Transparent metal surfaces on glass windows enhance 5G mm-wave transmission for indoor communication

This study presents a straightforward design for a bandpass frequency selective surface (FSS) that achieves high optical transparency (OT) and enhances millimeter-wave transmission through glass windows for 5G indoor wireless communication. These FSSs, applied to glass windows and termed glass-penetrating transparent surfaces (GPTSs), are engineered with meta-surface technology to remain visually unobtrusive in environments where signal propagation control is essential. To maximize OT, a simple square-line pattern with miniaturized metal lines was employed. These square structures are cascaded to minimize the effect of the metal area on transparency, creating an FSS with a top layer of square loops and a bottom layer of grid wires separated by a transparent polymer layer. The proposed GPTSs were evaluated on two types of glass windows with low and high penetration losses. GPTS1, which features wider copper lines (100 μm), maintains good OT at 64 % and operates in the n257 and n261 frequency bands. In addition, GPTS2 employs narrower copper lines (30 μm), achieving an excellent OT of 81.4 %, and operating in the n257, n258, and n261 frequency bands. Results indicate that the proposed FSS designs hold promise as effective solutions for millimeter-wave signal filtering on glass windows.