Local oscillator noise suppression by a balanced SIS mixer in the 0.9 THz band

Local oscillator (LO) sideband noise suppression by a balanced superconductor-insulator-superconductor (SIS) mixer was investigated in the 0.9 THz band. An LO signal in the 0.9 THz band was generated by using fixed tuned x9 (x3 by x3) multipliers located in the cryostat 4-K stage. Despite the huge LO noise of about 1000 K of a YIG driven LO, the measured receiver noise temperature for YIG and Gunn driven LOs was similar because of the high LO sideband noise rejection ratio (LNR) of the balanced mixer.