An Efficient MLFMA Solution of Self-Dual Integral Equation for EM Analysis of Multiscale IBC Objects

A fast and efficient method is proposed to analyze electromagnetic (EM) scattering of multiscale objects with impedance boundary condition (IBC). The self-dual integral equation (SDIE) in combination with the mixed-potential (MiP) multilevel fast multipole algorithm (MLFMA) is used to calculate EM scattering from the IBC targets, in which the incomplete-leaf (ICL) tree structure and interpolative-decomposition (InDe) based skeletonization technique is utilized to reduce excessive memory usage imposed by multiscale IBC targets meshed with large multiscale factor (MSF). A difference matrix generated from the near-field interactions by two grouping schemes is supplemented in the sparse approximate inverse (SAI) preconditioner to speed up the convergence of the iterative solvers. Numerical experiments demonstrate the effectiveness of the presented method.