Patent ID: 8363849
Filing Date: 2013-01-29
Classification: G01R

Abstract:
1. An automated interferometric noise measurement system, comprising: a signal source adapted to provide a carrier signal; a delay line connected to receive the carrier signal, the delay line configured to delay the carrier signal to provide a delayed signal to a device-under-test (DUT) along a first signal path; a variable attenuator connected to receive the carrier signal, the variable attenuator configured to attenuate the carrier signal to provide an attenuated signal along a second signal path in parallel with the first signal path; a first variable phase-shifter configured to phase-shift the attenuated signal to provide a first phase-shifted signal along the second signal path; a hybrid coupler connected to the first signal path at a first hybrid coupler input to receive an output signal from the DUT, and to the second signal path at a second hybrid coupler input to receive the first phase-shifted signal, the hybrid coupler configured to provide a carrier-suppressed signal at a first output of the hybrid coupler and a carrier-enhanced signal at a second output of the hybrid coupler; a low-noise amplifier connected along a third signal path to the first output of the hybrid coupler, the low-noise amplifier configured to amplify the carrier-suppressed signal to provide an amplified signal; a second variable phase-shifter connected along a fourth signal path to the second output of the hybrid coupler, the second variable phase-shifter configured to phase-shift the carrier-enhanced signal to provide a second phase-shifted signal; a first mixer connected along the third signal path to the low-noise amplifier at a first mixer input and along the fourth signal path to the second variable phase-shifter at a second mixer input, the first mixer configured to mix the amplified signal from the low-noise amplifier and the second phase-shifted signal from the second variable phase-shifter to provide a first noise signal; and a controller configured 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.