Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
2005-03-08
2005-03-08
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S048000, C360S075000
Reexamination Certificate
active
06865041
ABSTRACT:
A method and apparatus for servowriting using a unipolar write current is disclosed. A track for writing a servo pattern is determined and the servo pattern is written using a unipolar write current pulse. The writing of the servo pattern using the unipolar write current pulse creates a servo pattern having less of an erase band and wider track width than if the servo pattern was produced by a bipolar write current pulse. The unipolar write current pulse is applied across a write gap formed by a first pole and a second pole, and wherein a field extension next to the first pole extends further and creates a narrower side erase band than the field proximate to the second pole. The write current pulse width is controlled to set a magnetization length in the servo pattern created in the disk. Analog characteristic of a digital control signal in a variable width pulse generator is set to control a width of the write current pulse to control a magnetization length in the servo pattern created on the disk.
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Arnoldussen Thomas Claude
Hong Ju-Hi John
Wood Roger William
Crawford & Maunu PLLC
Davidson Dan I.
Hitachi Global Storage Technologies - Netherlands B.V.
Hudspeth David
LandOfFree
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