PT Unknown AU Gerecht, E Musante, CF Wang, Z Yngvesson, KS Waldman, J Gol'tsman, GN Yagoubov, PA Svechnikov, SI Voronov, BM Cherednichenko, SI Gershenzon, EM TI NbN hot electron bolometric mixer for 2.5 THz: the phonon cooled version SE Proc. 8[super:th] Int. Symp. Space Terahertz Technol. PY 1997 BP 258 EP 271 DE NbN HEB mixers AB We describe an investigation of a NbN HEB mixer for 2.5 THz. NbN HEBs are phonon-cooled de-. vices which are expected, according to theory, to achieve up to 10 GHz IF conversion gain bandwidth. We have developed an antenna coupled device using a log-periodic antenna and a silicon lens. We have demon- strated that sufficient LO power can be coupled to the device in order to bring it to the optimum mixer oper- ating point. The LO power required is less than 1 microwatts as measured directly at the device. We also describe the impedance characteristics of NbN devices and compare them with theory. The experimental results agree with theory except for the imaginary part of the impedance at very low frequencies as was demonstrated by other groups. ER