High directivity at broadside with new radiators made of dielectric EBG materials

In this paper, two different kinds of EBG materials are considered that support slowly attenuating, very fast, leaky waves, such that they produce a narrow beam at broadside. Here, the EBG material is not used as a cover of a Fabry-Perot cavity, as in B. Temelkuaran et al. (2000) and A.L. Feherembach et al. (2001), but it is the EBG material itself that supports the excited leaky wave. The two proposed structures are planar and they are excited by a transverse elementary dipole, though other excitations like slots in the ground plane would lead to the same conclusions. The EBGs are made of only a dielectric material layer over a ground plane, though the same radiation performances could be achieved also without the ground plane in case an all-dielectric structure is required. The proposed designs may lead to the following advantages: they can be made of only dielectric materials and they can be used at frequencies where metals have not negligible losses; they are planar and easy to build; they are excited by a single source so no complicated feeding network has to be designed; with a proper design very high directivity can be achieved, usually with the drawback of reduced frequency bandwidth