A Triple Band Frequency Selective Surface with Low Insertion Loss, Angular Stability and Polarization Independence

This paper presents the design and experimental validation of a compact, single-layer, triple-band Frequency Selective Surface (FSS) based on triple square loops. The proposed structure targets resonant frequencies at 1.56 GHz, 2.45 GHz, and 3.50 GHz, corresponding to the GPS L1, Wi-Fi, and 5G bands, respectively. An equivalent circuit model (ECM) was developed to guide the initial parametric design, reducing reliance on computationally intensive full-wave simulations. The structure was optimized using HFSS and fabricated on a low-cost FR-4 substrate. Simulated and measured results show good agreement, with three well-defined stop bands exhibiting low insertion loss and stable resonant frequencies. Experimental measurements under oblique incidence up to 45° confirm the angular stability of the design for both TE and TM polarizations. Compared to prior works, the proposed FSS offers simpler geometry, lower fabrication complexity, closely spaced resonances with minimal frequency shift under angular variation, and low pass-band insertion losses. These features make the proposed FSS a strong candidate for compact and low-profile solutions in GPS, Wi-Fi, and 5G systems requiring multiband electromagnetic filtering.