Automated Interferometric Noise Measurement

An automated interferometric noise measurement system, comprising:

• a signal source adapted to provide a carrier signal;
• a delay line adapted to delay a first version of the carrier signal to provide a delayed signal;
• a variable attenuator adapted to attenuate a second version of the carrier signal to provide an attenuated signal;
• a first variable phase-shifter adapted to phase-shift the attenuated signal to provide a first phase-shifted signal;
• a hybrid coupler adapted to receive the delayed signal and the first phase-shifted signal to provide a carrier-suppressed signal and a carrier-enhanced signal;
• a low-noise amplifier adapted to amplify the carrier-suppressed signal to provide an amplified signal;
• a second variable phase-shifter adapted to phase-shift a version of the carrier-enhanced signal to provide a second phase-shifted signal;
• a first mixer adapted to mix a first version of the amplified signal and the second phase-shifted signal to provide a first noise signal;
• and
• a controller adapted to control the variable attenuator, the first and second phase-shifters, and the low-noise amplifier responsive to a zero-crossing value in the first noise signal, whereby the first noise signal provides a measure of a noise floor for the signal source.

An automated interferometric noise measurement system, comprising:

• a signal source adapted to provide a carrier signal;
• a delay line adapted to delay a first version of the carrier signal to provide a delayed signal;
• a variable attenuator adapted to attenuate the delayed signal to provide an attenuated signal to an amplifier device-under-test (DUT);
• a first variable phase-shifter adapted to phase-shift a second version of the carrier signal to provide a first phase-shifted signal;
• a hybrid coupler adapted to receive an output signal from the amplifier DUT and the first phase-shifted signal to provide a carrier-suppressed signal and a carrier-enhanced signal;
• a low-noise amplifier adapted to amplify the carrier-suppressed signal to provide an amplified signal;
• a second variable phase-shifter adapted to phase-shift a version of the carrier-enhanced signal to provide a second phase-shifted signal;
• a first mixer adapted to mix a first version of the amplified signal and the second phase-shifted signal to provide a first noise signal;
• and
• a controller adapted to control the variable attenuator, the first and second phase-shifters, and the low-noise amplifier responsive to a zero-crossing value in the first noise signal.