Nested Equivalence Source Approximation for Multiscale and Penetrable Medium Simulations

In this paper, we will review the further research on our proposed NESA (Nested Equivalence Source Approximation) as a low-rank method for MoM (method of moments) for realistic multiscale and penetrable medium simulations. For the low-frequency problem, the equivalent sources are placed uniformly in the closed spherical shell space surrounding the original discrete region with linear complexity. For the high-frequency problem, the space is evenly divided into six regions according to six directions, and the equivalent sources are evenly placed in each region with O(NlogN complexity, where N is the number of unknowns. We apply NESA to simulate some real models and calculate Surface Enhanced Raman Scattering (SERS) enhancement factor under different materials. The numerical results demonstrate the validity of the proposed method.