Wave Scattering by Dielectric and Lossy Materials Using the Modified Equivalent Current Approximation (MECA)

An approximation is presented for the calculation of the equivalent currents based on the oblique incidence of a plane wave on the interface between free space and lossy dielectric media. The Snell reflection coefficients establish the relation between incident and reflected waves, then, the boundary conditions establish the equivalent electric/magnetic currents in the free space region using the total magnetic/electric fields. The interface is discretized into planar triangular facets, on which currents are assumed to have constant amplitude and linear phase variation in order to analytically calculate the scattered fields. Our modified equivalent current approximation (MECA) reduces to the well-studied physical optics (PO) formulation in case of PEC surfaces. Simulations to validate the formulation are performed over electrically large canonical geometries - a lossy dielectric sphere, a rough plate and a right dihedral - to compare the calculated Radar cross section (RCS). Good agreement between MECA and analytical/method of moments (MoM) results is demonstrated.