Glass Penetrating Transparent Surface with Square Loop/Cross Double-Layer FSS for Indoor Millimeter-Wave Communications

In this study, a glass penetrating transparent surface (GPTS) featuring a transparent frequency selective surface on window glass is proposed for indoor millimeter-wave communications. The proposed GPTS is characterized by a spatial filtering function and a high Q-factor for 5G (n257; 26.5–29.5 GHz). A design with a cascading structure of dielectric polyethylene terephthalate (PET) layer is applied to the GPTS, which acts as a bandpass filter for electromagnetic waves incident at angles between 0° and 45°. Furthermore, the correlation between the lumped elements and the bandwidth of the proposed GPTS structure is analyzed. In addition, another dielectric PET layer is used at the bottom of the glass to enhance the transmission response of the equivalent circuit model. Based on the measured results, it is demonstrated that the proposed GPTSs are prospective candidates for signal-selective applications on window glass.