Nonlinear modelling of superconducting devices and circuits

Recent progress in the development of techniques for fabricating high-quality superconducting components, together with major advances in the theoretical understanding of quantum detection and mixing at millimetre and submillimetre wavelengths, have made the development of CAD tools for superconducting nonlinear circuits an important and exciting challenge. As a first step towards developing general purpose CAD techniques, the authors have devised algorithms, and written, in the C programming language, modular software for analysing the large-signal, small-signal and noise behaviour of quasiparticle tunnel-junction circuits. At present, they are using the software to study the complex behaviour of SIS mixers, however, the software can also be used for studying other modes of operation, and other tunnelling structures for which macroscopic quantum effects are important