Ultra-miniaturized frequency-selective rasorber with P/L-band absorption and C/X/Ku-band transmission for low-frequency RCS or EMI suppression of ultra-wideband antennas

Abstract

In this paper, a miniaturized frequency-selective rasorber (FSR) with an ultra-wide absorption band in the P, L-band and an ultrawide transmission window in the C, X, and Ku-band simultaneously is theoretically proposed and experimentally verified. Unlike introducing a transmission window based on paralleled LC resonance, the non-resonant transmission nature of the lossy layer is investigated and applied to achieve ultra-wideband transmission of the proposed FSR. Secondly, meander lines and lumped components are utilized in the lossy layer to suppress the undesired harmonic resonance in the transmission band and achieve miniaturization. The proposed FSR is finally realized by combining the lossy layer with a multilayer sandwich-liked wideband bandpass frequency-selective surface (FSS). Measured results are in considerable consistency with the simulation ones and illustrate that the prototype of the proposed FSR achieves over 90% absorption from 500 MHz to 2.25 GHz with a fractional bandwidth of 127.3% and a -1-dB transmission bandwidth of 100.0% covering 4.6–13.8 GHz. The unit cell’s size is only 0.026 ${\lambda }_L\times 0.026{\lambda }_L\times 0.10{\lambda }_L$ (${\lambda }_L$ is the free-space wavelength at the lowest operation frequency). The proposed FSR is of great potential in low-frequency radar stealth or electromagnetic interference (EMI) shielding applications for emerging wideband and ultra-wideband antenna systems.