Checking Record Characteristics Or Modifying Recording Signal For Characteristic Compensation Patents (Class 360/25)
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Patent number: 8031420Abstract: In a hard-disc drive read channel, frequency-based measures are generated at two different data frequencies (e.g., 2T and DC) by applying a transform, such as a discrete Fourier transform (DFT), to signal values, such as ADC or equalizer output values, corresponding to, e.g., a 2T data pattern stored on the hard disc. The frequency-based measures are used to detect defect regions on the hard disc and/or to classify defect regions as being due to either thermal asperity (TA) or drop-out media defect (MD).Type: GrantFiled: February 18, 2010Date of Patent: October 4, 2011Assignee: LSI CorporationInventors: George Mathew, Yang Han, Shaohua Yang, Zongwang Li, Yuan Xing Lee
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Patent number: 8000054Abstract: A control device includes an acquisition section which acquires a reading signal from a head under plural heat amounts, an computation section which computes plural kinds of characteristic values representing characteristics of the reading signal for each of the plural generated heat amounts by using at least one kind of algorithm, a contact determination section which determines whether or not the head contacts the storage medium for each of the two or more kinds of characteristic values based on a change of the characteristic values for the generated heat amount, and an association determination section which determines an association of a distance between the head and the storage medium with the generated heat amount when determined that the head contacts the storage medium for any of the characteristic values as the generated heat amount when the head contacts the storage medium so that the is considered to be zero.Type: GrantFiled: July 21, 2009Date of Patent: August 16, 2011Assignee: Toshiba Storage Device CorporationInventor: Yukio Urata
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Patent number: 7986479Abstract: A corrector circuit for correcting second harmonic distortions is provided. The corrector circuit includes a transconductance circuit having an input transconductance with a transresistance load for receiving a distorted voltage signal having a second harmonic component. The transconductance circuit is adapted to generate a corrected voltage signal having the second harmonic component that is reduced from the distorted voltage signal as a function of the input transconductance. The corrector circuit further includes biasing means for providing a biasing current to the transconductance circuit (with the input transconductance that depends on the biasing current). The biasing means includes means for providing a fixed component of the biasing current, means for providing a variable component of the biasing current (being a function of the distorted voltage signal according to a proportionality coefficient) and means for programming the proportionality coefficient.Type: GrantFiled: February 26, 2007Date of Patent: July 26, 2011Assignee: STMicroelectronics, S.r.l.Inventors: Giacomino Bollati, Marco Bongiorni
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Patent number: 7982987Abstract: A method and apparatus for detecting predetermined surface characteristics in head gimbal assemblies to improve hard disk drive reliability. The predetermined surface characteristics include head slider protrusions such as scratches or contamination that can cause damage to the head or disk in hard drives. By detecting these protrusions, those drives with an increased chance of failure can be removed from a test group, thereby increasing the quality and reliability of the remaining disk drives. The invention provides a method of detecting these protrusions that is a more practical option than using a scanning electron microscope (SEM) to inspect each head slider.Type: GrantFiled: December 8, 2008Date of Patent: July 19, 2011Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Youping Deng, Randall G. Simmons, Wing T. Tang, Huiping Yang
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Publication number: 20110141598Abstract: There is provided a detect inspection method and apparatus capable of performing a quick process of determining whether defects on a disk form an annular scratch defect or an island defect, by detecting an annular scratch defect in sum track areas with a deviation exceeding the standard deviation of an amount of defects detected in radius, in the histogram data containing the number of defects in radius, or by detecting an island defect in sum angle areas with a deviation exceeding the standard deviation of an amount of defects detected in angle, in the histogram data containing the number of defects in angle. Thus, the defect detection process can be performed step by step, by separating the annular scratch defect or the island defect from the other detects. As a result, a process load on the data processor can be reduced even if the number of detected defects increases.Type: ApplicationFiled: December 14, 2010Publication date: June 16, 2011Inventor: Hideki MOCHIZUKI
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Publication number: 20110141597Abstract: A tape library system includes a plurality of cartridge cells for accommodating a plurality of tape cartridges respectively, a tape drive for writing and reading data to and from the tape cartridge inserted therein, a diagnosis drive for diagnosing the tape cartridge inserted therein, an cartridge carriage mechanism for inserting and ejecting the tape cartridge into and from the tape drive and the diagnosis drive, and a diagnosis controller for controlling the cartridge carriage mechanism to load the tape cartridge into the diagnosis drive and for controlling the diagnosis drive to diagnose the tape cartridge inserted therein.Type: ApplicationFiled: June 17, 2010Publication date: June 16, 2011Applicant: FUJITSU LIMITEDInventors: Takaaki YAMATO, Shigeru Tsukada, Nobuyuki Hirashima
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Patent number: 7953911Abstract: A method and apparatus to read information from an information storage medium using a read channel, where that read channel includes a data cache. The invention generates an analog waveform comprising the information, and provides that analog waveform to a read channel, and generates a digital signal from that analog waveform using one or more first operating parameters. The method error corrects that digital signal at an actual error correction rate, and determines if the actual error correction rate is greater than an error correction rate threshold. If the actual error correction rate exceeds the error correction rate threshold, then the method captures the digital signal, stores that captured data in a data cache, reads that digital signal from the cache, generates one or more second operating parameters, and provides those one or more second operating parameters to the read channel.Type: GrantFiled: August 24, 2010Date of Patent: May 31, 2011Assignee: International Business Machines CorporationInventors: James J. Howarth, Robert A. Hutchins
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Patent number: 7933084Abstract: A signal reconstruction technique is used to correct for wow and flutter in analog audio recordings. Elements of the recording are used to generate a signal for correcting the output. Involves locating modulated entities such as bias signal (e.g. frequency-modulated, amplitude-modulated, or phase-modulated entities) in the recording, extracting them, and utilizing them as a carrier to synchronize to a master clock, using the irregularity of the anomaly to indicate the speed and pitch information to be corrected. A carrier frequency is determined and applied to a digitized form of the recording. This may be performed even in the absence of a prescribed reference code or tone, such as a pilot tone laid down purposefully at the moment of recording. In the case of signals presumed to have an error in the carrier, a corresponding signal is buffered, and in the case of a presumed error, a last known signal is used for the duration of the error.Type: GrantFiled: October 6, 2003Date of Patent: April 26, 2011Inventors: James R. Howarth, Patrick J. Wolfe, Darryl Curley, Timothy Rector
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Patent number: 7924518Abstract: Various embodiments of the present invention provide systems and methods for write pre-compensation. For example, various embodiments of the present invention provide methods for modifying magnetic information transfer. The methods include retrieving magnetically represented data from a storage medium, and converting the magnetically represented data to a series of data samples. A preceding pattern and a transition status is identified in the series of data samples, and an equalized channel response is computed based on an estimated NLTS value. An error value is computed that corresponds to a difference between the estimated NLTS value and an actual NLTS value, and a pre-compensation value is computed based at least in part on the error value.Type: GrantFiled: August 27, 2008Date of Patent: April 12, 2011Assignee: LSI CorporationInventors: George Mathew, Yuan Xing Lee, Hongwei Song
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Patent number: 7889446Abstract: A read channel includes a variable gain amplifier, a low-pass filter, an AGC, an analog-to-digital converter, a frequency synthesizer, a filter, a soft-output detector, an LDPC decoding unit, a synchronizing signal detector, a run-length limited decoding unit, a descrambler, and a first baseline wander corrector. The first baseline wander corrector corrects a baseline variation by a feedforward control.Type: GrantFiled: March 4, 2008Date of Patent: February 15, 2011Assignee: Rohm Co., Ltd.Inventors: Atsushi Esumi, Kai Li, Hidemichi Mizuno
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Patent number: 7885031Abstract: Systems and techniques relating to interpreting signals on a channel having an asymmetrical signal amplitude response. A signal processor, such as a read channel transceiver device usable in a magnetic recording system, includes an asymmetry correction circuit configured to receive an analog signal and to compensate for asymmetry in the received analog signal, a signal equalizer configured to receive an input signal responsive to an output of the asymmetry correction circuit and to generate an equalized signal, a discrete time sequence detector operable to examine the equalized signal, and a control circuit that provides a coefficient adjustment to the asymmetry correction circuit to affect the asymmetry compensation based on an estimate of non-linearity derived from the equalized signal and an output of the discrete time sequence detector. The estimate can be a least mean squared estimate of the non-linearity in the equalized signal.Type: GrantFiled: May 29, 2009Date of Patent: February 8, 2011Assignee: Marvell International Ltd.Inventor: Ke Han
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Patent number: 7880986Abstract: A phase interpolator is provided that, in one implementation, includes an output node, a plurality of phase input circuits, and a plurality of switches corresponding to the plurality of phase input circuits. Each phase input circuit is operable to receive a given phase signal. Each switch is in communication with a given phase input circuit and is operable to couple a given phase signal to the output node.Type: GrantFiled: August 7, 2009Date of Patent: February 1, 2011Assignee: Marvell International Ltd.Inventor: Chi Fung Cheng
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Patent number: 7880987Abstract: Certifying a storage media while servowriting the media by formatting a full compliment of servo data in storage tracks of the media in a minimum number of passes per storage track while simultaneously performing a 100% media certification of the storage tracks during the minimum number of passes per storage track.Type: GrantFiled: January 17, 2008Date of Patent: February 1, 2011Assignee: Seagate Technology LLCInventors: Ken L. Belmont, Dan R. McLeran, Dave Scott Williamson, Mark Christian Roberts, Gabor Szita
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Patent number: 7872821Abstract: Various embodiments of the present invention provide systems and methods for determining changes in fly-height. For example, various embodiments of the present invention provide storage devices that include a storage medium, an offset frequency, a read/write head assembly, and a harmonic fly-height change detection circuit. The storage medium includes a periodic data pattern that repeats at a data frequency. The read/write head assembly disposed in relation to the storage medium such that it senses the periodic data pattern and provides a sensed periodic data pattern. The harmonic fly-height change detection circuit samples the sensed periodic data pattern at an aggregate frequency to yield a first set of samples and a second set of samples. The aggregate frequency is the data frequency adjusted by the offset frequency. The harmonic fly-height change detection circuit calculates a first magnitude of the first set of samples and a second magnitude of the second set of samples.Type: GrantFiled: April 28, 2009Date of Patent: January 18, 2011Assignee: LSI CorporationInventors: Jeffrey P. Grundvig, George Mathew
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Patent number: 7864464Abstract: A system reads data from a magnetic storage media. A read head reads data from the magnetic storage media and produce an analog signal. A variable gain amplifier amplifies the analog signal. An offset adjust module substantially centers the amplified analog signal to a midscale. A Magneto Resistive Asymmetry (MRA) correction module MRA corrects the amplified analog signal. A Continuous Time Filter (CTF) compensation module processes the amplified analog signal. An Analog to Digital Converter (ADC) samples the amplified analog signal based upon a control signal to produce a digital signal. A Disk Lock Clock (DLC) system produces the control signal to the ADC. The control signal is representative of a frequency offset caused by at least one servo wedge rate error. A Finite Impulse Response (FIR) filter module filters the digital signal. A sequence detector processes the digital signal and detects a bit sequence from the digital signal.Type: GrantFiled: December 29, 2009Date of Patent: January 4, 2011Assignee: Broadcom CorporationInventors: William Gene Bliss, Thomas V. Souvignier
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Patent number: 7848042Abstract: Removing magneto-resistive asymmetry (MRA) from a signal is disclosed. Removing MRA includes determining an estimated offset error associated with error due to offset in the signal, determining an estimated signal error associated with error due to offset and MRA in the signal, and removing at least a portion of MRA from the signal based at least in part on the estimated offset error and the estimated signal error.Type: GrantFiled: April 12, 2007Date of Patent: December 7, 2010Assignee: Link—A—Media Devices CorporationInventor: Marcus Marrow
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Patent number: 7848037Abstract: A method for testing a hard disk drive is described. The method includes determining a number of defects associated with a portion of recordable media associated with a hard disk drive. The method further includes comparing the number of determined defects to a threshold number of defects and provided the number of determined defects is greater than the threshold number of defects, determining that the portion of the disk comprises disk defects.Type: GrantFiled: November 19, 2007Date of Patent: December 7, 2010Assignee: Hitachi Global Storage Technologies, Netherlands, B.V.Inventors: Youping Deng, Terry Farren, Jing Zhang
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Patent number: 7821731Abstract: A storage channel, e.g., for a disk drive system, may asynchronously sample and buffer an entire sector, and then process the buffered sector to recover timing information. The storage channel may operate in an open-loop and utilize an exhaustive search to determine timing parameters. Alternatively, the storage channel may operative in a closed-loop, processing the sector once, and feeding back information obtained during decoding to the timing loop.Type: GrantFiled: October 31, 2007Date of Patent: October 26, 2010Assignee: Marvell International Ltd.Inventors: Pantas Sutardja, Ke Han, Zining Wu
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Patent number: 7817363Abstract: In one embodiment, defects are detected on the face of a hard-disk drive platter. A preamble, a sync mark, user or pseudorandom data, and a data pad are written to every sector on a track of the platter. Inter-sector gaps that separate consecutive sectors are overwritten with a fixed data pattern such that consecutive sectors are in phase lock with one another. After the track has been written, the track is read back and analyzed. Consecutive sectors are analyzed continuously without stopping. The preambles, sync marks, data pads, and overwritten inter-sector gaps are analyzed using suitable flaw-scan techniques. The user or pseudorandom data is analyzed using both data-integrity checks and suitable flaw-scan techniques. This process is repeated for all tracks on the disk, and defect detection is completed when all tracks have been analyzed.Type: GrantFiled: November 17, 2008Date of Patent: October 19, 2010Assignee: Agere Systems Inc.Inventors: Keenan T. O'Brien, Richard Rauschmayer
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Patent number: 7817362Abstract: An inspection apparatus and method are disclosed for inspecting a magnetic disk or a magnetic head. A first reference signal generating source generates reference signals of a controllable oscillating frequency, and a signal switching means selects either a reference signal or test data reproduced by the magnetic head. Factors such as offsets and gain differentials among signal distribution paths, phase shifts of sampling clocks supplied to a plurality of AID converters, and frequency-dependence of the transfer function and phase response of signal paths are identified so that errors due to these factors can be detected. Based on the detected values of these factors and errors, reference signals are utilized to compensate test data errors.Type: GrantFiled: January 21, 2003Date of Patent: October 19, 2010Inventors: Masayoshi Takahashi, Ritsuro Orihashi, Wen Li, Shinji Homma
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Patent number: 7817368Abstract: Systems and techniques relating to interpreting signals on a channel having an asymmetrical signal amplitude response can include generating multiple asymmetry matrices that model asymmetry in a received analog signal, including an effect of asymmetry spreading in a read channel; comparing the multiple asymmetry matrices; and selecting indicators of asymmetry from the matrices based on the comparing. Systems and techniques can include saving in memory an indication of the selected indicators of asymmetry.Type: GrantFiled: March 16, 2009Date of Patent: October 19, 2010Assignee: Marvell International Ltd.Inventor: Ke Han
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Patent number: 7800858Abstract: A method and system for providing a disk drive is described. The disk drive includes media such as one or more disks, a slider, and a head residing on the slider. The head has an air-bearing surface (ABS), a portion of which contacts the media during touchdown. The head further includes a plurality of touchdown sensors. A first touchdown sensor is proximate to the ABS, while a second touchdown sensor is distal from the ABS. The touchdown sensors are capable of detecting a temperature change of 0.1 degree Celsius or, in some embodiments, smaller.Type: GrantFiled: May 4, 2009Date of Patent: September 21, 2010Assignee: Western Digital (Fremont), LLCInventors: Sateeshchandra S. Bajikar, David E. Fowler
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Patent number: 7796356Abstract: A method and system for providing a disk drive is described. The disk drive includes media such as one or more disks, a slider and a head residing on the slider. The head has an air-bearing surface (ABS) and includes a touchdown sensor proximate to the ABS. The touchdown sensor is capable of detecting a temperature change of 0.1 degree Celsius or, in some embodiments, smaller. The disk drive also includes touchdown sensor control circuitry coupled with the touchdown sensor. The touchdown sensor control circuitry drives a current through the touchdown sensor and converts a signal from the touchdown sensor into an indication of whether touchdown has occurred.Type: GrantFiled: May 4, 2009Date of Patent: September 14, 2010Assignee: Western Digital (Fremont), LLCInventors: David E. Fowler, Sateeshchandra S. Bajikar
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Patent number: 7793020Abstract: A method and apparatus to read information from an information storage medium using a read channel, where that read channel includes a data cache. The invention generates an analog waveform comprising the information, and provides that analog waveform to a read channel, and generates a digital signal from that analog waveform using one or more first operating parameters. The method error corrects that digital signal at an actual error correction rate, and determines if the actual error correction rate is greater than an error correction rate threshold. If the actual error correction rate exceeds the error correction rate threshold, then the method captures the digital signal, stores that captured data in a data cache, reads that digital signal from the cache, generates one or more second operating parameters, and provides those one or more second operating parameters to the read channel.Type: GrantFiled: November 27, 2002Date of Patent: September 7, 2010Assignee: International Business Machines CorporationInventors: James J. Howarth, Robert A. Hutchins
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Patent number: 7773324Abstract: A phase-acquisition (PA) loop for a read channel comprises an accumulator, a comparator, and a filter. The accumulator holds an acquired phase-correction value corresponding to a difference between a phase of a sample clock and a phase of data carried by a read signal, and provides the acquired phase-correction value to a circuit that modifies the read signal to compensate for the phase difference. The comparator receives a reference phase-correction value that also corresponds to the difference between the phases of the sample clock and the data, and generates an error signal that is related to a difference between the reference and acquired phase-correction values. And the filter causes the acquired phase-correction value to have a predetermined relationship to the reference phase-correction value.Type: GrantFiled: April 10, 2006Date of Patent: August 10, 2010Assignee: STMicroelectronics, Inc.Inventor: Hakan Ozdemir
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Patent number: 7768732Abstract: A gain controller for a gain loop of a read channel includes a comparator circuit, an accumulator circuit, and a function circuit. The comparator circuit determines an error between an actual sample of a read signal and a corresponding ideal sample of the read signal, and the accumulator circuit holds a gain-correction value and adjusts the gain-correction value in response to the error. The function circuit generates a gain-correction signal by performing a predetermined mathematical operation involving the gain-correction value, and provides the gain-correction signal to a variable-gain amplifier that is operable to amplify actual samples of the read signal. Because such a gain controller allows one to locate the variable-gain amplifier (VGA) after the analog-to-digital converter (ADC) in a read channel, the gain controller may significantly reduce the latency of the gain-acquisition (GA) loop or the gain-tracking (GT) loop of the read channel.Type: GrantFiled: April 10, 2006Date of Patent: August 3, 2010Assignee: STMicroelectronics, Inc.Inventor: Hakan Ozdemir
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Patent number: 7761244Abstract: One embodiment of the present invention provides a system that mitigates the effects of multiple vibration sources on a set of hard disk drives (HDDs) within a computer system. During operation, the system identifies a target HDD in the set of HDDs, wherein the performance of the target HDD is affected by mechanical vibrations. The system also identifies one or more primary vibration sources from the multiple vibration sources that affect the performance of the target HDD. Next, for each of the primary vibration sources, the system measures a first time-domain signal associated with the operation of the primary vibration source using a first vibration transducer associated with the primary vibration source. The system also measures a second time-domain signal associated with the target HDD using a second vibration transducer associated with the target HDD.Type: GrantFiled: September 7, 2007Date of Patent: July 20, 2010Assignee: Oracle America, Inc.Inventors: Kenny C. Gross, Aleksey M. Urmanov, Kalyanaraman Vaidyanathan
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Patent number: 7760457Abstract: A channel senses head-to-disc contact vibrations in a vibrational noise spectrum produced in a mass storage device. The channel includes a suspension system with a suspension modal resonance. The channel includes a vibration sensor that senses head-to-disc contact vibrations through the suspension system. The vibration sensor has a sensor modal resonance that overlaps the suspension modal resonance.Type: GrantFiled: March 4, 2009Date of Patent: July 20, 2010Assignee: Seagate Technology LLCInventors: Neal Frank Gunderson, Jason Wayne Riddering, John Stuart Wright
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Patent number: 7738206Abstract: A method and apparatus for providing an early warning of thermal decay in magnetic storage media are provided. In accordance with an embodiment of the present invention, a test pattern that is particularly susceptible to thermal decay is written to a disk. The test pattern is then read, and the amplitude of the signal produced by the test pattern is stored. When testing for thermal decay is desired, the test pattern is again read, and the amplitude of the signal produced in the channel is compared to the stored amplitude. If the later amplitude is less than the stored amplitude by at least a predetermined amount, a thermal decay warning signal is generated. In accordance with another embodiment of the present invention, a test pattern is written to a portion of a disk that has been identified as being particularly susceptible to thermal decay. The amplitude produced by the test pattern is then stored so that it can later be compared to an observed amplitude when testing for thermal decay.Type: GrantFiled: August 3, 2001Date of Patent: June 15, 2010Assignee: Seagate Technology LLCInventors: G. Herbert Lin, Davidc Guarisco, Xiaokun Chew
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Patent number: 7667916Abstract: Apparatus, systems, and methods implementing techniques for converting a signal. In an apparatus form, an input circuit receives a differential input signal and produces a single-ended intermediate signal. An amplifier circuit receives the intermediate signal and produces an amplified signal, and a feedback path couples the amplified signal to the intermediate signal. An inverter circuit receives the amplified signal and produces an output signal.Type: GrantFiled: April 26, 2004Date of Patent: February 23, 2010Assignee: Marvell International Ltd.Inventor: Farbod Aram
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Patent number: 7646556Abstract: A flaw scan system for detecting a location of first and second types of location specific anomalies on a storage disk of a hard disk drive comprising a write system, a read system, and first and second anomaly location systems. The write system writes a first set of bits to the storage disk in first and second data patterns. The read system reads the first set of bits from the storage disk. The first anomaly location system determines locations of the first type of location specific anomaly based on the first data pattern. The second anomaly location system determines locations of the second type of location specific anomaly based on the second data pattern.Type: GrantFiled: July 10, 2006Date of Patent: January 12, 2010Assignee: Seagate Technology LLCInventors: K. Rickmer E. Kose, Bin Liu
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Patent number: 7643233Abstract: A system reads data from a magnetic storage media. A read head reads data from the magnetic storage media and produce an analog signal. A variable gain amplifier amplifies the analog signal. An offset adjust module substantially centers the amplified analog signal to a midscale. A Magneto Resistive Asymmetry (MRA) collection module MRA corrects the amplified analog signal. A Continuous Time Filter (CTF) compensation module processes the amplified analog signal. An Analog to Digital Converter (ADC) samples the amplified analog signal based upon a control signal to produce a digital signal. A Disk Lock Clock (DLC) system produces the control signal to the ADC. The control signal is representative of a frequency offset caused by at least one servo wedge rate error. A Finite Impulse Response (FIR) filter module filters the digital signal. A sequence detector processes the digital signal and detects a bit sequence from the digital signal.Type: GrantFiled: April 27, 2008Date of Patent: January 5, 2010Assignee: Broadcom CorporationInventors: William Gene Bliss, Thomas V. Souvignier
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Publication number: 20090316287Abstract: A tape drive system for a tape cartridge including a tape and wireless identification tag may read information from the wireless identification tag and write the information to the tape. The tape drive system may toggle a bit stored on the wireless identification tag to indicate that the information has been written to the tape. The information may include tape initialization information.Type: ApplicationFiled: June 19, 2008Publication date: December 24, 2009Applicant: SUN MICROSYSTEMS, INC.Inventors: Steven Michael Kientz, Matthew P. Wojciechowski
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Patent number: 7633694Abstract: The present invention provides a method and apparatus for quantifying stress and damage in magnetic heads. A change in a performance parameter of a magnetic recording head is characterized. The head is stressed by loading it onto and flying it over a rough zone of the recording medium. A post-stress read-back signal is read from the bit pattern written on the recording medium using the head subsequent to the stressing of the head. A performance parameter of the head is calculated using the post-stress read-back signal. The performance parameter of the head calculated using the post-stress read-back signal is compared to a performance parameter of the head calculated using a pre-stress read-back signal to characterize a change in performance of the head resulting from the stressing of the head.Type: GrantFiled: March 31, 2006Date of Patent: December 15, 2009Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Michael Alex, Li Tang
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Patent number: 7630154Abstract: A method an apparatus for testing the surface of hard disk platters having vertically oriented magnetic domains is disclosed. According to the method of the present invention, all of the magnetic domains on the surface of the disk to be tested are oriented in the same direction, so that the magnetic field intensity adjacent to the surface is ideally uniform. The surface is then scanned using a read head to identify perturbations in the magnetic field intensity which correlate to surface defects.Type: GrantFiled: April 4, 2006Date of Patent: December 8, 2009Assignee: MRA Tek, LLCInventors: Stephen Frank Meier, David H. Ferry
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Patent number: 7626777Abstract: A method and apparatus for detecting signal peaks caused by a thermal asperity event in a magnetic recording media to reduce data reading errors introduced by the thermal asperity event. A common mode voltage is determined for differential signals representing data bits read from the magnetic recording media and a threshold voltage produced responsive to the common mode voltage. A comparator determines if either of the differential signals exceeds the threshold voltage, thereby indicating the occurrence of a thermal asperity event.Type: GrantFiled: September 23, 2005Date of Patent: December 1, 2009Assignee: Agere Systems Inc.Inventors: Arvind R. Aemireddy, Ronen Malka, Jeffrey A. Gleason, Scott M. O'Brien
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Patent number: 7623309Abstract: Plural information transfer elements transfer signals from plural magnetic tape tracks of plural tapes. Each element and track has a different non-linear transfer function. A processor (1) determines appropriate compensation for the signal one of the transfer elements derives, (2) accesses stored information for compensation characteristics of each of the data transfer elements, and (3) references the accessed information with the compensation determined for the one element to establish an appropriate compensation for the other elements.Type: GrantFiled: April 28, 2004Date of Patent: November 24, 2009Assignee: Hewlett-Packard Development Company, L.P.Inventor: Allan Hodkinson
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Publication number: 20090244750Abstract: A magnetic-recording-medium testing apparatus includes a frequency-characteristic analyzing unit that analyzes a frequency characteristic of a reproduced signal in an area of a magnetic material where a continuous frequency signal is written, in a magnetic recording medium that records a signal according to a magnetization direction of the magnetic material, a signal-amplitude comparing unit that compares signal amplitudes of a fundamental wave and a higher harmonic wave with each other based on the frequency characteristic analyzed by the frequency-characteristic analyzing unit, to estimate a cross sectional shape pattern of the magnetic recording medium, and a performance-quality determining unit that determines performance quality of the magnetic recording medium based on the cross sectional shape pattern of the magnetic recording medium estimated by the signal-amplitude comparing unit.Type: ApplicationFiled: December 9, 2008Publication date: October 1, 2009Applicant: FUJITSU LIMITEDInventor: Motomichi Shibano
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Patent number: 7595948Abstract: A perpendicular recording system includes a summing module that has a first input that receives a read signal. A DC correction module selectively generates a DC correction signal to reduce DC offset in the read signal. The DC correction signal is output to a second input of the summing module. A detecting module compares an output of the summing module to a predetermined threshold and selectively detects Thermal Asperity (TA).Type: GrantFiled: April 6, 2004Date of Patent: September 29, 2009Assignee: Marvell International Ltd.Inventor: Mats Oberg
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Patent number: 7583456Abstract: In a perpendicular magnetic recording system, the data that is being written by the write channel is fed back into the read channel. The read channel processes the data and decides if the written sequence is likely to have very poor DC characteristics. If that is the case, the write channel changes a scrambler seed and rewrites the data using the new scrambler seed. The data may also be inspected for patterns that might cause large baseline wander before being written to disk, i.e., in the write channel. A data sequence may be repeatedly scrambled and encoded until an acceptable level of estimated DC-wander has been achieved. The data sequence may then be written to disk.Type: GrantFiled: January 28, 2008Date of Patent: September 1, 2009Assignee: Marvell International Ltd.Inventors: Mats Oberg, Pantas Sutardja
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Patent number: 7583459Abstract: A phase interpolator is provided that, in one implementation, includes an output node, a plurality of phase input circuits, and a plurality of switches corresponding to the plurality of phase input circuits. Each phase input circuit is operable to receive a given phase signal. Each switch is in communication with a given phase input circuit and is operable to couple a given phase signal to the output node.Type: GrantFiled: November 18, 2004Date of Patent: September 1, 2009Assignee: Marvell International Ltd.Inventor: Chi Fung Cheng
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Publication number: 20090168212Abstract: Methods and apparatus for the calibration and use of test glide head gimbal assemblies are disclosed. Calibration is performed by pulse laser adjustment of the flexure mounted to the glide head, while the head is flying above a media test disk having asperities of known dimensions. The calibration process normalizes the fly heights of glide heads used to measure defects on both upper and lower surfaces of disk drive media, allowing upper and lower surfaces to be scanned simultaneously.Type: ApplicationFiled: December 26, 2007Publication date: July 2, 2009Inventors: Karl Arthur Flechsig, Iraj Kavosh, Gurinder Pal Singh, Tim Strand
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Patent number: 7548389Abstract: Systems and techniques relating to interpreting signals on a channel having an asymmetrical signal amplitude response. A signal processor, such as a read channel transceiver device usable in a magnetic recording system, includes an asymmetry correction circuit configured to receive an analog signal and to compensate for asymmetry in the received analog signal, a signal equalizer configured to receive an input signal responsive to an output of the asymmetry correction circuit and to generate an equalized signal, a discrete time sequence detector operable to examine the equalized signal, and a control circuit that provides a coefficient adjustment to the asymmetry correction circuit to affect the asymmetry compensation based on an estimate of non-linearity derived from the equalized signal and an output of the discrete time sequence detector. The estimate can be a least mean squared estimate of the non-linearity in the equalized signal.Type: GrantFiled: October 8, 2007Date of Patent: June 16, 2009Assignee: Marvell International Ltd.Inventor: Ke Han
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Patent number: 7545592Abstract: A flying height of a slider of a head assembly is measured by rotating a disk having at least one protrusion protruding higher than a minimum flying height of the head assembly subject to measurement, and cutting an upper end portion of the protrusion with the slider that is floating with respect to the disk. The cut protrusion is measured to determine the flying height of the slider of the head assembly.Type: GrantFiled: December 16, 2003Date of Patent: June 9, 2009Assignee: Samsung Electronics Co., Ltd.Inventor: Sang-hyub Lee
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Patent number: 7518813Abstract: Methods and structures for detecting touchdown of the read/write head on its recording surface or for detecting other read signal amplitude modulations as proportional to variance of the value of the read channel variable gain amplifier (“VGA”). Variance in the VGA values caused by the standard feedback control electronics associated therewith is proportional to amplitude modulations of the sensed signal picked up by the read channel (or servo read sensor). These amplitude modulations are, in turn, reflective of flying height of the read/write head as well as generally indicative of other parameters of the read channel operation. Touchdown of the read/write head and other parameters of the disk drive operation may therefore be detected as variances in the VGA control values.Type: GrantFiled: May 27, 2005Date of Patent: April 14, 2009Assignee: Maxtor CorporationInventors: Curtis Egan, David R. Finamore
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Patent number: 7511910Abstract: Systems and techniques relating to interpreting signals on a channel having an asymmetrical signal amplitude response. A signal processor, such as a read channel transceiver device usable in a magnetic recording system, includes an asymmetry correction circuit configured to receive an analog signal and to compensate for asymmetry in the received analog signal, a signal equalizer configured to receive an input signal responsive to an output of the asymmetry correction circuit and to generate an equalized signal, a discrete time sequence detector operable to examine the equalized signal, and a control circuit operable to provide a coefficient adjustment to the asymmetry correction circuit to affect the asymmetry compensation based on an estimate of nonlinearity derived from the equalized signal and multiple output values of the discrete time sequence detector, the multiple output values being values corresponding to at least two different discrete times.Type: GrantFiled: March 28, 2005Date of Patent: March 31, 2009Assignee: Marvell International Ltd.Inventor: Ke Han
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Patent number: 7508611Abstract: A disk drive clock circuit includes a servo clock generator and a disk locked frequency converter. The servo clock generator generates a servo clock signal in response to servo information read from a data storage disk in a disk drive. The disk locked frequency converter responds to the servo clock signal by generating a modified clock signal having a different frequency, and adjusts timing of an edge of the modified clock signal in response to a timing event identified from the servo information read from the disk. The disk locked frequency converter can include a divide-by-n counter that is configured to divide the frequency of the servo clock signal by a number n to generate the modified clock signal. The disk locked frequency converter can reset the divide-by-n counter to a defined value in response to the timing event. The modified clock signal can thereby be phase locked to the servo information on the disk.Type: GrantFiled: October 4, 2006Date of Patent: March 24, 2009Assignee: Seagate Technology, LLCInventors: Bruce Buch, Pei-hui Zheng
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Patent number: 7486457Abstract: A method and apparatus for predicting write failure resulting from flying height modulation and initiating re-writing of data upon occurrence of the predicted write failure is disclosed. According to the present invention, if the slider or transducer flying height modulates during the write process, such modulation is detected, and a rewrite of the same data is forced. A write reassign may be initiated when a thermal signal exceeding the predetermined threshold is detected during the rewrite and/or a read/verify may be initiated after the rewrite.Type: GrantFiled: February 15, 2002Date of Patent: February 3, 2009Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: David H. Jen, Mike Suk
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Patent number: 7483227Abstract: Methods are disclosed for detecting a thermal asperity condition of a head that is configured to generate a read signal by reading data on a rotatable data storage disk in a disk drive. The read signal includes a data component and a thermal component. The read signal is compared to a thermal asperity threshold to detect occurrence of an excessive level of the thermal component of the read signal as a thermal asperity condition of the head. The thermal asperity threshold is varied in response to a rate of occurrence of data value transitions in the data component of the read signal. The thermal asperity threshold can be increased in response to a decrease in the rate of occurrence of data value transitions, and can be decreased in response to an increase in the rate of occurrence of data value transitions. By varying the thermal asperity threshold, the sensitivity of the thermal asperity detector may be improved to allow lower level thermal asperity conditions to be detected with increased accuracy.Type: GrantFiled: May 30, 2006Date of Patent: January 27, 2009Assignee: Maxtor CorporationInventors: Jinghuan Chen, Raymond Pavlak, Jr., Jingfeng Liu
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Patent number: 7457064Abstract: Embodiments in accordance with the present invention provide a perpendicular magnetic recording medium which is easy to record, offers superior thermal stability of recording magnetization, and allows high-density recording. In one embodiment, a perpendicular magnetic layer with controlled magnetic properties is used as a magnetic storage layer of a perpendicular magnetic recording medium, the magnetic properties having been controlled such that an indicator ?hsw [%] of the dispersion of magnetization switching fields in the perpendicular magnetic layer and an indicator Dn [nm] of the intensity of exchange interactions, in film surface directions, in the perpendicular magnetic layer satisfy inequalities ?hsw/27+Dn/90<1, and Dn>20. The indicators can be measured using a magnetometer.Type: GrantFiled: March 6, 2007Date of Patent: November 25, 2008Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hiroaki Nemoto, Ikuko Takekuma, Yuzuru Hosoe