This paper presents a novel type of basis functions, whose spectral-and space-domain properties can be exploited for the efficient method of moments (MoM) analysis of planar metasurface (MTS) antennas. The effect of the homogenized MTS is introduced in the integral equation as an impedance boundary condition (IBC). The proposed basis functions are shaped as Gaussian-type rings with small width and linear azimuthal phase. The analytical form of the spectrum of the Gaussian ring basis allows for a closed-form evaluation of the MoM impedance matrix's entries. Moreover, these basis functions account for the global evolution of the surface current density in an effective manner, reducing the size of the MoM system of equations with respect to the case of sub-domain basis functions. These features allow one to carry out a direct solution for problems with a diameter of up to 15 wavelengths in less than one minute using a conventional laptop. The applicability on practical antennas has been tested through the full-wave analysis of MTS antennas implemented with small printed elements.Index Terms-basis functions, leaky-wave antennas, metasurfaces, method of moments, spectral-domain approach.0018-926X (c)
In metasurface (MTS) antennas, a surface-wave (SW) is gradually transformed into a leaky-wave (LW), owing to the SW interaction with a reactance tensor periodically modulated in the aperture plane. In such antennas, the modulated reactance is typically obtained by sub-wavelength patches printed on a dielectric substrate. As an alternative technology, we propose the use of a class of metal-only MTSs in the synthesis of the reactance tensor. The absence of dielectric is useful to withstand harsh environments in space applications. The proposed element consists of a metallic cylinder with elliptical cross-section, placed on a ground plane and arranged in a square lattice with subwavelength unit-cells. This structure is well suited for fabrication by metal additive manufacturing. We have applied the metal cylinders in the design of a right-handed circularly polarized (RHCP) antenna, with broadside pencil beam at Ka band. The obtained performance has been verified by full-wave simulations. A prototype has been successfully manufactured and measured, showing a good performance.
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