Omnidirectional radiation from a Fabry-Pérot antenna based on a metal strip grating

A Fabry-Pérot cavity antenna made of a metal strip grating over a ground plane that is excited by a horizontal electric dipole source parallel to the strips is studied. A homogenized representation of the grating in terms of a spatially-dispersive equivalent susceptance shows that the wavenumber of the modes supported by the structure is independent of the direction of propagation. This in turn implies that radiation patterns with high omnidirectionality may be obtained, either in the form of broadside pencil beams or conical scanned beams, through the excitation of a single leaky mode that is TM with respect to the strip direction, in contrast to other leaky wave antennas where both TE and TM modes are excited. Full-wave simulations performed with the method of moments confirm such attractive features of the antenna.