Flexible and transparent ultra-broadband low-profile frequency selective rasorber

An ultra-broadband, low-profile, flexible, and transparent frequency selective rasorber (FSR) is designed based on indium tin oxide (ITO) film. The -1 dB transmission band of the resistive sheet and the bandpass FSS are 0.10 - 8.61 GHz and 3.09 - 7.09 GHz, respectively. By integrating the resistive sheet and the bandpass FSS, a transmission band ranging 1.95 - 6.27 GHz with |S₂₁| larger than -3 dB is achieved, alongside an absorption band ranging 7.34 - 10.83 GHz with absorptance larger than 0.8. Additionally, the FSR presented in this paper is designed by single-layer bandpass FSS and adopts coplanar coupling to realize an ultrabroad transmission band. Its ultra-broadband absorption and transmission performance are verified through experiments and the working principles are analyzed through an equivalent circuit model (ECM). The proposed FSR possesses unique advantages integrating ultrabroad band, optical transparency, flexibility, low profile, and light weight. The proposed FSR exhibits the potential to reduce the out-of-band radar cross-section (RCS), with its optical transparency showing promise for window applications.