Fast multipole method for scattering from 3-D pec targets situated in a half-space environment

The fast multipole method (FMM) is extended to the problem of an arbitrary, three-dimensional perfect conductor situated above or below a lossy, dielectric half space. The interactions between basis and testing functions within an FMM cluster, and for nearby clusters, are handled via the rigorous dyadic Green's function, with the latter evaluated efficiently using the complex-image technique. Intercluster interactions are modeled as in the free-space FMM, with the dyadic Green's function approximated via real images and equivalent reflection coefficients; these approximations have proven to be highly accurate. Example results are presented for a large trihedral fiducial target, in free space and above a lossy, dispersive half space, with comparisons presented between the FMM and a rigorous method-of-moments (MoM) solution.