Multifunctional Radome-Based Frequency Selective Surface Composites for Stealth Applications

In this letter, we propose multifunctional radome-based frequency selective surface (FSS) composites for stealth applications. The proposed composite simultaneously implements band stop characteristics in the X-band and band pass characteristics in the K- and Ka-bands. The composite consists of a sandwich structure, where two FSS layers are separated by a constant spacing. Thick dielectric materials with higher permittivity and loss tangent than air degrade the filtering performance. We thus performed conformational space annealing (CSA)-based optimization on both the FSS shape and dimension, resulting in a miniaturized pixelated FSS. This approach effectively addresses the downward shift in the resonance frequency by employing an FSS that is 22% smaller than a standalone FSS. We validated the proposed composite through simulations and measurements under varying polarizations and incident angles. The proposed composite achieved insertion losses greater than 20 dB across the entire X-band at a 45° oblique incidence in transverse electric (TE) mode. Under transverse magnetic (TM) mode at a 30° oblique incidence, the composite allowed transmission in the dual K-band and Ka-band while maintaining insertion losses below -18 dB within the stop-band.