Search

A simple analytic expression is derived from the quantum theory of mixing ignoring all reactances, which predicts that a smaller image termination conductance always increases the range of parameter values which produce infinite available gain in the superconducting quasiparticle mixer. An exactly short circuited image is anomalous in that infinite gain is strictly prohibited, except for one special case. Including the nonlinear quasiparticle reactance, the calculated gain contours for real junction I-V curves, displayed on a Smith chart of image termination impedance, are symmetrical about an axis rotated counterclockwise from the real axis. This rotation implies that the predominant effect of the nonlinear reactance is a time delay. This time delay may be related to the average time delay in the quasiparticle response function.