FSS-based Rasorber with Wideband Absorption and Tunable Transmission

Abstract

A polarization-independent T-A type active frequency selective rasorber (AFSR) with a tunable transmission band and wideband absorption is presented in this paper. There are two layers in the proposed AFSR. The bottom layer is a bandpass frequency selective surface (FSS) integrated with a varactor diode-based active filter layer separated by an air spacer, and the top layer is a wideband quasi-single absorptive layer loaded with lumped resistors. A full wave simulation was carried out to analyze the proposed structure. The reflection coefficient of the proposed structure is observed to be less than -10 dB from 4.43 GHz - 9.98 GHz (77%). The absorption bandwidth spans a fractional bandwidth of 75.52% from 4.45 GHz to 9.85 GHz and permits over 90% absorption. This range includes a portion of the X-band and nearly the whole C-band. Furthermore, the transmission band with the lowest possible insertion loss (IL) can be tuned between 2.7 and 4.3 GHz. The proposed geometry offers a stable response up to 40° to the oblique incidence for TE and TM polarized waves, with a thickness of 0.052λ concerning the lowest frequency. The suggested AFSR could have practical uses in stealth and airborne applications. © 2024 IEEE.