The Aerospace Corporation

Michael Steven Muha

Christopher Patrick Silva

Andrew Alfred Moulthrop

Christopher Joseph Clark

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 &#x3c0;/2 for a conventional measurement, and then at &#x3b8;, and &#x3b8;+&#x3c0;/2, with &#x3b8;=&#x3c0;/4+m&#x3c0;/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 &#x3b8; provides for optimum error detection for reducing the errors by averaging the measurements.

Baseband time-domain communications method

Baseband time-domain communications system

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.

Baseband time-domain waveform measurement method

A three-pair measurement method determines the amplitude and phase transmission response of frequency translating devices including a device under test and two test devices using a vector network analyzer and a controller where one of the devices has reciprocal frequency response characteristics. The characterization of single sideband and double sideband devices such as mixers, is preferably performed by combining data from analyzer two-port swept measurements. The measurement method provides a low-pass equivalent transmission response of the devices.

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Torrance, CA, United States of America

Michael Steven Muha