Directive leaky-wave radiation from a dipole source in a wire-medium slab

Radiation features are studied for a grounded wire-medium slab excited by a simple canonical source, i.e., a horizontal electric dipole. For the first time, an approximate analysis based on a homogenized model for the wire medium as we as a rigorous full-wave analysis of the actual periodic structure are presented. The homogeneous model takes into account both anisotropy and spatial dispersion of the metamaterial medium in the long-wavelength regime. One rather surprising result is that this structure allows for directive pencil beams at broadside that are azimuthally symmetric (in spite of the directionality of the wires). The structure also allows for conical beams that point at a chosen scan angle, where the beam angle and beamwidth are azimuthally independent, and the beam peak in the elevation planes remains approximately constant during the scanning process, in contrast with other types of planar leaky-wave antennas. These remarkable features are explained in terms of the azimuthal independence of the wavenumber for the leaky mode that is responsible for the beam.