A wide-band on-wafer noise parameter measured ment system at 50-75 GHz is presented. This measurement system is based on the, cold-source, method with a computer-controlled waveguide tuner. Calibrations and measurement methods are discussed and measured results for passive and act devices are shown over a 50-75-GHz range. An InP high electron-mobility transistor device is used as a test item for the active device. A Monte Carlo analysis. to study measurement uncertainties is also shown. The measurement system is a useful tool in the development and verification of device noise models, as well as in device characterization.