Fast fourier transform accelerated multilevel Green's function interpolation for mixed potential and direct field surface integral equations

For the solution of electromagnetic surface integral equation problems, a fast solver based on multilevel interpolation of the respective Green's functions is presented. Besides the commonly used electric current mixed-potential integral equation formulation (MPIE) of the electric field integral equation (EFIE), the effectiveness of a direct field formulation for very ill-conditioned low-frequency problems is shown. The superior efficiency of the presented algorithm is proved by several numerical examples.