Dual-polarized third-order wideband bandpass frequency selective surface for X band and Ku band application

A third-order dual-polarized elliptic wide passband Frequency Selective Surface (FSS) has been proposed in this article. The unit cell is comprised of Y-shaped fractal geometry integration on the tri-pole and evolved as the stub-loaded tri-pole (SLTP) structure on an ultra-thin FR-4 substrate (ϵr = 4.4). The novel back-to-back cascading approach of the aforesaid proposed design array with optimized air spacer enhances electromagnetic coupling, resulting in maximally flat and substantially wider third-order bandpass filtering capability. −3 dB passband filtering performance (8.3–20.1 GHz) and −1 dB transmission characteristics (8.9–19.8 GHz) encompass the X and Ku band spectral ranges. The elliptical transmission coefficient leads to a remarkable passband selectivity factor (SF = 0.91). Equivalent circuit models (ECM) have been mapped, and the prototype has been experimentally validated. Angular stability (θ ≤ 40°) for both TE and TM polarizations ensures the employability of the proposed FSS for the radome.