This work presents a fractal design methodology for frequency selective surfaces (FSSs) with Peano pre‐fractal patch elements. The proposed FSS structures are composed of periodic arrays of metallic patches printed on a single‐layer fibreglass dielectric. The shapes presented by pre‐fractal patches allow one to design compact FSSs that behave like dual‐polarised band‐stop spatial filters. On the other side, the space‐filling and self‐similarity properties of Peano fractals became possible various configurations for patch elements. An FSS parametric analysis is performed in terms of the fractal iteration‐number and cell‐size of pre‐fractal patches. To validate the used methodology four FSS prototypes are built and tested in the range from 1.0 to 13.5 GHz. Experimental characterisation of the FSS prototypes is accomplished through three different measurement setups with commercial horns and circular monopole microstrip antennas. Results show that the proposed FSS presents most of the desired features for spatial filters: compact design, multiband responses, dual‐polarisation, excellent angular stability and facility for reconfiguration.

In the last few years, bio-inspired solutions have attracted the attention of the scientific community. Several world-renowned institutions have sponsored and created laboratories in order to understand the forms, functions and behavior of living organisms. Some methods can be highlighted in the search for geometric representation of the shapes found in the nature, the fractal geometry, the polar geometry, and the superformula of Gielis. This chapter is focusing on bio-inspired microstrip antennas, especially on leafshaped antennas from the Gielis superformula that open a vast research field for more compact antennas with low visual impact.

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This paper presents a design methodology for frequency selective surfaces (FSSs) using metallic patches with dissimilar Sierpinski fractal elements. The transmission properties of the spatial filters are investigated for FSS structures composed of two alternately integrated dissimilar Sierpinski fractal elements, corresponding to fractal levels = 1, 2, and 3. Two FSS prototypes are fabricated and measured in the range from 2 to 12 GHz to validate the proposed fractal designs. The FSSs with dissimilar Sierpinski fractal patch elements are printed on RT/Duroid 6202 high frequency laminate. The experimental characterization of the FSS prototypes is accomplished through two different measurement setups composed of commercial horns and elliptical monopole microstrip antennas. The obtained results confirm the compactness and multiband performance of the proposed FSS geometries, caused by the integration of dissimilar fractal element. In addition, the proposed FSSs exhibited frequency tuning ability on the multiband frequency responses. Agreement between simulated and measured results is reported.

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