Fabrication and Characterization of a 600 GHz

The non-linear quasiparticle tunnel current flowing in a distributed superconductor-insulator-superconductor (SIS) transmission line resonator has been exploited in a low-noise heterodyne fixed-tuned waveguide receiver in the 600 GHz band. The mixer employs two half-wave or full-wave distributed SIS long junctions connected in series. These devices have been fabricated with optical lithography. Preliminary results show that a noise temperature of 240 K is routinely obtained at around 600 GHz. The best double-side-band receiver noise temperature measured so far is 161 K at 597 GHz. The achieved RF bandwidth is only about 5 % and the center frequency of the resonance is also shifted towards lower end of the target frequencies.