High-gain omnidirectional radiation patterns from a metal strip grating leaky wave antenna

Recently, the possibility to achieve highly directive radiation from simple sources embedded in grounded slabs made of artificial materials has been investigated and related to the excitation of leaky waves. Furthermore, the radiation of almost-omnidirectional pencil beams pointing at broadside or conical beams scanned off broadside has been reported for a grounded wire-medium slab excited by a dipole source. This has been explained in terms of the excitation of a cylindrical leaky wave having isotropic propagation features as a consequence of the spatial dispersion of the homogenized medium. In this work we aim at showing that highly directive but nearly omnidirectional beams are obtained by employing a grounded slab made of an ordinary homogeneous material (air is used here) covered with a MSG and excited by a horizontal electric dipole source. An approximate homogenized network representation of the MSG, which takes into account its spatially dispersive nature, allows us to analytically prove that the wavenumber of the dominant leaky wave is independent of the azimuthal propagation angle. As a result, the radiated beam is almost omnidirectional, as confirmed by rigorous simulations of the actual periodic structure performed with the method of moments.