Andrew Wayne Davidson

US Patent:

50477250, Sep 10, 1991

Filed:

Nov 28, 1989

Appl. No.:

7/443213

Inventors:

Eric W. Strid - Portland OR
Andrew C. Davidson - Portland OR

Assignee:

Cascade Microtech, Inc. - Beaverton OR

International Classification:

G01R 2704

US Classification:

324601

Abstract:

A method for correcting inaccuracies in error factors of an error model used for vector-corrected, microwave-frequency measurements. Verifying de-embedded measurements are compared to known characteristics of at least one verification standard. At least one parameter of the calibration standards, or an error factor, or measuring network geometry, is changed and the error factors are recalculated to bring the verifying measurements into conformity with the known characteristics of the verification standard.

US Patent:

49053086, Feb 27, 1990

Filed:

Apr 5, 1989

Appl. No.:

7/333633

Inventors:

Andrew C. Davidson - Portland OR

Assignee:

Cascade Microtech, Inc. - Beaverton OR

International Classification:

G01S 740
G01R 2728

US Classification:

455226

Abstract:

A method of determining a receiver's noise parameters by measuring one noise power for a first source noise temperature and a plurality of noise powers for another source noise temperature, all at known different source reflection coefficients.

US Patent:

48642185, Sep 5, 1989

Filed:

Nov 9, 1988

Appl. No.:

7/269970

Inventors:

Bernard W. Leake - Beaverton OR
Andrew C. Davidson - Portland OR

Assignee:

Cascade Microtech, Inc. - Beaverton OR

International Classification:

G01S 740
H04B 116

US Classification:

324 57N

Abstract:

A method of measuring and compensating for measurement frequency inaccuracies encountered when measuring noise power of a device under test within a desired calibrating frequency range. The method includes sweeping a frequency synthesizer through a frequency range which includes the desired measurement frequency range. Power is measured for different synthesizer frequencies with the noise power meter set to the desired frequency range. Alternatively, the frequency synthesizer may be set to the desired measurement frequency and the noise power meter swept through a range including the desired measurement frequency. The resulting power measurements show the frequency range within which the noise power meter actually measured power. The difference between the desired measurement frequency range and the actual measurement frequency range is the measurement frequency error which may be corrected using a frequency conversion stage to displace test signals by the amount of the measurement frequency error before they are sent to the noise power meter.

US Patent:

51592622, Oct 27, 1992

Filed:

Jul 9, 1991

Appl. No.:

7/727566

Inventors:

Scott H. Rumbaugh - Lake Oswego OR
Andrew C. Davidson - Portland OR

Assignee:

Cascade Microtech, Inc. - Beaverton OR

International Classification:

G01R 2704
G06F 1520

US Classification:

324158R

Abstract:

A method for on-wafer testing of microwave devices, such as photodiodes, including a biasing method applicable when the device has a lower end connected to the ground plane of the wafer. Elements having a diode-like characteristic, such as photodiodes, are arranged side-by-side with the device, each preferably being of like geometry with the device, and each having an end connected to the ground plane. A first voltage is applied between the ground conductors of the probe and the ground plane of the wafer to place each element in forward-biased condition thereby creating a return path for the lower end of the device to the ground conductors located on the upper side of the wafer. The method further includes a calibration method for accurate measurements of photodetectors particularly when they are biased as described above, including measuring a performance parameter, such as responsivity, that characterizes the optical performance of the photodetector, measuring a network parameter, such as a reflection coefficient, that characterizes the electrical performance of the photodetector, and determining an adjusted value for the performance parameter based on the network parameter in which the reference plane of the measured performance parameter has been shifted so as to better characterize the intrinsic response of the photodetector without interference by the surrounding measurement environment. Specific steps for removing probe effects and return path diode effects are described.