A compact frequency selective surface with angular stability based on the Sierpinski fractal geometry

The Sierpinski fractal geometry is used to design frequency-selective surface (FSS) band-stop filters for microwave applications. The design's main goals are FSS structure size compactness and angular stability at the resonant frequencies, as well as dual-band and dual-polarized performance. The proposed FSS structure is composed of a periodic array of fractal patch elements printed on a dielectric substrate layer. A parametric investigation of the FSS frequency response is accomplished to find out the effect of the fractal patch element's cell size and iteration-number (level). Tuning possibilities are observed at the FSS resonance bands when the fractal patch element level is increased. To validate the used methodology, three prototypes are built and measured in the frequency range from 3.0 to 14GHz. It is shown that the proposed FSS structure presents the spatial filters' most desired characteristics such as compactness, with high frequency compression factor values (up to 66.08%), dual-polarization, and excellent angular stability.