Mixing efficiency of SIS junctions

To evaluate new SIS technologies as low noise mixers we have investigated theoretically the frequency down-conversion efficiency of SIS junctions with IV curves which closely resemble experimentally observed curves. Leakage current and IV curve "sharpness" of the current rise at are included as parameters. We have applied a 3-port version of the quantum mixing theory to study the importance of these parameters on conversion efficiency. The results suggest that the leakage conductance should be less than 10% of the normal conductance, that the voltage width of the current rise should be less than 10% of the gap voltage, and that the optimum frequency of operation is near 10% of the gap frequency, .