Low-Profile Dual-Band Dual-Polarized Aperture-Shared Antenna Array Using Bifunctional Metasurface

This article presents a novel dual-band aperture-shared base-station antenna array using a bifunctional metasurface to simultaneously realize broadband cross-band decoupling and low profile. The proposed array has a lower band (LB) slot antenna and four higher band (HB) dipole antennas. The HB stopband suppression of the LB antenna is achieved by loading dumbbell-shaped slots on the full-wavelength radiating slot, and the cross-band coupling is reduced. Four wideband HB antennas are stacked above the LB antenna, sharing the same ground plane with the LB antenna. The proposed bifunctional metasurface is placed below the LB antenna. It functions as an artificial magnetic conductor surface in the LB, and reflects the LB electromagnetic (EM) wave in a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.089\lambda _{\text {L}}$ </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">$\lambda _{\text {L}}$ </tex-math></inline-formula> is the lowest frequency free-space wavelength). The metasurface can absorb the HB scattering wave from the LB antenna. The cross-band interference of the LB antenna to the HB antenna is reduced. Therefore, the HB antenna radiation pattern is restored well, and the cross-band isolation is enhanced to be over 30 dB across the whole operating bandwidth. Measured results indicate that the proposed array can maintain stable radiation with ±45° dual polarization in the band of 0.67–0.98 GHz (37.6%) and 2.48–5.2 GHz (70.8%).