Highly Efficient, Broadband, and Optically Transparent Reflectarrays Enhanced With Frequency Selective Surfaces and Multiresonance Subwavelength Elements

The rapid advancement of wireless communication technologies requires efficient, optically transparent devices that can support high performance while maintaining optical transparency. This paper presents an optically transparent reflectarray (RA) antenna, enhanced with frequency selective surface (FSS) and multi-resonance subwavelength elements based on fine metal lines (FMLs). FMLs, with a width of 50 μm, are utilized for both the phase shifting surface and FSS layer, contributing to high optical transparency. The thin FML based bandstop FSS serves as the RA ground, enhancing optical transparency and broadening device bandwidth. A single-layer, low-loss cyclic olefin copolymer (COC) dielectric substrate is employed to further improve the RA’s optical transparency, efficiency, and mechanical properties. To achieve broadband performance and a full 360° phase shift range, a multi-resonance subwavelength element is proposed. A phase compensation method is implemented to correct feeding phase center errors, thereby improving aperture efficiency. A 20×20-element optically transparent RA is designed as a concept demonstration, showing significant performance advantages over existing RA technologies. Additionally, the polyethylene terephthalate (PET) films with FML structures are replaceable, enabling flexible beam adjustment through the manual substitution of pre-designed films with different phase distributions. Wireless communication experiments confirm its potential and broad prospects for advanced communication systems and related application.