PT Unknown AU Ynvesson, KS Kollberg, EL TI Optimum receiver noise temperature for NbN HEB mixers according to standard model SE Proc. 10[super:th] Int. Symp. Space Terahertz Technol. PY 1999 BP 566 EP 582 DE HEB mixer model; standard model; electro-thermal feedback; self-heating parameter; heating efficiency ER