Direct and Accurate Measurements of Mixer Equivalent Noise Temperatures

A new measuring technique has been developed, which enables the effective noise temperature Teff and intrinsic conversion loss Li of a lossy 2-port network to be determined directly. This technique when applied to a mixer, yields results which are in agreement with theoretical predictions (0.5 ¿ Teff ¿ To; To ambient temperature) and may be measured with greater accuracy than has previously been possible using other methods. Practical results will be presented together with theoretical predictions based on a new approach to mixer noise analysis. This approach gives greater insight into the noise generation mechanisms and is more readily interpreted than other methods published to date in the literature.