Implementation of the impedance boundary condition in the triangular-patch scattering code for thin scatterers

The impedance boundary condition (IBC) has been previously implemented in a version of the triangular-patch code for modeling electromagnetic scattering from arbitrarily shaped bodies. This implementation, however, employs only direct numerical integration in the evaluation of the IBC contributions to the matrix elements. For very thin objects. direct numerical evaluation of the IBC contributions may be inadequate due to the singular nature of the interactions between currents on the two adjacent faces of the thin object. The authors develop a singularity extraction procedure for the IBC integrals which permits accurate computation of the source integral for observation points arbitrarily close to the source region. To test the procedures developed for very thin objects, tapered-edge and box-edge models for a 0.5 m square plate with small but finite thickness were employed.<>