A Broadband Rasorber with High-Efficiency In-Band Transmission Window Utilizing the Slotted Circular Resonator

Abstract

In the past decade, rasorber has aroused extensive attention due to its promising applications in stealth of wireless facilities. Here, we proposed and demonstrated a broadband rasorber with high-efficiency in-band transmission window. The equivalent circuit model (ECM) of a typical rasorber was established and the general criterion for the impedance of the lossy metasurface was derived. According to this criterion, we deployed a lumped resistor loaded square ring with four slotted circular resonators as the frequency selective absorbing meta-atom. Loss caused by the loaded resistors will be shunned at the identical resonant frequency of the slotted circular resonator and band-pass frequency selective surface (FSS), so that the rasorber can obtain a high-efficiency in-band transmission window. Simulation results indicate the proposed rasorber can achieve absorption rates higher than 80% at both a lower band (2.29 ~ 6.02 GHz) and a higher band (7.02 ~ 9.97 GHz). Meanwhile, there is an in-band transmission window with minimum insertion loss as 0.17 dB around 6.5 GHz. In addition, the rasorber is equipped with certain robustness against oblique incidence. As the verification, a prototype was fabricated and the measured results coincide well with simulated results.

Keywords: rasorber, Metasurface, broadband absorbing, in-band transmission, slotted circular resonators