Mihir K Ravel

US Patent:

6507624, Jan 14, 2003

Filed:

Apr 21, 1999

Appl. No.:

09/296438

Inventors:

Stephen P. Jachim - Portland OR
Mihir K. Ravel - Portland OR
Steven H. Pepper - Portland OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

H03K 900

US Classification:

375316, 375224, 324 7623, 324 7624

Abstract:

A bandpass sampling system ( ) of this invention employs a conventional mixer ( ) driven by a frequency-tunable LO ( ) to upconvert a signal frequency band to an IF frequency band that is above the signal frequency band. The IF frequency band is passed through an IF bandpass filter ( ) to provide to subsequent digitization stages ( ) an IF bandpass range of signal frequency components. In this architecture, the IF bandpass filter acts as an anti-alias filter for the digitization stages. The LO frequency is selected to place the upconverted signal frequency band within the pass band of the IF bandpass filter. The resultant IF bandpass signal is sampled and digitized at a rate that is commensurate with the IF bandwidth, but typically much lower than the IF bandpass center frequency. Signal sampling is carried out by a sample-and-hold or a track-and-hold circuit ( ), the output of which is applied to an ADC ( ) that is clocked ( ) at the same rate as the sampling circuit.

US Patent:

54123305, May 2, 1995

Filed:

Jun 16, 1993

Appl. No.:

8/077905

Inventors:

Mihir K. Ravel - Portland OR
Michael D. Jones - Portland OR
Steven H. Pepper - Portland OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G01R 31308
G01R 3102

US Classification:

324753

Abstract:

An optical module for an optically based measurement system, such as an electro-optic system (10) for measuring electrical characteristics of a device under test (14), has a probe arm (26), a layer of electro-optic material (27), and a first optical system for delivering a measurement beam (44) to the layer and for producing therefrom an information-carrying beam having optical characteristics indicative of the electric characteristics. The first optical system includes a first lens (128), and (optional) polarization bias adjustment (130), a dichroic beamsplitter (112), and a second lens (114). The module also has a second optical system for delivering an observation beam (66) through the layer and onto a portion (68) of the device and for forming from rays (69) stemming from the observation beam a light pattern (70) indicative of the portion. The information-carrying beam is analyzed in a polarization analysis module into component beams (136, 138) in respective linearly independent polarization states. Converters (144, 146) produce electrical signals (147, 148) indicative of the intensity of the respective component beams; alternatively, the component beams are conveyed for analysis elsewhere.

US Patent:

54888662, Feb 6, 1996

Filed:

Apr 11, 1994

Appl. No.:

8/225867

Inventors:

Mihir K. Ravel - Portland OR
Steven H. Pepper - Portland OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G01N 2908

US Classification:

73579

Abstract:

A time-interleaved method for efficient operation of an acoustic wave sensor array couples each sensor repetitively and one at a time via a digitally-addressable analog switch, or multiplexer, to a single oscillator driver to form an oscillation circuit. A frequency of oscillation for each acoustic wave sensor is determined. The frequency for each acoustic wave sensor then is converted into a measurement value for the parameter to which each acoustic wave sensor is sensitive.

US Patent:

54068290, Apr 18, 1995

Filed:

Apr 19, 1994

Appl. No.:

8/229899

Inventors:

Mihir K. Ravel - Portland OR
Steven H. Pepper - Portland OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G01N 3106
G01K 1122

US Classification:

73 2401

Abstract:

A temperature control system for acoustic wave chemical sensors monitors the frequency output from a reference sensor packaged within a heat conductive case with a test sensor. Since the frequency output fluctuates as a function of temperature, variations in frequency from a nominal value representing a desired steady state temperature for the sensors are detected and used as a control signal for a heating element attached to the heat conductive case.