Okunev, 0., Dzardranov, A., Gol'tsman, G., & Gershenzon, E. (1995). Performances of hot—electron superconducting mixer for frequencies less than the gap energy: NbN mixer for 100 GHz operation. In _Proc. 6<sup>th</sup> Int. Symp. Space Terahertz Technol._ (pp. 247&ndash;253).