Patent: April 8, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Makoto Asakura
  • Publication number: 20080080082
    Abstract: Timing recovery and synchronization for data communication is utilized. A pilot sequence of signals can be selected to improve recovery of a phase offset and a frequency offset in a communication system. Sampling instances can further be adjusted based on pilot sequences within a user data portion.
    Type: Application
    Filed: September 28, 2006
    Publication date: April 3, 2008
    Applicant: Seagate Technology LLC
    Inventors: Mehmet Fatih Erden, Erozan Mehmet Kurtas, Mark Edward Re
  • Patent number: 7352526
    Abstract: A storage device has a separate type magnetic head and a discrete type magnetic recording medium on which recording tracks and recording disabled areas are alternately formed. An accurate offset of the magnetic head with respect to the magnetic recording medium is measured even if the widths of the elements of the separate type head differ. While changing the write position and read position of a magnetic recording head, a write element writes measurement data to a magnetic recording medium, a read element reads the written measurement data, and the signal quality is measured and the write offset value and the read offset value are calculated from the inflexion points of a contour line on the two-dimensional map on the measured signal quality. Even if the widths of the write element and the read element differ depending on the individual magnetic recording head, an offset with respect to the separated recording tracks can be accurately measured.
    Type: Grant
    Filed: June 19, 2006
    Date of Patent: April 1, 2008
    Assignee: Fujitsu Limited
    Inventor: Kazuhiko Takaishi
  • Publication number: 20080074778
    Abstract: Various systems and methods for providing head location feedback are disclosed herein. For example, one system includes an interface circuit that is operable to receive an information stream retrieved from a magnetic storage medium. The magnetic storage medium includes one or more tracks that each include a plurality of sectors. The sectors include burst information that can be utilized to aid in positioning a read/write head assembly over a magnetic storage medium. The systems further include a multiple sector error detection circuit. The multiple sector error correction circuit is operable to phase align samples of a burst obtained from one sector with samples of a burst obtained from another sector. An amplitude of each of the bursts is determined, and the determined amplitudes are combined. The combined amplitudes correspond to a position error of the read/write head assembly relative to the magnetic storage medium.
    Type: Application
    Filed: September 22, 2006
    Publication date: March 27, 2008
    Inventor: Viswanath Annampedu
  • Patent number: 7349167
    Abstract: An apparatus comprises a data storage medium having a plurality of servo sectors and a plurality of data sectors, wherein each of the servo sectors includes a phase locked loop field and a track identification field, a controller for controlling the position of a recording head with respect to the data storage medium, and a servo demodulator for recovering timing information from both the phase locked loop field and the track identification field, and for producing a timing estimate. The method performed by the apparatus is also included.
    Type: Grant
    Filed: July 27, 2005
    Date of Patent: March 25, 2008
    Assignee: Seagate Technology LLC
    Inventors: Mehmet Fatih Erden, Richard Lyle Keizer, Timothy Francis Ellis, Alexei Hiram Sacks
  • Publication number: 20080062553
    Abstract: In the case of a magnetic head tracing a record track from the left to right, a positional demodulation signal obtained by passing a first servo sector existing in the record track is minutely corrected by a positional correction signal converted from a phase shift amount which is obtained by sequentially passing at least plurally placed correction areas, thereby becoming a positional signal, followed by obtaining a positional modulation signal in the same manner at a second servo sector existing in the record track subsequently traced, and further minutely corrected by a positional correction signal obtained by passing similar plural correction areas arrayed at discretionary intervals starting from the second servo area. Such minute correction operations are performed for one circumference of a track, which is continued for carrying out an accurate positioning trace to a target track.
    Type: Application
    Filed: January 12, 2007
    Publication date: March 13, 2008
    Inventor: Takayuki Kawabe
  • Patent number: 7342737
    Abstract: Methods of filtering a position error signal (PES) indicative of a position of a transducer of a disk drive include obtaining sample position data for the transducer, eliminating selected data of the sample position data to provide a subset of the sample position data, obtaining a plurality of sets of preliminary filter coefficients based on the subset of the sample position data, obtaining a final set of filter coefficients from the plurality of sets of preliminary filter coefficients, and filtering a position error signal using the final set of filter coefficients. Corresponding disk drives are also disclosed.
    Type: Grant
    Filed: October 17, 2006
    Date of Patent: March 11, 2008
    Assignee: Seagate Technology LLC
    Inventors: Jeffrey V. DeRosa, Orhan Beker
  • Patent number: 7342734
    Abstract: A disk drive includes a rotatable data storage disk, a transducer, an actuator, and a servo burst demodulator. The rotatable data storage disk includes a plurality of servo burst patterns thereon. The plurality of servo burst patterns are substantially radially aligned to each other, and radially adjacent ones of the servo burst patterns are configured to generate contributions to a read signal that are substantially orthogonal to each other. The transducer is configured to read the servo burst patterns on the disk to generate the read signal. The actuator is configured to position the transducer relative to the disk. The servo burst demodulator is configured to identify a separate contribution to the read signal from the radially adjacent servo burst patterns. The servo burst demodulator may be configured to generate transducer position information based on the identified separate contribution to the read signal from the radially adjacent servo burst patterns.
    Type: Grant
    Filed: December 14, 2004
    Date of Patent: March 11, 2008
    Assignee: Maxtor Corporation
    Inventors: Ara Patapoutian, Michael Leis, Bruce Buch
  • Patent number: 7339761
    Abstract: A method is disclosed for identifying wedge time shift zones on a magnetic disk of a disk drive. The disk drive further includes a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, and a head that is actuated over the disk. During operation, the control systems causes a seek of the head across the disk and measures wedge-to-wedge times between servo wedges. The control system then calculates a wedge-to-wedge time shift value using the wedge-to-wedge times and determines whether the wedge-to-wedge time shift time value exceeds a predetermined threshold. If the wedge-to-wedge time shift value exceeds the predetermined threshold, then the control system identifies a wedge time shift zone, and stores information for compensating for the identified wedge time shift zone during disk operations.
    Type: Grant
    Filed: April 18, 2006
    Date of Patent: March 4, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Kuang-Yang Tu, John Yin Kwong Li
  • Patent number: 7336438
    Abstract: The present invention relates to a write control method of a hard disk drive, a hard disk drive adapting the method, and a recording medium storing a program for executing the method. The write control method of a hard disk drive having a disk where servo bursts are written radially comprises: generating a primary position error signals (PESs) with respect to a target offtrack based on a difference between servo burst signals read from two adjacent servo bursts; generating a secondary PES with respect to the target offtrack based on a sum of the primary PESs or a difference there between; determining whether both the primary PESs and the secondary PES are within a predetermined write bump limit; and performing a write operation at the target offtrack if both the primary PESs and the secondary PES are within the predetermined write bump limit, otherwise prohibiting the write operation.
    Type: Grant
    Filed: June 15, 2006
    Date of Patent: February 26, 2008
    Assignee: Samsung Electronics Co., Ltd.
    Inventors: Cheol-hoon Park, Sang-hoon Chu
  • Patent number: 7333289
    Abstract: A magnetic recording and reproducing apparatus and a method of controlling the same, capable of increasing the output of a position control signal and performing a precise positioning control of a magnetic head. The magnetic recording and reproducing apparatus has: a magnetic recording medium on which a positional information is recorded in the form of burst signal groups each consisting of either one of a single concave portion and a single convex portion of a predetermined concavo-convex pattern formed of a magnetic layer; a gate circuit; and an integrator for calculating a area integral of a reproduced signal corresponding to each of the burst signal groups.
    Type: Grant
    Filed: March 17, 2006
    Date of Patent: February 19, 2008
    Assignee: TDK Corporation
    Inventors: Akimasa Kaizu, Yoshikazu Soeno, Makoto Moriya
  • Patent number: 7333290
    Abstract: Disclosed is a magnetic disk having servo sectors for defining data tracks. Each servo sector includes a preamble field and a null servo burst field. The preamble field is for synchronizing a phase-locked loop oscillator and defines a reference phase angle. The null servo burst field includes first and second servo bursts that are radially adjacent and have opposed phase angles such that a read along a null path that is equally between the first and second servo bursts generates a read signal of substantially zero amplitude, and a read along a path that is offset from the null path generates a read signal having an amplitude indicating a distance between the offset path and the null path, and having a phase indicating an offset direction. Further, the phase angle of the first and second servo bursts are substantially different from the reference phase angle.
    Type: Grant
    Filed: August 3, 2006
    Date of Patent: February 19, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventor: Hanan Kupferman
  • Patent number: 7319568
    Abstract: A magnetic recording media has a magnetic layer formed on a substrate and includes data regions including a magnetic pattern constituting a recoding track and servo regions including magnetic patterns used as address bits, the data regions and the servo regions being contained in a plane of the magnetic layer. In a case where two magnetic patterns used as address bits on the servo regions corresponding to two adjacent recording tracks are arranged in such a manner that one corner of one of the magnetic patterns is closest to one corner of the other, the corners of the two magnetic patterns are substantially joined together.
    Type: Grant
    Filed: July 15, 2005
    Date of Patent: January 15, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Takeshi Okino, Akira Kikitsu, Yoichiro Tanaka, Yoshiyuki Kamata
  • Patent number: RE40545
    Abstract: A servo control apparatus and method controls systems at least partially on the basis of an observable variable that has an absolute value functional relationship with the controlled variable and does not change sign for positive and negative variations from a nominal value. When applied to the positional control of an object, the control system observes a value of a position error signal and maps that signal to two different potentially correct displacement values. Two estimators within the control system are initiated, one using the positive displacement and the other using the negative displacement, and the two estimators each predict the future position of the object and the corresponding position error signal for each estimated position. A new position error signal is detected and compared to the two estimated position error signals.
    Type: Grant
    Filed: April 8, 2005
    Date of Patent: October 21, 2008
    Assignee: Purchased Patent Management LLC
    Inventors: Petros A. Ioannou, Elias B. Kosmatopoulos, Alvin M. Despain