Abstract
This paper deals with the design of scalar metasurface antennas capable of radiating a well-polarized beam in the far-field or near-field zones. The equivalent electric current over the metasurface is used to derive design equations to generate the desired field pattern based on the scalar impedance condition. In particular, it is shown that scalar metasurfaces can be used to generate linear and circular polarizations for a fixed pointing direction in the far field by properly changing locally the scalar impedance boundary condition. In addition, they can also be used to generate normal polarized Bessel beams in the near-field region. Several solutions are presented at 20 GHz, with different polarizations and feeders developed in the framework of a two-year research project financed by the French space agency (Centre National d’Etudes Spatiales). Measurements and full-wave results validate the proposed approach.
Highlights
M ETASURFACES are the 2-D equivalents of metamaterials [1]
The two near-field configurations presented in the previous section have been implemented using a circular panel of radius 3λ sharing the same impedance parameters as the previous antennas
The transverse propagation constant parameter of the Bessel beam has been selected as βρB = 0.6k0; the corresponding nondiffracting zone defined by (22) is given by z ≤ 4λ
Summary
M ETASURFACES are the 2-D equivalents of metamaterials [1] They consist of textured scatterers/apertures, arranged along a surface that can be, in general, the surface of a nonuniform stratified medium. Metasurfaces have been recently used in many applications like holographic antennas [2], leaky-wave (LW) antennas [3]–[5] planar lenses [6]–[8], polarization convertors [9], [10], orbital angular momentum communication [11], transformation optics [12], [13] or future mathematical operation [14] All these works are based on the pioneering results of Oliner and Hessel [15] about surface wave (SW) propagation over a sinusoidally modulated impedance. By choosing an appropriate modulated surface impedance, it is possible to control the propagation of SW along a surface or to obtain the transition from SW to LW modes in order to realize antennas [1], [16]
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