An investigation is made into the directive radiation patterns produced by an electric line source inside of a low-permittivity metamaterial slab over a ground plane. The metamaterial slab is modeled as a homogeneous slab with a plasma-like dispersive permittivity. For low values of the slab permittivity, a very directive beam pointing at broadside can be obtained. Conditions for the maximization of the power density radiated at broadside are given, and it is shown that the directive radiation effect at broadside is due to a leaky mode supported by the slab with small and nearly equal values of the phase and attenuation constants. The frequency bandwidth and the directivity at broadside are also expressed in a simple closed form in terms of the attenuation constant of this leaky wave. Finally, numerical results are obtained for an actual metamaterial slab composed of metallic rods. © 2005 IEEE.

In this work, bandwidth properties of planar leaky-wave antennas made of a grounded dielectric slab covered with a partially-reflecting surface are investigated. The partially-reflecting surface is described by an equivalent shunt susceptance. It is shown that, with respect to a constant frequency-independent susceptance, the antenna bandwidth is not reduced using a frequency-dependent model, except for very specific cases. With reference to passive lossless structures, numerical examples are provided that illustrate the attainable performance and confirm the theoretical analysis.

An investigation of planar metamaterial antennas consisting of grounded metamaterial substrates with low and/or high values of the electric permittivity and/or the magnetic permeability excited by dipole sources is presented. Their performances are characterised in terms of their capability to radiate high levels of power density in the broadside direction and to produce narrow pencil beams pointing at broadside with high directivity. To achieve a high directivity, a pair of weakly attenuated cylindrical leaky waves is excited along the metamaterial substrate; sufficient conditions are established for the existence of such leaky waves in terms of the values of the substrate permittivity and permeability. Approximate closed-form expressions are derived for the phase and attenuation constants of the leaky waves. Numerical results are given in order to illustrate the radiative features of this class of antennas and to validate the theoretical analysis. © 2007 The Institution of Engineering and Technology.