J. Phys. IV France
Volume 12, Numéro 3, May 2002
Page(s) 165 - 168

J. Phys. IV France
12 (2002) Pr3-165
DOI: 10.1051/jp420020060

Non-linear two-frequency analysis of SIS mixers through harmonic balance

S. Withington, P. Kittara and G. Yassin

Department of Physics, Cavendish Laboratory, Madingley Road, Cambridge, U.K.

We present a numerical procedure for simulating the non-linear behaviour of Superconductor-InsulatorSuperconductor (SIS) tunnel junction mixers. Mixers of this kind are used extensively in high-performance submillimetre-wave astronomical receivers. The procedure is complete in that both the signal and local-oscillator voltages can be at high levels, with significant amounts of harmonic content; also, the full quantum mechanical behaviour of the tunnel junction is taken into account. The initial simulations show that multi-tone analysis can be carried out in a numerically efficient manner, and that saturation, and the attendant generation of IF harmonics, can be modelled rigorously. This work constitutes the first full non-linear model of an SIS mixer, and the theoretical and numerical procedures described, will be of great importance when designing the next generation of heterodyne astronomical receivers.

© EDP Sciences 2002