Design and Implementation of Ultra-thin Wideband FSS with Sharp Sidebands using Tripole Slots

In this paper, an ultra-thin bandpass frequency-selective surface (FSS) is presented with wide passband and sharp roll-off sideband performance characteristics for X-band frequency regime. The design consists of a conventional unloaded tripole element printed on either side of a single-layered dielectric substrate. It exhibits a wide passband of 1.34 GHz (-3 dB) with better than 0.2 dB insertion loss performance at normal incidence of electromagnetic (EM) wave. The structure shows different performance in TE and TM operating modes at different incident angles because of its asymmetric unit cell shape. The operating principle is studied using equivalent circuit model (ECM) in conjunction with fullwave simulation and detailed parametric analysis has been performed. In addition, the thickness of reported structure is 0.027λ which is ultra-thin and hence suitable for practical application. Further, in order to avoid the breakdown of FSS elements due to high microwave powers, encapsulation of the FSS structure in thin dielectric layers is discussed.