Analysis of Nonlinearity in Step in Width Discontinuity of Superconducting Coplanar Waveguide Structures

In this paper, the nonlinearity in superconducting coplanar waveguides (SCPWs) with step in width discontinuities has been analyzed using a distributed nonlinear circuit model. In such structures, nonlinearities depend on the current distribution of the central strip of the SCPW. A numerical electromagnetics approach based on the method of moments, which analyzes high-frequency planar circuits, determines the current distribution. This is used to obtain the nonlinear circuit elements of a discontinued SCPW structure. The equivalent nonlinear circuit model can be solved using the harmonic balance method as has been done in an example of a step in width SCPW. The accuracy of the model is shown by comparison of results from an experiment for a SCPW transmission-line structure. Moreover, all different types of step discontinuities in a SCPW have been compared and the efficient structure, which has the minimum nonlinearity has been defined.