An ultra-broadband double-layer microwave metamaterial absorber (MMA) with reflectivity below À10 dB ranging from 1.4 to17.31GHz is presented in this article. The MMA has a fractional bandwidth of 170% and a total thickness of 20.8 mm. By analyzing the function of different layers, the MMA can be simplified to the combination of a dual-band (DB) absorber and a single-band (SB) absorber. Layer I consists of a square loop loaded with asymmetric resistors and achieves a DB absorption by exciting high-order modes covering the low-frequency and high-frequency. Layer II is composed of double-ring structures integrated with resistors and realizes an SB absorber in the middle frequency. To understand the physical mechanism in detail, the equivalent circuit model (ECM) is proposed and illustrates a good impedance match within the entire absorption bandwidth with free space. An in-depth analysis has been carried out by illustrating several key dimensions. To verify our idea, a prototype has been designed, fabricated, and measured. Measurement results show an ultra-broadband absorption with the reflectivity below À10 dB ranging from 1.7 to 17.27 GHz under the normal direction, which agrees well with simulation and ECM results.
In this paper, the soft and hard composite patterns for electromagnetic scattering control at both normal and grazing incident angle is proposed. The soft and hard parts are composed of dielectric substrate sandwiched by transverse or longitude metal strips with metal via and the perfect electrical conductor ground, and these two parts are combined at a certain inclination angled to form the soft and hard composite patterns. The simulation results demonstrate that the proposed composite patterns have the monostatic radar cross‐section (RCS) reduction of 20.79 and 18.36 dB at 11.24 GHz under normal incidence for transverse electric polarization and transverse magnetic polarization, respectively. Also, this structure achieves 2.78 and 5.43 dB monostatic RCS reduction under grazing incidence from 60° to 90°. The simulation results are in good agreement with the experimental ones. The physical mechanisms of the proposed composite patterns can be elucidated by the equivalent impedance method based on its near‐field distribution. The proposed composite patterns can be functionalized by changing the electromagnetic parameters of the soft and hard surfaces, which has a great potential to be used as the traveling wave antenna enclosure for scattering control.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.