Quasioptical SIS mixer with broadband integrated tuning elements

The authors have designed and tested a quasioptical superconducting tunnel junction (superconductor-insulator-superconductor, or SIS) mixer with integrated tuning elements. The designs consists of a self-complementary log-periodic antenna, the SIS tunnel junction, and the broadband superconducting tuning circuit. The tuning circuit is placed between the SIS junction and the center of the antenna. Tuning circuits are designed for 98 GHz and 492 GHz. Self-induced resonant steps are observed in I-V curves. Results of noise temperature measurements performed between 89 GHz and 104.4 GHz are reported. Results from the Touchstone simulation program, when run with the actual fabrication process parameters, show agreement with the experiment. Three types of measurements are presented: DC I-V curve measurement, heterodyne detection measurement, and direct detection measurement. All measurements show consistent results and they all agree with the theoretical predictions.<>