A noise parameter test setup allows accurately measuring the four noise parameters (Fmin, Rn, ┌opt) of microwave transistors over a wide frequency range using two distinct wideband measurement paths, based on differential wafer probes, instead of SPDT switches, to commute between s-parameter (signal) measurement and noise measurement path, avoiding thus the uncertainty of the accuracy as well limited availability of SPDT switches. Calibration of the system is the same as when using switches, when hopping the DUT chip from one set or subset of probes to the next. Additional power control precautions of the VNA sources are necessary to avoid injecting signal power into the sensitive noise receiver during s-parameter measurements and jamming the weak noise power during noise measurement.