Accelerating the CBFM solution of 3D electromagnetic scattering by using MLFMA and ACA

The characteristic basis function method (CBFM) is a kind of direct method for solving EM scattering and radiation problems based on integral equation (IE), the number of unknowns could be dramatically reduced through building CBFs over sub-domains, final matrix equation can be solved by direct method, so it is especially suitable for multiple excitation case. But the filling time of matrix entries is very time consuming, in this paper, MLFMA is used to speed up the filling of the reduced matrix. Further, the Adaptive Cross Approximation algorithm (ACA) is applied to speed up the filling of the impedance entries of the extended blocks required in CBFM. Two typical results are shown to demonstrate the efficiency of this present method finally.