High-frequency diffraction contribution by planar metallic - DNG metamaterial junctions

The plane wave diffraction by a planar structure formed by a thick flat metal and a lossy double negative metamaterial slab is addressed in this paper. A high-frequency domain solution is presented as linear combination of the two slab contributions. With reference to the metamaterial slab, the knowledge of the reflection and transmission coefficients allows one to evaluate the electric and magnetic equivalent physical optics surface currents that are used as sources in the radiation integral. An analytical procedure provides the uniform asymptotic physical optics diffraction coefficients containing the transition function of the uniform theory of diffraction and the reflection and transmission coefficients. A similar approach is adopted also for the contribution of the metallic slab. The resulting diffracted field is able to compensate the discontinuities of the geometrical optics field.