3.1 Introduction

The first order conditions have proved useful for simulating the properties of imperfectly conducting and coated geometries in propagation, scattering and antenna studies. Analytical and numerical solutions have been developed for a variety of configurations, and in the next two chapters we concentrate on the application of the impedance boundary and transition conditions to problems amenable to analytical solution. The coated half-plane and junction, the material half-plane and junction, and the coated wedge are particular examples of these. In this chapter we consider the analysis of half-planes and junctions that are modelled using the equivalent impedance or sheet geometries illustrated in Fig. 3-1. The accuracy of the SIBC in simulating dielectric coatings was discussed in Chapter 2, and it was pointed out that the SIBC provides a reasonable simulation for thin (particularly lossy) coatings. When in doubt, the exact reflection coefficients can be compared with those of the SIBC surface to evaluate the validity of the approximation. However, such a comparison does not account for simulation errors caused by an abrupt termination of the coating. A numerical analysis indeed demonstrates that the SIBC approximation, although sufficiently accurate far from the edge, is substantially in error within a distance of about ? ₀/10 from the edge. This is illustrated in Figs. 3-2 and 3-3 for a coated right-angled wedge and a coated half-plane. The coating thickness in these figures is 0.06 ? ₀ and the incidence angle is 135 from the top face. The impedance calculations were...