Studies of Josephson Mixing in SIS Junctions

Integrated receiving structure comprising self-Babinet-complementary spiral antenna and two SIS junctions connected in series via two matching microstrip structures has been designed, fabricated and experimentally studied. The calculated microwave responsp for such receiving structure has two maxima at 450 and 900 GHz. Direct detector response of such receiving structures has been measured using Fourier Transform Spectrometer in the frequency range 0.1 ¿1 THz. Microwave mixer performance has been measured with 500 GHz band LO source. The Josephson conversion with noise temperature of about 100 K was observed in the vicinity of the first Shapiro step at about 0.95 mV corresponding to 475 GHz signal frequency and with noise temperature 360 K near the second step at 1.8 mV corresponding to 900 GHz signal frequency. To prove that it was correct frequency down conversion the additional experiment was performed at first Shapiro step using the 4-th harmonic of Gunn oscillator 4×120 GHz instead of hot/cold load signal source.