X-Shape Sierpinski fractal antenna with reduced slot count for dual-band 5G-V2X and X-Band vehicular applications

This paper presents a modified X-shaped Sierpinski fractal antenna that supports Sub-6 GHz 5 G-vehicle-to-everything communication and X-band short-range vehicular sensing. However, achieving both bands in a single compact element is challenging due to high fabrication complexity, impedance‑matching difficulties at Sub-6 GHz and X-band, and performance degradation under vehicular roof mounting. This requirement is addressed through a selective diagonal iteration strategy applied exclusively to the four diagonally positioned sub-squares of the Sierpinski carpet. This modification reduces the total slot count from 73 to 21, a 71% reduction compared to the standard third-iteration design and improves fabrication repeatability while preserving dual-band resonance behavior. The proposed design integrates vertical shorting pins for independent Sub-6 GHz resonance tuning and a defected ground structure for X-band impedance optimization, fabricated on a low-cost FR4 substrate within a compact 32×32×1.6 mm3 footprint (0.63λ0×0.63λ0 at 5.9 GHz). Experimental validation demonstrates impedance bandwidths of 5.88–6.25 GHz (S11=−28.80 dB) and 8.63–9.65 GHz (S11=−14.00 dB), with measured gain values of 4.50 dBi and 6.30 dBi, respectively. The integration of vehicle roofs has been validated across six ground plane dimensions, ranging from 100×50 mm2 to 600×300 mm2.