Nature-Inspired Frequency Selective Surface in Fibonacci Spiral with Closely Resonant Bands

This paper presents a novel nature-inspired tri-band frequency selective surface (FSS) characterized by closely spaced bands, angular stability, and polarization independence. The FSS element adopts a segmented Fibonacci spiral geometry. While a single-segmented Fibonacci spiral does not inherently possess polarization independence, the proposed proof of concept achieves this by cascading the same design geometry rotated by 90° between them. Resonant frequencies of 1.63 GHz, 2.46 GHz, and 3.43 GHz are achieved, with minimal separation ratios of 1.5 from the second to the first frequency and 1.4 from the third to the second. Additionally, angular stability is confirmed up to 45°. Simulation of the FSS is conducted using HFSS software, and the simulated results are rigorously validated against experimental data, demonstrating excellent agreement.