A novel subwavelength fractal frequency selective surface based on antenna-filter-antenna

In this paper, a novel multilayer frequency selective surface (FSS) with fractal structures is designed using subwavelength element based on the antenna-filter-antenna (AFA) concept. The upper fractal patches are inductive and non-resonant, and the fractal slots on the ground provide a capacitance. The thin substrate is equivalent to a transformer and a resonant frequency is formed. The cell periods along x and y directions are the same and the total height is the 8mm (λ / 3.75 at center operating frequency 10 GHz). Moreover, the fractional bandwidth reaches 30%. To well analyze and understand the operating mechanism of the FSS, the equivalent circuit model is proposed to analyze the transmission and reflection characteristics. The results of the simulation agree well with the results of the synthesis.