High-efficiency reflectarray antenna using a compact focusing meta-lens

The mechanisms of achieving high phase efficiency of a meta-surface are researched and analyzed systematically. For a reflective element, an electrically small size, a complete phase-shift range of more than 360°, and also a smooth phase response play an essential role in determining the high phase efficiency. Based on the design principle, an excellent element is proposed consisting of an isotropic three-turn square-ring resonator (ITSR) on a single-layer slab. The characterizations of the ITSR element are investigated in depth through theoretical calculation, comparative analysis, and electromagnetic (EM) simulation. A focusing meta-lens, with a parabolic phase distribution, is well optimized using 14 × 14 elements. Good focusing effect is demonstrated within a wide bandwidth of more than 1 GHz. Exciting the meta-lens with a waveguide feed antenna at the focus, a high-efficiency reflectarray antenna is designed, which shows a series of advances, such as high aperture efficiency of better than 70%, 1-dB gain bandwidth wider than 13.07%, and also competitive radiation gain. The proposed strategy opens an avenue to new types of high-efficiency RMSs and reflectarray antennas with enhanced radiation characteristics.