Full-Field/Scattered-Field Formulation Containing a Dielectric Interface

ABSTRACT

The usual full-field/scattered-field formulation is generalized to include a planar dielectric interface passing through the space. In this case, the source condition surrounding the central full-field region emits and captures waves consistent with scattering from a planar dielectric interface. Thus the wave in the outer scattered-field region represents just the part of the scattered wave that is due to non-planar dielectric or conductor geometry. The formulation is exact to machine precision, regardless of wavelength being smaller or larger than the simulation domain, and includes the exact second-order correction to the nominal scattering coefficients due to finite-difference truncation error. The method works even in the case of total internal reflection at the dielectric interface, that is, with the transmitted side exhibiting exponential decay rather than a propagating wave. A simple variation allows the dielectric to be a plasma, with correct scattering, regardless of whether the plasma is under-dense or over-dense. Possible applications for this facility range from RCS-type computations at hydrological or atmospheric interfaces, to geometry characterization or damage assessment of surfaces, to general boundary conditions for simulations of intermediate size EM phenomenon, e.g., L ∼ λ, to finally, an algorithm test-bed for the subject of cut-cell dielectric in the finite-difference representation.