Abstract
The metasurface lens composing of 2D periodic metallic patches on a grounded dielectric slab possesses several advantages such as being light, low-profile, compact, and also cheap to manufacture. In this paper, a Luneburg lens synthesized by a metasurface and designated for use as a surface wave antenna is proposed. Two types of unit cell will be compared, one whose surface wave modal dispersion varies significantly with the grazing direction and another that does not. In the context of being applied as surface wave antennas, it will be shown that the Luneburg lens synthesized by the latter kind of unit cell provides improved performance as compared to the former. Several aperture sub-efficiencies of the metasurface-based Luneburg-lens antenna shall be used for the characterization of the radiation. A prototype of the designed lens antenna has also been manufactured. Measurement results agree well with theoretical predictions and the efficacy of this device over a fairly wide bandwidth has been experimentally demonstrated.
Highlights
Over the recent years, considerable amount of research has been put into the study of metamaterial surfaces known as metasurfaces, which are able to support surface plasmon polaritons (SPPs) [1], being essentially traditional surface waves that propagate along the planar interface between a metal and a dielectric
We propose the use of hexagonal unit cells that possess reduced anisotropy of the surface-wave phase constant with respect to the azimuth propagation directions
This paper has addressed the apparent flaw with the traditional use of just a principal direction of anisotropic square periodic arrays in the generation of surface-wave modal dispersion attributes for subsequent use in synthesizing the various refractive indices required by any metasurface lens
Summary
Considerable amount of research has been put into the study of metamaterial surfaces known as metasurfaces, which are able to support surface plasmon polaritons (SPPs) [1], being essentially traditional surface waves that propagate along the planar interface between a metal and a dielectric. The surface-wave bending at all locations on any type of plasmonic lens should strictly be under the conditions of different incidence angles as the rays move from a region of a certain refractive index to another of a different [2,11]. This suggests an apparent flaw in the synthesis by using only one fixed principal surface-wave propagation direction for all points on the lens. A Luneburg lens has been designed with this unit cell to demonstrate the enhanced immunity of this type of unit cell
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