Design and experimental validation of a compact FSS-based absorber for sub-6 GHz 5G applications

In this study, a compact and cost-effective Frequency Selective Surface (FSS) unit cell absorber is proposed to mitigate electromagnetic interference in the sub-6 GHz 5G bands, specifically targeting the n77 (3.3–4.2 GHz), n78 (3.3–3.8 GHz), and n79 (4.4–5.0 GHz) frequency ranges. The absorber structure, fabricated on an FR-4 substrate, was designed through a systematic geometric optimization of patch dimensions and substrate thickness to enhance absorption performance via inductive-capacitive resonance tuning. Simulation and experimental results show strong agreement, with a maximum absorption rate of 98% at 4.2 GHz and over 80% absorption between 3.5 GHz and 4.7 GHz. The structure also demonstrates robust angular stability up to 60°, making it suitable for practical applications requiring directional reliability. Compared to existing designs, the proposed FSS absorber offers superior absorption efficiency, simpler fabrication, and enhanced angular resilience. This work contributes a practical and validated solution for targeted EMI suppression in 5G-enabled electronic systems.