Noise measurements in the presence of large signal transients and studies of recovery effects

Noise behavior of devices and systems after large signal transients can reveal information about thermal, bias, trapping or hot electron behaviors as well as identify potential practical operational issues for receivers in a dynamic signal environment. A measurement configuration to study these effects is presented that is based on a low noise front-end, isolated synchronously from the large signals, and a wide-IF VNA platform that can capture the resulting noise behavior versus time. For noise floors that may be useful for studying power devices, ns to μs scale resolution was achieved with repeatabilities and relative uncertainties on the order of 1 dB throughout the microwave frequency ranges for some practical noise levels.