Nonlinear Noise Measurement on a High Power Amplifier

The common measurements of noise in a communications channel, such as noise figure, are linear measurements. Yet many communications channels are nonlinear because the transmitter is operated close to saturation for high efficiency. We present here a novel method to measure noise in the time domain in the presence of a wideband signal. In conjunction with standard measurements, this new method is applied to measure the output of a traveling wave tube amplifier (TWTA) driven into saturation with a wideband signal in order to derive an accurate black-box model of the TWTA including noise.