Physical optics for the scattering analysis of dipole waves from strips on a grounded dielectric slab

This paper checks the accuracy of physical optics (PO) as applied to the scattering of dipole waves by a finite size surface which is composed of strips on a grounded dielectric slab. By using the closed form expressions of reflected waves from the surface, the PO calculation can be conducted straightforwardly. Since the reflection coefficients are obtained for a local plain wave and an infinite slab, considerable errors are expected for the dipole and the rapid curvature of the strip patterns. It is pointed out that for the straight patterns of strips, PO is applicable for the dipoles in at a distance of more than 0.5 wavelength from the surface. For the portion of the surface where the incident electric fields are perpendicular to the strips, larger errors are observed. The reason for this may be the excitation of surface waves. The accuracy of the PO is evaluated by comparing the calculation and measurement of the radiation patterns of a half-wavelength dipole antenna vertically mounted above the circular disk of strips loaded with a grounded dielectric slab as a reflector.