Design of an ultra‐broadband microwave metamaterial absorber based on multilayer structures

Abstract

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.

Design and analysis of actively tunable absorbers combined with diodes and magnetic material

“…To further understand the physical mechanism of the absorption of the diode, an equivalent circuit model is proposed according to transmission line theory as shown in figure 13 [15]. The length of transmission lines h 1 and h 2 are equivalent to the thickness of the magnetic medium layer and the FR-4 layer.…”

Ultra-thin wideband frequency tunable metamaterial absorber and its application for antenna radar cross section reduction

“…Therefore, the key to designing high-performance MMAs lies in achieving a balanced relationship among these three factors. Numerous passive MMAs have successfully expanded their absorption bandwidth through the implementation of multi-layer cascade structures [15][16][17], fractal designs [18][19][20] and incorporation of lumped elements [21][22][23]. Nevertheless, these enhancements also require the implementation of structures with larger profile heights, and once the fabrication is completed, their operational performance becomes fixed.…”

Ultrawide Spectra Camouflage Coatings from Metallic Flake Powder

“…However, the rapid development of detection technology makes the single-band stealth no longer able to handle the broad-spectral synergy and complexity of detection systems. , Instead, functional materials with ultrawide spectra camouflage are required. Since the camouflage mechanisms and operation modes for diverse electromagnetic bands are different or even mutually exclusive, there remains a longstanding challenge to achieve compatible stealth. , To satisfy the requirements of broad-spectral-compatible camouflage, the spectral properties of the material should have (i) low emissivity in the mid-IR (MIR) and far-IR (FIR) atmospheric windows (3–5 and 8–14 μm, respectively) to conceal its characteristics of infrared radiation, − (ii) low reflectance in the VIS band (400–800 nm) with diffuse reflection to reduce visible energy access to the detector, , and (iii) high absorption in the MW radar band (S–Ku bands, 2–18 GHz) and wide effective absorption bandwidth (EAB) to reduce the radar cross section (RCS). , The main mechanism for the microwave absorption (MA) is to convert electromagnetic energy into heat energy by dielectric loss and magnetic loss . When the extra heat induced by microwave absorption is added to the targets, the temperature of targets will mismatch with that of environment and expose their infrared radiation signature.…”

“…12,13 The main mechanism for the microwave absorption (MA) is to convert electromagnetic energy into heat energy by dielectric loss and magnetic loss. 14 When the extra heat induced by microwave absorption is added to the targets, the temperature of targets will mismatch with that of environment and expose their infrared radiation signature. According to the Stefan−Boltzmann law, controlling the temperature and surface emissivity are two methods to achieve IR camouflage.…”