Broadband Double-Layered Huygens’ Metasurface Lens Antenna for 5G Millimeter-Wave Systems

A double-layered Huygens' unit cell is proposed to design a broadband metasurface lens (meta-lens) for 5G millimeter-wave antennas. The Huygens' unit cell consists of a pair of antisymmetric conducting semicircle arc elements on both surfaces of a thin dielectric substrate. The surface currents flowing at the opposite directions on both conducting elements form an electric current loop to induce the orthogonal magnetic current, and then the Huygens' resonances are stimulated. The Huygens' unit cell provides the transmission phase coverage of over 400° with transmission amplitude better than -2.3 dB. This breaks through the phase shift limitation of a conventional double-layer frequency-selective surface (FSS) element. It shows that induced magnetism makes such a Huygens-based meta-lens very compact with only one printed circuit board. As an example, a double-layered meta-lens on a 1.5 mm-thick dielectric substrate is designed and experimentally verified. The meta-lens antenna achieves the measured peak gain of 30.7 dBi at 26.2 GHz with an aperture efficiency of 42.25% over the 3 dB bandwidth of 15.7% from 24.1 to 28.2 GHz, fully covering the proposed 5G spectrum from 24.25 to 27.5 GHz. This proposed method greatly helps in the application of promoting planar lightweight low-cost broadband lens antennas in the coming 5G systems.