Compact ultra-wideband multi-band frequency-selective surface with angular stability using CNN–GNN-assisted design optimization for 5G applications

This work presents a novel compact frequency-selective surface (FSS) exhibiting ultra-wideband (UWB) band-stop features, excellent angular stability, and polarization insensitivity for advanced electromagnetic shielding and antenna enhancement applications. The suggested FSS consists of cross-dipole and meandering convoluted elements etched on a compact FR-4 substrate with a unit-cell size of 0.0308λo × 0.0308λo, achieving one of the most compact designs reported in literature. The CST Microwave Studio demonstrates a wide stop-band response from 1.2 to 10.69 GHz at −10 dB reference level, covering the entire UWB spectrum with fractional bandwidth exceeding 99%. The structure exhibits angular stability up to 80° for both TE and TM modes, enabling robust operation under oblique incidence. Experimental validation using a 45×45 prototype shows excellent agreement with simulation results. This design is miniaturized to a greater degree than existing state-of-the-art FSS designs, wider rejection bandwidth, and improved angle/polarization tolerance. This research provides a scalable, fabrication-friendly solution for radome design, EMI/EMC compliance, wireless communication shielding, and antenna pattern control, enabling next-generation UWB systems.