A Flat-Top Beam Generator Based on Triple-Layered Metal-Only Metasurface

A flat-top beam generator based on a metal-only metasurface is designed in this paper. The proposed element consists of three metallic layers separated by two air spacers, where each layer features an identical pattern-an I-shaped curved bar etched from a metal plate-with a 45° mutual rotation between adjacent layers. Leveraging the intrinsic polarization conversion property, the amplitude and phase modulation of the crosspolarized transmission wave are achieved by rotating and resizing the I-shaped curved bar, respectively. A global optimization algorithm, Genetic Algorithm (GA), is employed to achieve the desired amplitude and phase distributions for flat-top beam generation. Simulation results demonstrate the successful generation of a flat-top beam with a 3-dB beamwidth of 50° at 9.5 GHz, showcasing the design's suitability for electromagnetic environmental effects test of high-power microwave.