NBN HOT-ELECTRON SUPERCONDUCTING MIXERS FOR 100 GHZ OPERATION

NbN is a promising superconducting material for hot-electron supercond ucting mixers with an IF bandwidth larger than 1 GHz. In the 100 GHz f requency range, the following parameters were obtained for 50 Angstrom thick NbN films at 4.2 K: receiver noise temperature (DSB) similar to 1000 K; conversion loss similar to 10 dB; IF bandwidth similar to 1 G Hz; and local oscillator power similar to 1 mu W. An increase of the c ritical current of the NbN film, increased working temperature, and a better mixer matching may allow a broader IF bandwidth up to 2 GHz, re duced conversion losses down to 3-5 dB and a receiver noise temperatur e (DSB) down to 200-300 K.