Numerical modeling of leaky-wave propagation in grounded wire-medium slabs

Dispersion properties are studied for leaky modes propagating along a grounded wire-medium slab. The medium is constituted by periodic layers of metal wires in air and the modes are allowed to propagate at an arbitrary angle with respect to the wire axis. Only modes TM-polarized with respect to the wire axis may exist. An homogenized model of the structure, which takes into account both anisotropy and spatial dispersion of the wire medium, shows that the wavenumber of such complex TM modes is independent of their propagation direction. This peculiar property, which has been shown to give rise to omnidirectional radiation from simple sources, crucially depends on the spatially-dispersive nature of the homogenized medium, recently described in the literature. A full-wave analysis of the actual periodic structure based on the method of moments confirms this feature, which turns out to be exact in the asymptotic limit of wavelengths large with respect to the wire spacing. Numerical results from both the approximate homogenized model and the rigorous full-wave approach are presented.