International Business Machines Corporation

Hitachi Global Storage Technologies Netherlands B.v.

Ju-Hi John Hong

Wayne Leung Cheung

Kok-Kia Chew

Karl Arnold Belser

David W Albrecht

Roger William Wood

John Jeffrey Stephenson

Mohamad Towfik Krounbi

Satoshi Yamamoto

Michael Paul Salo

Scott Arthur Thomas

Thomas C Arnoldussen

Abraham M Gindi

William K Stelzenmuller

Dave Anthony Freitas

A method and apparatus for servowriting using a unipolar write current is disclosed. A track for writing a servo pattern is determined and the servo pattern is written using a unipolar write current pulse. The writing of the servo pattern using the unipolar write current pulse creates a servo pattern having less of an erase band and wider track width than if the servo pattern was produced by a bipolar write current pulse. The unipolar write current pulse is applied across a write gap formed by a first pole and a second pole, and wherein a field extension next to the first pole extends further and creates a narrower side erase band than the field proximate to the second pole. The write current pulse width is controlled to set a magnetization length in the servo pattern created in the disk. Analog characteristic of a digital control signal in a variable width pulse generator is set to control a width of the write current pulse to control a magnetization length in the servo pattern created on the disk.

Method and apparatus for servowriting using a unipolar write current

A magneto-resistive (M-R) head has a read element with a servo sensing width as wide as a data track width and a data sensing width of less than one data track width. The two read sensing widths are achieved by using a single read element having a center electrical contact from the M-R read element that effectively reduces the sensing width of the read element. In a first embodiment, the servo sensing width comprises a first portion of the read element and the data sensing width comprises a second, smaller portion of the read element. In a second embodiment, the servo sensing width comprises the entire read element width and the data sensing width comprises a portion thereof. In yet another embodiment, abutting read elements are constructed to enable separate optimization of each sensing width. The wide servo sensing width permits use of a wide servo pattern having servo bursts as wide as a data track width. A position error sensing (PES) signal produced with the wide servo read element and wide servo pattern has increased linearity and accuracy.

Disk drive with wide servo burst pattern and wide servo sensing element

A multi-track density direct access storage device is disclosed. In accordance with a preferred embodiment of the present invention, a direct access storage device for data storage within a data processing system comprises a housing, a rotatable spindle, at least one disk, and several heads. The disk is fixedly mounted to the rotatable spindle, and the rotatable spindle is rotated by a motor within the housing. A first disk surface of the disk has a first track density and a second disk surface of the disk has a second track density; wherein the second track density is preferably greater than the first track density. Each of the several heads contains a transducer to read and write information from and to the disk during the disk rotation. Under this configuration, the lower storage density it first disk surface is utilized to store data that are frequently accessed while the higher storage density second disk surface is for storage capacity supplementation such that the total data storage capacity of the direct access storage device can be increased without degrading the data-accessing performance.

Multi-track density direct access storage device

In accordance with the present invention a storage device servo control system that positions a head relative to multiple tracks of a storage medium includes a servo signal filter that receives a readback signal from the head and produces filtered servo signal data samples, a servo demodulator that receives the filtered readback servo signal from the servo signal filter and produces a position error signal that indicates the head position relative to a track using a demodulation scheme selected in accordance with a track width profile of the storage device, and includes a servo controller that determines the demodulation scheme to be used by the servo demodulator and that processes the position error signal to maintain the head centered relative to the track.

Method and apparatus for providing a linear position error sensing (PES)

A multi-track density direct access storage device is disclosed. In accordance with a preferred embodiment of the present invention, a direct access storage device for data storage within a data processing system comprises a housing, a rotatable spindle, at least one disk, and several heads. The disk is fixedly mounted to the rotatable spindle, and the rotatable spindle is rotated by a motor within the housing. A first disk surface of the disk has a first track density and a second disk surface of the disk has a second track density; wherein the second track density is preferably greater than the first track density. Each of the several heads contains a transducer to read and write information from and to the disk during the disk rotation. Under this configuration, the lower storage density first disk surface is utilized to store data that are frequently accessed while the higher storage density second disk surface is for storage capacity supplementation such that the total data storage capacity of the direct access storage device can be increased without degrading the data-accessing performance.

A servo system accurately detects and processes signals from servo patterns encoded on magnetic storage disks using weighted accumulation, for use in precisely positioning read/write heads with respect to tracks of data contained on the disks. After servo patterns are sensed by reading them from a disk, the resultant servo signals are processed by weighted accumulation circuitry to provide a position signal, which may be decoded to ascertain the positioning error of the read/write head and to apply any corrections that might be needed. In one embodiment, an amplitude position signal is generated by multiplying the servo signal by complementary quadrature weighting signals, then squaring each quadrature output signal, summing them, and taking the square root of the summed signal. In another embodiment, a phase position signal is generated by multiplying the servo signal by complementary quadrature weighting signals, dividing one of the multiplied signals by the other to provide a quotient signal, and then generating a signal corresponding to the arctangent of the quotient signal. The invention may be implemented with analog or digital circuitry. In an analog embodiment, the quadrature output signals are created using multipliers to multiply the servo signal by complementary analog quadrature weighting signals. In a digital embodiment, the output quadrature signals are created using latches to sample the servo signal at predetermined intervals, selectively multiplying sampled signals by predetermined quadrature weighting signals, and accumulating the resulting signals.

Asynchronous position error signal detector employing weighted

A synchronization pattern is provided within an incoming waveform which represents a serial data stream transmitted at a rate determined by a data clock. The synchronization pattern includes a periodic training portion and a sync word portion. The periodic training portion is periodic and has a preselected period. As the periodic training portion is received, a receiver clock phase-locks to the periodic training portion of the incoming waveform, and a sampling circuit periodically samples the incoming waveform relative to the phase and frequency of the receiver clock to produce sample words. Thereafter, a subset of the sample words are selected utilizing a selection pattern having a period equal to the period of the periodic training portion of the incoming waveform. Utilizing the selected subset of sample words, a sync indicator word is produced and compared to preselected criteria. Such a sync indicator word may be produced with reference to the sign of each sample word of the subset of sample words. Finally, in response to a correlation between the sync indicator word and the preselected criteria, byte synchronization between the incoming waveform and the data detector is indicated, wherein the byte synchronization independently from the output of a data detector.

Method and apparatus for determining byte synchronization within a

An error correcting scheme for processing data which is transmitted on a broadband and/or CATV network and utilizes the IEEE 802.4 three-level duobinary AM/PSK (phase shift keying) coding format. The error correcting scheme utilizes two thresholders. One of the thresholders makes data (1 or 0) decisions while the other thresholder makes non-data or no non-data (non-data) decisions. Pattern matching and windowing are used to detect non-data symbols which are corrected if the non-data symbols deviate from a predetermined pattern. The template used in the pattern matching is determined from the state of a demodulator.

Error correction scheme

A protection circuit is provided in which the output voltage is sensed and the output device is shut-off for protection when the output voltage falls below a predetermined trip voltage. The monolithic integrated circuit includes a voltage shifting circuit for transferring the output voltage to a biasing circuit which biases a switching circuit which turns the line driver off, when an overload or short circuit causes a voltage drop below a predetermined trip voltage. The protection circuit is disabled during start-up or signal rise time by splitting the input signal into two separate paths in which the signals have different delays. The shorter delay allowing the input signal to rise and to appear on the output line before the longer delay input signal rises enabling the protection circuit.

Short circuit protection circuit

An improved clock retiming system for pulse coded data is provided in which the clock signals are extracted from the encoded data and first and second signals of the same amplitude and frequency but of different phase are generated from the clock signals. First and second amplifiers having variable gains provide amplification for the first and second signals, respectively. The first and second amplified signals are summed to produce a third signal having a phase which is a function of the relative amplitudes of the first and second amplified signals. The original pulse encoded data is sampled with the third signal to produce the retimed data output. The original pulse encoded data is also utilized to sample the third signal. The resulting signal is filtered to provide a DC voltage feedback error signal indicative of the phase difference between the third signal and the original pulse encoded data. This feedback signal is translated into a pair of complementary signals forming inputs to the first and second amplifiers, respectively, to vary the variable gains thereof, oppositely thereby adjusting the phase of the third signal to correspond to the phase of the original pulse encoded data.

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San Jose, CA, United States of America

Ju-Hi John Hong