The dynamic control of electromagnetic waves is a persistent pursuit in modern industrial development. The state-of-the-art dynamic devices suffer from limitations such as narrow bandwidth, limited modulation range, and expensive features. To address these issues, we fuse origami techniques with metamaterial design to achieve ultra-wideband and large-depth reflection modulation. Through a folding process, our proposed metamaterial achieves over 10-dB modulation depth over 4.96 - 38.8 GHz, with a fractional bandwidth of 155% and tolerance to incident angles and polarizations. Its ultra-wideband and large-depth reflection modulation performance is verified through experiments and analyzed through multipole decomposition theory. To enhance its practical applicability, transparent conductive films are introduced to the metamaterial, achieving high optical transparency (>87%) from visible to near-infrared light while maintaining cost-effectiveness. Benefiting from lightweight, foldability, and low-cost properties, our design shows promise for extensive satellite communication and optical window mobile communication management.
There is a huge challenge to target multispectral compatible designs to satisfy the conflicting parametric requirements according to specific engineering requirements. In this work, a novel design method of multispectral compatible integration based on a lossy capacitive multispectral meta-film (MMF) is proposed. The simple guidelines from the impedance matching conditions of MMF derived from the transmission line model were employed to guide and analyze the broadband microwave absorption behavior. An autonomous optimization platform was constructed to simultaneously realize the customization of low infrared emissivity, as well as the widest microwave absorption bandwidth while ensuring maximum visible transparency. Following the guidance of the design method, a flexible structure with a low infrared emissivity of 0.534, wideband microwave absorption from 8.9 to 16.4 GHz covering X, Ku, and high visible transmission of 70.18% and ultra-thin thickness of 2.3 mm was finally obtained. The experimental results and simulation results were in high agreement, indicating the MMF has great application potential in multispectral stealth on optical windows, further demonstrating the versatility and effectiveness of the design method.
Designing an ultra-wideband metasurface absorber is challenging because of its lossy characteristic that hinders the understanding of its resonance behavior. In this study, a framework was formulated to extend the application of the theory of characteristic modes to the analysis and design of metabsorbers. The metabsorber and its lossless counterpart exhibited similar modal behaviors, hence revealing the absorption mechanism of metabsorber. By introducing absorption modes, a dual-band metabsorber was converted into an ultra-wideband metabsorber. This proposed metabsorber with a thickness of 1.99 times the Rozanov's limit could measure a bandwidth of 5.51-36.56 GHz (or 6 octaves) with 90% absorptance.
A conformal metamaterial absorber with simultaneous optical transparency and broadband absorption is proposed in this paper. The absorptance above 90% over a wide frequency range of 5.3-15 GHz can be achieved through topology optimization combined with a genetic algorithm (GA). The broadband absorption can be kept at incident angles within 45° and 70° for TE mode and TM mode, respectively. In the meantime, by employing transparent substrates, including polyvinyl chloride (PVC) and polyethylene terephthalate (PET), good optical transmittance and flexibility can be obtained simultaneously. The experimental results agree well with the numerical simulations, which further validates the reliability of our design and theoretical analysis. With its visible-wavelength transparency, flexibility, broadband absorption, low profile, excellent angle stability and polarization insensitivity, the proposed absorber is highly favored for practical applications in microwave engineering, such as electromagnetic interference and stealth technology. Moreover, the proposed design method of topology optimization can be extended to design the absorber quickly and efficiently, according to specific engineering requirements.
A transparent low-profile polarization-insensitive metamaterial absorber with ultrawideband microwave absorption is presented. A fractional bandwidth of 125.2% (4.3-18.7â GHz, absorptance > 90%) is achieved using a simple patterned resistive metasurface. The thickness of the absorber is only â¼0.086 times the upper-cutoff wavelength. The experimental results agree with full-wave simulation results. A Cu-metal-mesh ground plane enhances the shielding efficiency and visible transparency. Radar cross-sections (RCS) are reduced across all reflection angles, over frequencies spanning the C, X, and Ku bands. With its visible-wavelength transparency, low profile, polarization insensitivity, excellent absorption, and wideband RCS reduction, the proposed absorber has wide applicability.
