A Cross-Type Multifocus Phase Compensation Method Enables Metalens Antenna Wide-Angle Beam Steering

Abstract

An artificial metalens manipulates the electromagnetic wavefront phase via deploying transmitted phase and amplitude of metasurfaces units, which exhibits excellent merits in beam steering application. The metalens with single-focus phase distribution can only compensate for the first-order Taylor expansion of the outgoing beam by modulating the wavefront phase entering the lens surface, resulting in a very limited beam scanning range, and the phase error dramatically increases with the beam steering to the large angles, which suffers serious gain degradation. We, herein, proposed a novel cross-type multifocus phase compensation method to modulate the wavefront phase and increase the proportion of transmitted phase linear term to enlarge the beam steering angle. Three-focus and five-focus lenses are implemented based on the proposed phase distribution method and extend the beam scanning angle to ±48° and ±71° with a gain degradation of only 3.8 dB, respectively. A three-focus metalens is designed by employing three-bit phase-quantized metasurface units and simulated with commercial software CST Microwave Studio. The metalens operates in the frequency range of 24.25–25.8 GHz. It is capable of steering the main beam from −48° to 48° with gain degradation of 3.8 dB. The three-focus metalens is fabricated and measured, and the experimental results match well with simulated ones, which validates the efficacy of the proposed multifocusing method. Meanwhile, the influence of amplitude and phase errors of the metasurface units on the metalens performance is analyzed to fully evaluate the metalens antenna and illustrate the robustness of the proposed method.