Analysis and optimization of intermodulation in high-Tc superconducting microwave filter design

The authors present a numerically efficient way to determine the intermodulation power arising in a weakly nonlinear N-resonator high-T-c superconducting microwave filter. This is used to analyze a given filter configuration in order to locate the resonators which are contributing most to the intermodulation power and give a means for reducing intermodulation. Using simulated annealing, the different parameters of a filter are optimized in order to reduce intermodulation within given constraints on the shape of the linear filter response. The possibilities of these methods are discussed. Calculations of this kind are useful in high-T-c microwave filter design, where nonlinearities can pose a problem.