ANALYTICAL PREDICTION FOR THE OPTIMUM OPERATING-CONDITIONS OF SIS MIXERS

Using Tucker's quantum theory of mixing and a quasi five-frequency app roximation proposed by Kerr et al., this paper explores the optimum op erating conditions of SIS mixers in the frequency region of 100 to 650 GHz. Four parameters (i.e., omegaR(n)C(j) product, normal state resis tance R(n), RF source admittance (R(rf)-1+jB), and IF load resistance R(if)) affecting the performance of an SIS mixer have been investigate d. Our results indicate that, independent of the absolute value of R(n ), the SIS mixer performance is dominated by R(rf)/R(n) and R(if)/R(n) ; and that the mixer performance becomes quite insensitive to the omeg aR(n)C(j) product, as the mixer operating frequency goes up to submill imeter wavelengths. Concerning all properties of an SIS mixer, the opt imum R(rf)/R(n) value seems proportional to f(l/n) (n almost-equal-to 2), and the optimum R(if)/R(n) and jB/G(n) values are relatively indep endent of frequency, about 0.5 to 1.5 and -j0.5 to -j1.0 respectively.