Analytical distributed non-linear model for symmetric and asymmetric superconducting parallel-coupled microstrip lines

Superconducting materials are known to produce intermodulation distortion and other non-linear effects. In microstrip structures, the non-linearity depends on the current distribution on the strip which is mainly determined by the geometrical structure of the device. The current distribution in superconducting parallel-coupled microstrip lines is computed by a numerical approach based on a three-dimensional finite element method. This computed current distribution is used to produce a non-linear circuit model for parallel-coupled superconducting lines. A numerical technique based on the harmonic balance approach is used for non-linear analysis of the proposed equivalent circuit. To validate the accuracy of the proposed model, the results of analysis of hairpin resonator superconducting band pass filters are compared with measured results. This proposed technique is useful for fast and efficient non-linear analysis of the superconducting microstrip coupled lines.