Augmented MLFMM for solving the electromagnetic scattering problems with fine structures

MLFMM augmented with a Green's function interpolation method is proposed to efficiently solve the electromagnetic scattering problems. One well-known shortcoming of the traditional mid-frequency MLFMM method is that the finest box size must be at least 0.25 wavelength to ensure the accuracy. However, there exists a myriad of real targets having fine structure, and it usually produces a large number of unknowns in each finest box when discretizing these targets in the MLFMM implemetation, which leads to a large mount of storage of near-field interactions. In this article, a Green's function interpolation method (MLGFIM) is proposed to attack this kind of problem, the MLGFIM can make the finest box size reduced to as small as 0.1 wavelength or even smaller, and it enables a significant reduction in memory and complexity against the MLFMM. Numerical examples are presented to validate the proposed scheme.