A Nested Iterative Solver for Substructure CMA of Composite Metallic–Dielectric Objects

A nested iterative solver for the generalized eigenvalue equation of the volume surface integral equation-based substructure is proposed for characteristic mode analysis of composite metallic–dielectric objects. The computation of matrix inversion and the associated matrix-vector multiplications during the solving phase is approximated by resolving two related linear systems using the proposed subblocks. To conserve computational resources, a twofold preconditioner, coupled with the multilevel fast multipole algorithm, is seamlessly integrated into the nested solver. The accuracy as well as the applicability is verified with numerical tests. Both the peak memory usage and execution time are reduced compared with a conventional solver.