A Novel Fractal Inspired Iterated Four-Legged Loaded Loop Elements Based 2.5-D Miniaturized Frequency Selective Surface

This letter presents a 2.5-D frequency selective surface (FSS) based on four-legged loaded loop elements of third-order iteration inspired by fractal geometries. This FSS design strives to harness the efficacy of the space-filling property of fractals and an additional degree of freedom associated with the use of metal vias in planar structures to obtain a miniaturized unit cell by enhancing the electrical length altogether. The proposed FSS provides a band-stop response with resonance at 1.056 GHz and demonstrates identical transmission curves for transverse-electric and transverse-magnetic modes of polarization of the incident wave. The unit cell of the proposed FSS achieves a figure-of-merit ({{{\rm{\lambda }}_{0}}/{\rm{P}}{\boldsymbol{\ }}}){\rm{\ = \ 29}}, where {{\rm{\lambda }}_{0}} is the free space resonant wavelength and P is the periodicity exhibited by the unit cell, and offers an excellent angular stability up to 75° for oblique incidence. The measured results advocate the real-time shielding effectiveness of the fabricated prototype.