A three layered low profile dodecagon shaped band stop frequency selective surface (FSS) is presented in this paper for X band rejection applications. The three layers are placed in a manner which is complement to each other. The low profile three layered FSS with unit cell dimensions on the order of 0.2λ 0 × 0.2λ 0 (at lower center frequency of 8.2 GHz) with overall thickness of three layers including air gap of 5.2 mm is presented. For experimental verification, a three layered FSS has been fabricated and measured. Simulation results show that the designed three layered FSS can provide a stopband from 8 GHz to 12.5 GHz with two transmission zeros of 8.2 GHz and 10.5 GHz with a fractional bandwidth of 45%. The complete design and equivalent circuit model (ECM) of the three layered FSS are presented in this paper.

A new miniaturized and ultra-thin non-resonant element-class of convoluted frequency selective surface (FSS) structure with reduced overall thickness is presented and empirically verified. The proposed FSS structure, which could be capable of providing a first order narrow band pass response for X band applications, is made up of three metallic layers separated from one another by two dielectric substrates. The outer layers are made up of convoluted inductive grids, and the inner layer is a nonresonant structure composed of convoluted square slot array. A first-order band pass response FSS with a centre frequency of 10.5 GHz and fast roll-off characteristics is presented. The overall element thickness of the proposed FSS is λ 56 , which is smaller than previously proposed miniaturized structures. The comparison between all patch layers with the proposed structure which is not an all patch layers is explicated in detail with its convoluting effects. The validity of this design procedure is verified with an equivalent circuit model, and a sample is fabricated and measurement done using a WR 90 waveguide setting for experimental verification.

A dual layer polarization-insensitive frequency selective surface (FSS) with ultra-wideband response for electromagnetic shielding is presented in this article. In the proposed configuration, a single layer FR4 dielectric substrate is used in which the top metallic layer comprises of combined square and circle loop and the bottom metallic layer comprises of combined swastika shape and circle loop. The proposed FSS exhibits a 13.5 GHz ultra-wide stop band response from 2.3 to 15.8 GHz. The proposed FSS has a fractional bandwidth of 148%, and the structure is polarization insensitive for the incident angles up to 45 0 in both TE and TM modes. The performance of the simulated structure is compared with the fabricated structure and the measured results are in tune with the simulated results. It can be used for shielding applications of Wi-Fi frequency bands 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 6 GHz, X band microwave link communication, and aircraft mobile satellite services.