Leaky modes on a grounded wire-medium slab

Leaky modes supported by a grounded wiremedium slab are studied here in detail for the first time. Such leaky modes are responsible for highly-directive radiation when the structure is excited by a dipole source. The analysis is carried out by means of a rigorous full-wave numerical approach based on the method-of-moments and also by using an approximate homogenized model. The use of a homogenized model that properly accounts for anisotropy and spatial dispersion leads to a remarkable and surprising result: the wavenumber of the leaky mode is independent of the azimuth angle of propagation on the surface. This result, which has not previously been observed in any other leaky-wave structure, allows for the creation of narrow conical beams that are azimuthally symmetric, as well as symmetric broadside beams. This conclusion is confirmed by the full-wave method-of-moments analysis. © 2007 IEEE