Modelling of current distribution and nonlinearity in superconducting coplanar waveguide (CPW) transmission line

Abstract

There are nonlinear behaviours such as harmonic generation and intermodulation distortion (IMD) in superconductive circuits especially at low temperatures. In this paper, current distribution in superconducting coplanar waveguide transmission line (CPWTL) was modelled. After that, nonlinear circuit model to predict nonlinear behaviours in superconducting CPWTLs was proposed. Current distribution in superconducting CPWTL geometry with finite ground planes was formulated using of numerical method based on 3D-FEM. These formulations can be used to obtain accurate closed-form expressions for nonlinear components in distributed circuit model based on considering both quadratic and modulus nonlinear dependence on current. This model was analysed nonlinearly using Harmonic Balance method as a nonlinear solver. The proposed model can be used to predict nonlinear behaviours such as IMD and harmonic generation in superconducting CPWTL in different input powers and different temperatures. There are good agreement between nonlinear results from our proposed model and measured ones.