Edgar D Sheh

US Patent:

6529654, Mar 4, 2003

Filed:

May 2, 2001

Appl. No.:

09/847868

Inventors:

Richard Koonwai Wong - San Jose CA
Edgar D. Sheh - San Jose CA
Jenghung Chen - Cupertino CA
Xiao Yang - Fremont CA
Michael Barrett Wolfson - San Jose CA

Assignee:

Nayna Networks, Inc. - Milpitas CA

International Classification:

G02B 626

US Classification:

385 16, 385 17, 385 18

Abstract:

A method for switching signals using one of a plurality of mirrors in an array structure. The method includes determining an optical path to be formed between an input fiber and an output fiber. The method also includes determining a set of mirrors to be used to form the optical path. The set of mirrors includes at least a first mirror. The first mirror is coupled to a mechanical spring assembly and an actuation assembly. The method captures an analog signal indicative of a spatial position of the first mirror using a position sensing device. The sensing device is coupled to the mirror. The method also converts the signal analog signal into a digital signal. The method processes the digital signal indicative of the spatial position of the mirror using the digital signal processing device to obtain a characteristic of the mirror. The method provides a control signal based upon the characteristic of the mirror. The converts the control signal into an analog control signal.

US Patent:

6614618, Sep 2, 2003

Filed:

Mar 31, 2000

Appl. No.:

09/538931

Inventors:

Edgar D. Sheh - Cupertino CA
Thao P. Trieu - Redwood City CA
Ara W. Nazarian - Tustin CA
Richard K. Wong - San Jose CA

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 5596

US Classification:

360 7809

Abstract:

Disclosed is a disk drive having a plant with a moveable transducer and a servo controller that more precisely controls the transducer during short to medium seeks by producing a multi-rate feed-forward command effort signal. The servo controller includes a reference position generator that provides a reference position signal that varies as a function of time along a shaped position profile for moving the transducer from a start position to a target position in a smoothly controlled fashion, a feed-forward control path that receives the reference position signal and applies a feed-forward command effort signal at a feed-forward rate that is greater than the servo sampling rate to move the actuator more closely along the shaped position profile between servo samples; and a feedback control path that receives the reference position signal and the indicated position signal and applies a feedback command effort signal at the servo sampling rate based on a difference between the reference position signal and the indicated position signal to make minor corrections to error remaining after application of prior feed-forward command effort signals.

US Patent:

6693764, Feb 17, 2004

Filed:

Jan 31, 2001

Appl. No.:

09/775256

Inventors:

Edgar D. Sheh - San Jose CA
Hemant Melkote - San Jose CA
Vinay K. Agarwal - Cupertino CA

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 5596

US Classification:

360 7708

Abstract:

The present invention may be embodied in a method and a disk drive for improving head position accuracy during track following through real-time identification of external vibration. A selected track is followed using a servo control loop having a nominal gain and being responsive to position error signal samples generated based on a difference between head position samples and a reference head position value. A spectral power value within a predetermined frequency band is determined from a sequence of the position error signal samples. If a property of the spectral power value exceeds a threshold, the gain of the servo control loop is increased within the predetermined frequency band to attenuate the effect of external vibration on the position of the head over the selected track during track following.

US Patent:

7068459, Jun 27, 2006

Filed:

Sep 20, 2004

Appl. No.:

10/946462

Inventors:

Robert L. Cloke - Santa Clara CA, US
Siri S. Weerasooriya - Campbell CA, US
Tehri S. Lee - San Jose CA, US
Edgar D. Sheh - San Jose CA, US
Wing Ying - Fremont CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 51, 360 7707

Abstract:

A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

US Patent:

7391583, Jun 24, 2008

Filed:

Jul 27, 2006

Appl. No.:

11/494240

Inventors:

Edgar D. Sheh - San Jose CA, US
Tehri S. Lee - San Jose CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 5/09
G11B 21/02
G11B 5/596

US Classification:

360 48, 360 51, 360 75, 360 7708

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.

US Patent:

7391584, Jun 24, 2008

Filed:

Nov 7, 2006

Appl. No.:

11/593929

Inventors:

Edgar D. Sheh - San Jose CA, US
Yilin Cai - Fremont CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 5/09
G11B 21/02

US Classification:

360 51, 360 75

Abstract:

A method of servo writing 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 periodically by a sync mark. A timing recovery measurement is generated in response to the sync marks, wherein the timing recovery measurement comprises a sinusoidal component. A timing compensation value is generated in response to the sync marks which estimates the sinusoidal component in the timing recovery measurement. A frequency control signal is generated in response to the timing recovery measurement and the timing compensation value, a servo write clock is generated in response to the frequency control signal, and the servo write clock and the head internal to the disk drive are used to write the product servo sectors to the disk.

US Patent:

7457071, Nov 25, 2008

Filed:

Aug 8, 2006

Appl. No.:

11/500568

Inventors:

Edgar D. Sheh - San Jose CA, US

Assignee:

Western Digital Technologies, Inc. - Lake Forest CA

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 48, 360 7708

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.

US Patent:

8498076, Jul 30, 2013

Filed:

Apr 22, 2010

Appl. No.:

12/765620

Inventors:

Edgar D. Sheh - San Jose CA, US
Yakov M. Lifchits - San Jose CA, US
Charles A. Park - Aromas CA, US

Assignee:

Western Digital Technologies, Inc. - Irvine CA

International Classification:

G11B 21/02

US Classification:

360 75, 360 51

Abstract:

In an embodiment of the present invention, a disk drive comprises a head actuated over a disk including 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 spiral track crossings. A plurality of timing recovery measurements are generated corresponding to the detected sync marks, and the timing recovery measurements are biased based on a radial location of the head. A servo write clock is generated in response to the biased timing recovery measurements, and the servo write clock is used to write product servo sectors to the disk.