Noise of superconductor/normal metal/superconductor mixer based on low voltage negative differential resistance effect

The conversion efficiency was calculated for some type of high-T/sub c/ superconducting junctions, which have negative derivative on current-voltage characteristics. This distinguishing feature can be explained by Andreev reflections in superconductor/normal metal boundaries. In this work it is analyzed a combination of the theoretical predictions of noise, based on noise correlation matrix of the mixer model, and theory of Likharev-Semenov for the thermal noise. The conversion gain is possible in SNS mixers in spite of noise in negative derivative region.