Grant S Christiansen

US Patent:

6369969, Apr 9, 2002

Filed:

Feb 28, 2001

Appl. No.:

09/797446

Inventors:

Grant S. Christiansen - Rochester MN
Mark D. Hagen - Rochester MN

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 509

US Classification:

360 66, 360 51, 360 59, 369 533

Abstract:

A disk drive is disclosed comprising a bias layer in a magnetoresistive (MR) head actuated over a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector, wherein when the sync mark pattern is detected a sync mark detect signal and a polarity signal are generated. The polarity signal indicates when the polarity of the bias layer has deviated from a preferred polarity, wherein the polarity of the bias layer is realigned back toward the preferred polarity.

US Patent:

6603622, Aug 5, 2003

Filed:

Feb 28, 2001

Appl. No.:

09/796838

Inventors:

Grant S. Christiansen - Rochester MN
Mark D. Hagen - Rochester MN

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 509

US Classification:

360 66, 360 48, 360 45, 360 46, 360 51

Abstract:

The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector by filtering a read signal with a matched filter having an impulse response substantially matched to a dibit response of the disk drive. The output of the matched filter is correlated with a dual polarity correlator to generate first and second correlated signals. The sync mark pattern is detected when either the first or second correlated signals exceeds a threshold.

US Patent:

6639748, Oct 28, 2003

Filed:

Feb 28, 2001

Appl. No.:

09/796933

Inventors:

Grant S. Christiansen - Rochester MN
Mark D. Hagen - Rochester MN

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 509

US Classification:

360 66, 360 51, 360 59, 360 48, 360 49

Abstract:

The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector, wherein when the sync mark pattern is detected a sync mark detect signal and a polarity signal are generated. The polarity signal represents an expected polarity of pulses in a read signal representing data stored in the sector, wherein the polarity signal enhances the detection of an estimated data sequence from the read signal.

US Patent:

20020181055, Dec 5, 2002

Filed:

Aug 6, 2001

Appl. No.:

09/923510

Inventors:

Grant Christiansen - Rochester MN, US
Karl Northrup - Rochester MN, US
Robert Keller - Plano TX, US
Jose Melendez - Plano TX, US
John So - Plano TX, US

International Classification:

H04B010/00

US Classification:

359/159000, 359/172000

Abstract:

Optical wireless links communicate beam alignment information between them over a collimated, modulated light beam, without the requirement of a secondary channel. The alignment feedback signal can be formatted as control packets that are inserted between data packets traveling over the optical wireless channel, as control packets that are combined with the data packets, as a low frequency modulation of the light beam, or similar approaches. Alignment feedback signals are used by the device receiving the signal to align its light beam using a beam steering device, such as a micro-mirror device. Control signals preferably include x and y coordinate information relating to the position of both devices that are communicating, as well as time stamp, sample number, and similar synchronization information. Control packets are extracted from the data stream by a switch based upon the destination address of the control packets.

US Patent:

20040208529, Oct 21, 2004

Filed:

May 14, 2002

Appl. No.:

10/145974

Inventors:

James Noxon - Rochester MN, US
Karl Northrup - Rochester MN, US
Grant Christiansen - Rochester MN, US

International Classification:

H04B010/00

US Classification:

398/033000

Abstract:

A method of implementing packet corruption to halt propagation in an optical wireless communication link in a manner that simultaneously minimizes network overhead and maintains a high bandwidth loop sufficient to control the motion of the mirror.

US Patent:

20040208611, Oct 21, 2004

Filed:

Apr 24, 2002

Appl. No.:

10/131445

Inventors:

Eric Oettinger - Rochester MN, US
Mark Heminger - Rochester MN, US
Mark Hagen - Rochester MN, US
Karl Northrup - Rochester MN, US
Robert Jansen - Byron MN, US
James Noxon - Rochester MN, US
Grant Christiansen - Rochester MN, US

International Classification:

H04B010/00

US Classification:

398/149000

Abstract:

A technique that eliminates or minimizes the effects of reflective surfaces to reduce or eliminate interference in the data stream and allow an optical wireless communication link to be used reliably. The most important reflective surface is the reflective surface in front of the data detector itself, as that is the one that will be reflected after the transmitting and receiving stations are properly aligned. The greatest reduction in reflected data associated with a remote detector is then achieved by angling the surface in front of the data detector itself, such that reflections from that surface will not fall within the field of view of the remote detector once the stations are properly aligned.

US Patent:

60497637, Apr 11, 2000

Filed:

Nov 3, 1997

Appl. No.:

8/962627

Inventors:

Grant Stolpe Christiansen - Rochester MN
Donald Earl Vosberg - Rochester MN

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G11B 2010
G11B 502

US Classification:

702133

Abstract:

An improved thermal asperity detector is disclosed for detecting short thermal asperities using a variable time threshold. The thermal asperity detector includes a saturation detector, and a comparator system. The comparator system may include a polarity latch, a processor, a level comparator and a timing comparator. The saturation detector compares a programmable saturation threshold to an A/D sample to generate an enable signal in response to the A/D sample exceeding the saturation threshold. The polarity latch receives the A/D sample and the enable signal, and records the most significant bit of the A/D sample to identify the polarity of the saturation and to provide an output signal representative thereof in response to the enable signal. The processor generates a threshold level control signal based upon a programmable level threshold and the polarity latch output signal. The level comparator compares the A/D sample and the output from the polarity latch in response to the enable signal, and generates a timing output signal to a timing comparator in response to the comparison of the A/D sample and the output from the polarity latch.