Contents I. Introduction
Frequency selective surfaces (FSSs) are the surfaces which can shift through specific frequencies and can likewise let the necessary frequency to go through it for which it is planned. FSS pass or obstruct the desired or undesired EM waves in free space and thus most popularly act as spatial filters. Recently FSS gained high research attention due to its potential uses in cloaking [1], electromagnetic shielding [2], absorbers [3], radome [4], antenna radiation enhancement [5]–[8] etc. A novel stop band single layered FSS that offers wide band response of 7.5 – 11.5 GHz is proposed in [9]. The unit cell of FSS consists of four patches triangular in size enclosed in a square loop. K. Katoch et al. proposed a triple band notched Ultra-wide Band (UWB) FSS [10] which has dual square split ring resonator (SSRR) on top layer and a square loop structure on bottom layer to offer three notches at Wi-MAX, WLAN and X-Band in the UWB frequency range. H. Li, et al. proposed an active FSS in [11], having unit cell dimension of to cover 3.7-6.8 GHz bandwidth. A compact FSS with Y-type elements was proposed in [12], The FSS was designed to operate at 3–8 GHz band. It consists of a single metal layer with slots on F4B substrate. D. Sharma and T. Shanmuganantham, proposed a multi-band FSS in [13] which was fed using a micro-strip line. The FSS formed by a rectangular U-shaped Patch on FR4 substrate to find application in GSM band. In [14], a dual layered FSS was proposed that provides pass band from 3.3 to 10.5 GHz. Compact dual layered FSS were proposed in [15] that covers wideband from 3 to more than 10 GHz. A three metallic layered and two substrates layered FSS with transmission poles at 3 and 3.5 GHz is proposed in [16]. A uniplanar FSS of 11×11 mm2 was proposed in [17] that offers wideband from 0.001 to more than 17 GHz. However, all these reported FSS [6]–[20] lack in the compactness while aiming the wideband coverages.
