George A Walker

US Patent:

8374811, Feb 12, 2013

Filed:

Dec 7, 2009

Appl. No.:

12/631968

Inventors:

Steven K. Sullivan - Beaverton OR, US
Kristie L. Veith - Portland OR, US
Terrance R. Beale - Portland OR, US
Paul M. Gerlach - Beaverton OR, US
Gregory A. Martin - Portland OR, US
George S. Walker - Beaverton OR, US

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

G06F 19/00
G01R 13/02

US Classification:

702 68

Abstract:

A waveform display apparatus and method displays one or more waveforms of a signal under test at high throughput while acquiring digital data of the signal under test in a large acquisition memory. A user sets a time interval of user's interest when viewing a signal under test and sets trigger criteria through a user interface. An ADC converts the signal under test into digital data that is stored in a large acquisition memory. A trigger unit detects and produces trigger events, based on a trigger, as trigger event information during one acquisition process. A trigger event eliminator may discard some of the trigger events based on pre-trigger and post-conditions set through the interface by a user. The trigger events are recorded in a trigger list as the trigger event information. A control unit locates the digital data in the acquisition memory corresponding to the trigger events in the trigger list and displays a waveform associated with the trigger event for the time interval on a display device.

US Patent:

59951176, Nov 30, 1999

Filed:

Feb 19, 1998

Appl. No.:

9/026186

Inventors:

Kenneth P. Dobyns - Beaverton OR
Robert A. Nishida - Hillsboro OR
George S. Walker - Beaverton OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G06F 1500

US Classification:

345441

Abstract:

One or more recently acquired waveform data sets are maintained in memory after they are initially rasterized. During repeated waveform acquisitions, when the trigger and new waveform acquisition rates become so low that rasterizer time is being wasted, one or more of the most recent previously acquired waveforms are re-rasterized and displayed again to maintain the display until another newly acquired waveform becomes available. The rasterizer's readiness to re-rasterize a previously rasterized waveform data set can be qualified with a pre-determined or programmable time delay, thereby providing more flexibility for external circuitry and controllers to optimize utilization of the rasterizer's behavior. The method of this invention works especially well with rasterizers that produce some form of randomization in their outputs.

US Patent:

53529766, Oct 4, 1994

Filed:

Jan 31, 1992

Appl. No.:

7/828827

Inventors:

George S. Walker - Beaverton OR
Eric P. Etheridge - Beaverton OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G01R 2500

US Classification:

324121R

Abstract:

A multi-channel trigger dejitter technique uses actual digitized samples from a repetitive waveform signal to correct for jitter in a hardware trigger signal. Interpolated samples are calculated between a set of the digitized samples about the hardware trigger signal, and a hardware trigger level is determined from the closest sample in time to the hardware trigger signal. The hardware trigger level is averaged with that determined from prior acquisitions to produce an average trigger level. The closest sample in time to the average trigger level becomes an averaged trigger signal, and the times for all the digitized samples for that acquisition, as well as all simultaneous acquisitions from other input channels, are adjusted according the difference in time between the hardware and averaged trigger signals. Over several acquisition iterations of the repetitive waveform the amount of jitter between acquisitions is decreased.

US Patent:

48433098, Jun 27, 1989

Filed:

Mar 21, 1988

Appl. No.:

7/171060

Inventors:

Arif Kareem - Beaverton OR
George S. Walker - Beaverton OR
Daniel G. Knierim - Beaverton OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

G01R 2500
G01R 2504

US Classification:

324121R

Abstract:

A method and an apparatus detect the presence of and correct for timing misalignment between waveforms acquired by digital oscilloscopes. In a preferred embodiment, a digital oscilloscope (50) includes a waveform alignment system (60) that receives a first waveform (86) and a similar second waveform (88) of a periodic electrical signal. A digital signal processor (80) of the waveform alignment system generates an autocorrelation value in connection with the first waveform and a first cross-correlation value in connection with the first and second waveforms and compares the values to determine whether they differ by more than a preselected tolerance, thereby to detect a timing misalignment between the first and second waveforms. Upon detection of a timing misalignment, the digital signal processor computes a shifted second waveform by changing the timing relationship of the second waveform relative to the first waveform and generates a second cross-correlation value in connection with the first waveform and the shifted second waveform. The digital signal processor shifts the second waveform relative to the first waveform such that the second cross-correlation value differs from the autocorrelation by less than the preselected tolerance, thereby to correct the timing misalignment.