Electromagnetic boundary and its realization with anisotropic metamaterial.

A set of boundary conditions requiring vanishing of the normal components of the D and B vectors at the boundary surface is introduced and labeled as that of DB boundary. Basic properties of the DB boundary are studied in this paper. Reflection of an arbitrary plane wave, incident with a complex propagation vector, is analyzed for the planar DB boundary. It is shown that waves polarized transverse electric (TE) and transverse magnetic (TM) with respect to the normal of the boundary are reflected as from respective perfect electric conductor and perfect magnetic conductor planes. The basic problem of current source above the planar DB boundary is solved by applying TE and TM decomposition for the source. Realization of the DB boundary in terms of an interface of uniaxially anisotropic metamaterial half-space with zero axial medium parameters is considered. It is also shown that such a medium with small axial parameters acts as a spatial filter for waves incident at the interface which could be used for narrowing the beam of a directive antenna. Application of DB boundary as an isotropic soft surface with low interaction between antenna apertures also appears possible.