Uncertainty of a Millimeter-Wave Variable Noise Source using a Variable Attenuator

We studied a variable noise source using a precision variable attenuator in the frequency range of 50 - 75 GHz, and its uncertainty was analyzed in detail. To determine the noise temperature of the noise source, the variable attenuator was calibrated by the national standard of attenuation in NMIJ. It was proved that the contribution of uncertainty concerning the variable attenuator was considerably small by achieving its precise calibration. This variable noise source can be used as a working standard for the millimeter-wave noise figure measurement.