Complex Source Beam Method for EM Scattering From PEC Objects

This letter proposes a fast method that combines the complex-source beam (CSB) and multilevel fast multipole algorithm (MLFMA) for electromagnetic (EM) scattering problems. The CSB for the MLFMA is obtained by introducing an imaginary part for the independent variable of the spherical Hankel function in the translation operator, which makes the translation operator directional. Furthermore, a window function is introduced in the translation operator to make it more directional. A large part of the angular translation operators are then discarded with an angle threshold. Numerical examples demonstrate that the translation operator memory cost can be reduced significantly compared to the MLFMA, and more accurate results can be obtained compared to the ray-propagation multilevel fast multipole algorithm (RP-MLFMA).