In this paper, two kinds of dual-band metamaterial absorbers (MMAs) with stable absorption performance based on fractal structures are proposed. As the key feature, with the increase in fractal order, the fractal MMAs can reduce the weight while keeping the absorption performance. The multi-band absorption property is analyzed by multiple L-C resonances generated by the fractal structure. By virtue of good impedance matching characteristics and the synergy of the circuit and electromagnetic resonance, effective and stable microwave absorption is readily achieved. Finally, two prototypes are fabricated for demonstration, and the measurement result is consistent well with the simulation one. As expected, the proposed fractal MMAs have the advantage of low-cost, light-weight, and dual-effective absorption bands, and have great potential in the application of multi-band radar stealth.
In this paper, an active metasurface microwave absorber with reconfigurable bandwidth and absorption intensity is proposed. The metasurface unit adopts a metallic-backed structure, and its thickness is approximately 0.08 times the free-space wavelength. As the key feature, the structure with reconfigurable bandwidth and absorption intensity is adopting hollow Jerusalem-cross-shaped pattern-loaded PIN diodes. By virtue of the synergy of the dielectric and ohmic loss, effective and stable microwave absorption is readily achieved, and the simulation results obtained from high frequency structure simulator and advanced design system are in agreement. The reconfigurable absorption bandwidth of the metasurface covers C-band, X-band, and Ka-band, with reconfigurable absorption intensity up to 13 dB range. Then, the sample prototype is fabricated for demonstration, and the measurement result is consistent well with the simulation one. In addition, the structure also has a small reflection in a wide reflection angle space (−60°–60°), which is of great significance for radar stealth.
In this paper, a flexible metasurface with dual functions of absorption and polarization conversion is proposed and applied for radar cross section (RCS) reduction. The metasurface unit adopts a metallic-backed structure, and its width and thickness are approximately 0.62 and 0.24 times the free-space wavelength at the center working frequency, respectively. Different from the traditional metasurface, the resonators with low-frequency absorption and high-frequency polarization conversion are horizontally combined to achieve dual-function integration without the use of tunable elements. The structure adopts a flexible substrate, which is also suitable for conformal conditions. From 3.74 to 14.84 GHz, the metasurface has good impedance matching characteristics. The metasurface performs effective absorption and polarization conversion in the frequency bands of 3.78–6.34 GHz and 7.90–14.80 GHz, respectively. The absorption is mainly achieved through the ohmic loss of the lumped resistance, while the polarization conversion is performed through the electromagnetic resonance of the metallic structure. Then, the sample prototype is fabricated for demonstration, and the measurement result is well consistent with the simulation one. Furthermore, the checkerboard-arrangement array of the metasurface and its mirror unit can efficiently reduce the RCS over 7 dB in the range of 3.52–15.28 GHz. As expected, the proposed flexible metasurface can not only be used as an absorber/polarization converter but also be combined to realize broadband RCS reduction, which is of great significance for multi-function and conformal stealth applications.
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