Abstract
Radiation features are studied for a grounded wire-medium slab excited by a simple canonical source, i.e., a horizontal electric dipole. For the first time, an approximate analysis based on a homogenized model for the wire medium as well as a rigorous full-wave analysis of the actual periodic structure are presented. The homogeneous model takes into account both anisotropy and spatial dispersion of the metamaterial medium in the long-wavelength regime. One rather surprising result is that this structure allows for directive pencil beams at broadside that are azimuthally symmetric (in spite of the directionality of the wires). The structure also allows for conical beams that point at a chosen scan angle, where the beam angle and beamwidth are azimuthally independent, and the beam peak in the elevation planes remains approximately constant during the scanning process, in contrast with other types of planar leaky-wave antennas. These remarkable features are explained in terms of the azimuthal independence of the wavenumber for the leaky mode that is responsible for the beam.
Highlights
First pointed out in [16], is that even for large wavelengths the electric response of the wire medium is non-local; a homogeneous model has to take into account its anisotropy and its spatial dispersion, through a dyadic permittivity that explicitly depends on the spatial wavenumbers when expressed in the spectral domain
In this paper the radiation from a dipole source embedded in a grounded wire-medium slab has been studied, with both a homogeneous model and a fullwave analysis of the actual structure via a periodic method-ofmoments procedure
The surprising characteristic of omnidirectional directive radiation is shown here for the first time and is interpreted in terms of a leaky mode supported by the structure
Summary
THE possibility to achieve directive radiation from simple sources by employing planar layered structures made of artificial materials has been studied by several research groups, from the early investigations by Gupta and Bahl [1], [2] on slabs hosting periodic layers of metal wires (wire-medium slabs) to the more recent ones stimulated by the advent of electronomagnetic bandgap materials and metamaterials [3]–[12]. We extend the analysis of [10] by considering a grounded wire-medium slab excited by an elemental horizontal electric dipole parallel to the wire axis (see Fig. 1) In this case the problem is 3D, the excited field is not purely. Show various peculiar and interesting features, such as the possibility to achieve narrow omnidirectional beams at broadside, as well as conical scanned beams with equal beam angles and beamwidths in all azimuthal planes These results are validated by full-wave simulations of the actual periodic metamaterial structure, performed with a method-of-moments approach that suitably exploits the translational symmetry of the structure along the wire axis in order to reduce the 2.5D problem of plane-wave incidence at oblique angles to a purely 2D problem corresponding to normal incidence.
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