GREENS-FUNCTIONS FOR PLANAR SOFT AND HARD SURFACES DERIVED BY ASYMPTOTIC BOUNDARY-CONDITIONS

The Green's functions for different realisations of planar soft and ha rd surfaces are developed by using the asymptotic boundary conditions and the spectral-domain approach. The geometries considered are the id eal PEC/PMC strip surface, the strip-loaded grounded dielectric slab a nd the corrugated surface. In all cases the strips and corrugations ar e straight. The asymptotic boundary conditions are valid in the limiti ng sense, when the period of the strips or corrugations approaches zer o. The Green's functions developed have poles corresponding to surface waves. These are of three types: an ordinary surface wave in the grou nded dielectric slab propagating radially out from the source; a strip wave propagating along the strips of the strip-loaded dielectric slab and also along the strips of the PEC/PMC strip surface; and surface w aves occurring due to the corrugated surface. Fulfilment of both the s oft and hard boundary conditions is discussed in both the near-and far field regions. The strip wave of the strip-loaded dielectric slab prev ents the boundary conditions in the near-field from being fulfilled, a nd is thus undesired. The other two surface waves are needed to realis e the hard boundary condition.