Noise partition in S-parameter measurement

The noise in vector network analyzer (VNA) and time domain reflectometer (TDR) is analyzed from perspective principle of operation and instrument hardware, complementing the metrological and black-box modeling, which use phenomenological input for the noise. The analyses and experiments confirm a noise partition in the S-parameter measurement. The partition is between noise from signal generator and measurement, and between low-frequency plateau and quadratic elevation in the noise spectra at high frequency. The noise scales with the thermal noise in an effective noise bandwidth, signal power and power loss. The noise partition is an input for other models, providing for scaling of the random error with measurement settings, frequency and S-parameter values.