Christopher C J Silva

US Patent:

7321641, Jan 22, 2008

Filed:

Jun 3, 2004

Appl. No.:

10/860232

Inventors:

Andrew Alfred Moulthrop - Los Angeles CA, US
Michael Steven Muha - Torrance CA, US
Christopher Patrick Silva - Rancho Palos Verdes CA, US

Assignee:

The Aerospace Corporation - El Segundo CA

International Classification:

H03D 3/22

US Classification:

375332

Abstract:

A communications system reduces downconverter inaccuracies in time-domain measurements or samples of received microwave communications I and Q complex signals by converting received signal to baseband taking measurements or samples of the I and Q waveforms at differing phase shifts of a demodulating carrier signal for a local oscillator or carrier tracking loop used during downconversion so that I and Q imbalances may be detected and removed by lowpass equivalent averaging for improved characterization of downconverters or for improved signal reception. In the preferred form, the phase shifts are 0 and π/2 for a conventional measurement, and then at θ, and θ+π/2, with θ=π/4+mπ/2 for an integer m for the second measurement where I and Q imbalances and baseband nonlinearities are indicated by differences between the two measured or sampled signals, where θ provides for optimum error detection for reducing the errors by averaging the measurements.

US Patent:

7583759, Sep 1, 2009

Filed:

Jan 18, 2008

Appl. No.:

12/016638

Inventors:

Andrew Alfred Moulthrop - Los Angeles CA, US
Michael Steven Muha - Torrance CA, US
Christopher Patrick Silva - Rancho Palos Verdes CA, US

Assignee:

The Aerospace Corporation - El Segundo CA

International Classification:

H04L 27/22

US Classification:

375332

Abstract:

A communications system reduces downconverter inaccuracies in time-domain measurements or samples of received microwave communications I and Q complex signals by converting received signal to baseband taking measurements or samples of the I and Q waveforms at differing phase shifts of a demodulating carrier signal for a local oscillator or carrier tracking loop used during downconversion so that I and Q imbalances may be detected and removed by lowpass equivalent averaging for improved characterization of downconverters or for improved signal reception. In the preferred form, the phase shifts are 0 and π/2 for a conventional measurement, and then at θ, and θ+π/2, with θ=π/4+mπ/2 for an integer m for the second measurement where I and Q imbalances and baseband nonlinearities are indicated by differences between the two measured or sampled signals, where θ provides for optimum error detection for reducing the errors by averaging the measurements.

US Patent:

62116630, Apr 3, 2001

Filed:

May 28, 1999

Appl. No.:

9/322270

Inventors:

Andrew Alfred Moulthrop - Los Angeles CA
Michael Steven Muha - Torrance CA
Christopher Joseph Clark - Hermosa Beach CA
Christopher Patrick Silva - Rancho Palos Verdes CA

Assignee:

The Aerospace Corporation - El Segundo CA

International Classification:

G01R 2316
G01S 740

US Classification:

324 7623

Abstract:

A time-domain baseband measurement method measures modulated microwave signals typically used in communication systems by converting microwave signals to baseband before measurement for improved accuracy compared to direct measurement at the microwave frequency. A downconverting receiver is first characterized using a prior characterization method and then the modulated microwave signal is applied to the downconverting receiver and the response of the downconverting receiver is removed to provide an accurate characterization of the modulated microwave signal. Such an accurate measurement of the modulated microwave signal can be used for communications system performance verification as well as for characterizing communications devices and systems. One particular application is the measurement of input/output characteristics of nonlinear power amplifiers using such modulated microwave signals.