Single-Layer Frequency-Selective Surface on Window Glass for 5G Indoor Communications

This letter introduces a novel transparent single-layer frequency-selective surface (FSS) design on conventional window glass, which is aimed at achieving signal selectivity for 5G millimeter-wave communication (n257; 26.5-29.5 GHz). The unit cell of the FSS layer features a structure formed by square loops and spirals using small-width metal lines (200 and 250 μm). Additionally, a new approach is presented to enhance the transmission characteristics of the FSS layer by integrating a transparent dielectric slab while maintaining good optical transparency (>60%) in the visible light spectrum. The measurement results validate both the theoretical predictions and the design procedure, confirming the feasibility and transparency of signal filtering on window glass at millimeter waves. These findings hold promising potential for optimizing 5G wireless communication systems and simplifying signal filtering applications.