High selectivity dual-passband FSS for 5G n78/n79 bands with alternating copper-dielectric configuration

Abstract The proposed Frequency Selective Surface (FSS) with dual-passband capabilities is presented in this paper for enhanced interference mitigation in 5G n78 and n79 bands. The key contribution of this work is the development of a single-layer, alternating copper-dielectric configuration that integrates circular loops with a decagonal pattern on an FR4 substrate, enabling precise frequency selectivity and efficient suppression of out-of-band emissions. The proposed FSS achieves resonance at 3.5 GHz and 4.8 GHz with a 3 dB fractional bandwidth of approximately 3.5%. The design employs an R-T-R-T-R (reflection-transmission-reflection-transmission-reflection) mechanism, which enhances filtering performance while maintaining angular stability up to 60° for both TE and TM polarizations. Simulation and experimental results validate its robust performance. The low-profile structure, acceptable frequency ratio, and effective out-of-band suppression make it a reliable solution for 5G communication systems.