Low-Profile Broadband Dual-Polarization Double-Layer Metasurface Antenna for 2G/3G/LTE Cellular Base Stations

Abstract

A double-layer metasurface is proposed to realize the low profile of a broadband dual-polarized antenna for cellular base-station applications. The proposed metasurface is formed by the two layers of printed metallic patch unit cells on either substrate surface to miniaturize the metasurface size and enhance design flexibility by regulating the extent of electromagnetic coupling between the two layers. Despite the low profile of the antenna, a wideband operation is accomplished by operating the metasurface in the nonresonant region that facilitates wideband phase compensation and its truncation to a finite dimension with an additional transverse electric (TE) surface wave resonance. The guidelines for the design of the surface is derived from a comparison of unit cell structures and an approach is introduced to correlate their potential with surface susceptibility parameters. A detailed parametric study addresses the critical concern on the overall dimensions of the finite metasurface. A ±45°-polarized dipole antenna with an overall thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.15~\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the wavelength in free space at the center operating frequency) is designed as example. The measured results show a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert \le -10$ </tex-math></inline-formula> dB impedance bandwidth of 46.4% over the frequency range of 1.69–2.71 GHz with average boresight gain of 9 dBi with a ground plane of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\lambda _{0} \times 1.1\lambda _{0}$ </tex-math></inline-formula> , well covering 2G (1.71–1.92 GHz), 3G (1.88–2.17 GHz), and LTE (2.3–2.4 GHz and 2.5–2.69 GHz) bands.