In this paper, we present a novel, to the best of our knowledge, 3D ultra-broadband tunable metamaterial absorber (TMA), which is innovatively tuned by the gravity field with changing the position of the liquid metal (eutectic gallium-indium) in theory. The given TMA consists of a 3D glass cavity filled with the liquid metal, two-layer high-impedance surfaces, two dielectric layers, and a metallic plate on the bottom. The ultra-broadband absorption is achieved by the high-impedance surface and the liquid metal. Furthermore, it is noted that the liquid metal is poured into the different parts of the glass cavities via rotation under the action of the gravity field to obtain the tunable absorption. When such a TMA is not rotated, for the TE wave, the absorption rate exceeds 90% from 1.8 to 57.5 GHz with a wide relative absorption bandwidth (AB) of 187.8%. However, for the TM wave, the absorptivity goes beyond 90% at 5.6–56.4 GHz. The proposed TMA exhibits ultra-broadband absorption in the frequency regime of 1.6–45.3 GHz (the absorption rate is higher than 90%) with such a TMA rotated 180° in the $x {-} y$ plane, while the absorption rate is near zero from 1.6 to 60 GHz when the proposed TMA is rotated 180° in the $y {-} z$ plane. Moreover, the surface current distributions, the near-field amplitude $|{E_z}|$, the phase ${\varphi _z}$, and the magnetic field distributions are investigated to describe the operating mechanism of the designed TMA. Besides, the numerical results indicate that such a TMA can realize high absorption under a wider incident angle. Compared with traditional tunable devices, the gravity field regulation, which can change the operating frequencies of an absorber in a noncontact way, has the advantages of easy implementation and resource savings. The proposed absorber tuned by the gravity will have potential applications in frequency selection. With the change of liquid metal and structure design, this design can also be potentially applied in other microwave and terahertz devices. Taken together, this study suggests a role for such an absorber in promoting a novel application for tunable devices.

中文翻译：

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基于高阻抗表面的三维重力定制超宽带吸收器

在本文中，根据我们所知，我们提出了一种新颖的3D超宽带可调谐超材料吸收器（TMA），它通过重力场随着液态金属（共晶镓-铟）的位置变化而进行了创新性的调谐。理论。给定的TMA由填充有液态金属的3D玻璃腔，两层高阻抗表面，两层介电层以及底部的金属板组成。通过高阻抗表面和液态金属实现超宽带吸收。此外，应注意，在重力场的作用下，通过旋转将液态金属倒入玻璃腔的不同部分中以获得可调吸收。当这样的TMA不旋转时，对于TE波，吸收率从1.8到57超过90％。5 GHz，相对吸收带宽（AB）为187.8％。但是，对于TM波，在5.6-56.4 GHz时吸收率超过90％。拟议的TMA在1.6–45.3 GHz的频率范围内表现出超宽带吸收（吸收率高于90％），而TMA在输入端旋转180°。$ x {-} y $平面，而当建议的TMA在$ y {-} z $平面中旋转180°时，吸收率从1.6到60 GHz接近零。此外，表面电流分布，近场幅度$ | {E_z} | $，相位$ {\ varphi _z} $，并研究了磁场分布，以描述所设计的TMA的工作机理。此外，数值结果表明，这样的TMA可以在更宽的入射角下实现高吸收。与传统的可调设备相比，重力场调节可以以非接触方式改变吸收器的工作频率，具有易于实施和节省资源的优点。通过重力调整的拟议吸收器将在频率选择方面具有潜在的应用。随着液态金属和结构设计的变化，该设计也可能会应用于其他微波和太赫兹设备。两者合计，这项研究表明这种吸收器在促进可调谐设备的新型应用方面的作用。