AgCl based Optically Transparent and Flexible Beam Forming Reflectarray for Millimeter-Wave Applications

This paper presents the design, fabrication, and experimental validation of an optically transparent 1-bit passive reflectarray for millimeter-wave beamforming applications. The proposed metasurface employs silver chloride (AgCl) patterning on a polyethylene terephthalate (PET) substrate, offering both high electromagnetic performance and optical transparency suitable for integration on glass or display panels. Two patch dimensions are optimized to realize a 180° reflection-phase contrast at the design frequency of 25 GHz, enabling binary phase modulation without active bias circuitry. A 32×32 array is synthesized using array factor equations to produce form beams at 20° and 30°, followed by full-wave array simulation and physical prototyping. The fabricated structure demonstrates good agreement between simulated and measured results. The proposed design achieves a lightweight, low-cost, and fabrication-friendly solution for passive beam steering while maintaining optical transparency, making it a promising candidate for smart window, vehicular radar, and indoor 6G communication applications.