PT Journal AU Karasik, BS Elantiev, AI TI Noise temperature limit of a superconducting hot-electron bolometer mixer SO Applied Physics Letters JI Appl. Phys. Lett. PY 1996 BP 853 EP 855 VL 68 IS 6 DI 10.1063/1.116555 DE HEB mixer noise temperature; Johnson noise; thermal fluctuation noise; noise bandwidth ER