Robust Large-Scale Coupling Matrix Reconfiguration via Approximate Cayley Transform

This letter proposes an optimization method based on the Cayley transform to solve large-scale filter coupling matrix (CM) reconfiguration problems. The method can significantly improve computational efficiency and initial guess robustness for high-order filter problems. Especially, for multiport filters, a two-stage optimization strategy is designed to further improve robustness, which can also be applied to other methods based on orthogonality constraints. Numerical experiments demonstrate the new method’s advantages over existing approaches.