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类型 基础研究 预答辩日期 2018-04-04
开始(开题)日期 2015-12-28 论文结束日期 2018-01-22
地点 李文正楼北614 论文选题来源 973、863项目     论文字数 5 (万字)
题目 新型人工电磁表面在隐身中的研究与应用
主题词 新型人工电磁表面,吸波器,随机表面,可调,优化算法
摘要 新型人工电磁表面是一种二维概念上的新型人工电磁材料,它是一种平面阵列,由亚波长尺寸的单元结构组成。由于新型人工电磁表面能够提供强大的电磁波调控能力,因而在过去的十年里引起研究人员的广泛关注,在微波和光学工程领域产生了一系列用途,如异常反射、极化分离、超薄透镜、光学全息等。本论文主要关注新型人工电磁表面在隐身技术领域的研究。主要内容和贡献概括如下: 通过在单元之间加载变容二极管,我们设计、分析、并实验验证了一种极化不明感、频率可调的新型人工电磁表面吸波器。在所设计的频段内,基本单元在不同的角度的入射波激励下,均展现出优异的吸波特性。通过改变变容二极管两端的偏置电压,可以连续的调控基本单元的吸波频率。我们采用电磁波在分层媒质之间多次反透射的干涉理论来探讨吸波机理。为实现吸波器的极化不明感特性,我们将基本单元沿两个正交方向排列组阵,使得吸波器能够吸收任意极化的入射波能量。实验结果显示,所设计的吸波器频率连续可调,调节带宽达到1.5 GHz(相对带宽30%)。 我们提出一种可用于精确设计随机表面带宽的方法。与之前工作不同之处在于,本设计是在一个宽频带内进行的,而不是在点频,这有利于精确设计样品的工作频带。我们采用三种基本单元来组建所设计的随机表面,其漫反射特性可归因于单元彼此之间的相消干涉作用。在设计中,单元本身的损耗也被考虑进去,从而使得理论模型更接近实际的情况。仿真结果和实验结果显示,在预先设定的频带内,随机表面展现出非常好的低散射特性,与理论预测相一致。 我们提出一种用于快速设计超宽带随机表面的方法。所设计的随机表面由三种结构简单具有不同谐振特性的基本单元组成。为在低后向反射率情形下,获取最宽的带宽特性,本设计采用遗传算法来快速、高效的调节单元的谐振,优化单元的尺寸参数。同时,采用逆傅里叶变换方法,在较高精度和极小的计算时间下求解出随机表面的远场方向图,显著提高的阵列设计的效率。我们所提出的快速设计流程在微波、太赫兹频段有着广泛的应用前景,如生物探测和成像等。 为了融合吸波器与随机表面,实现同时采用吸波机理和干涉机理来抑制反射能量,我们设计一种新型隐身表面,它由两种基本单元随机排布构成。通过选用具有合适方阻值的ITO 薄膜进行单元设计,可以在宽频带内提高单元对入射波电磁能量的吸收率。同时,剩余电磁能量会在不同单元之间的产生干涉现象,形成漫反射,从而进一步缩减后向反射能量。实验结果显示,从6.8 GHz 到19.4 GHz 频带内,该新型隐身表面具有很好的隐身特性,与仿真结果相符合。另外,我们所采用的材料均具有光学透明特性,这将让我们的设计在光伏太阳能电池和电磁屏蔽玻璃等方向具有潜在的应用前景。
英文题目 Researches and Applications of Metasurface in Stealth Technology
英文主题词 metasurface, absorber, random metasurface, tunable, optimized algorithm
英文摘要 Metasurface is a 2D equivalence of metamaterial, which is constituted by thin planar array of elements with sub-wavelength scale. It has attracted a great deal of attention during the past decade for its ability to provide full control of the wave-fronts, enabling many applications in microwave and optical engineering, such as anomalous reflection, polarization splitting, ultrathin lens, and optical holography. In this thesis, a detailed research is made on the stealth technology based on metasurfaces. The main contents and contributions of this thesis are summarized below: A polariztion-insentive tunable metasurface absorber is designed with the varactor diodes embedded between the metamsurface units. The basic unit shows excellent absorptivity in the designed frequency band over a wide range of incident angles. By regulating the reverse bias voltage on the varactor diode, the absorption frequency of the designed unit can be controlled continuously. The mechanism of the absorption is interpreted using the electromagnetic-wave interference theory. When the basic units are placed along two orthogonal directions, the absorber is insensitive to the polarization of incident waves. The tunability of the absorber has been verified by experimental results with the measured bandwidth of 1.5 GHz (or relative bandwidth of 30%). A new strategy is proposed to realize the random metasurface with desired diffusion bandwidth. Different from the earlier work, the current design is carried out within a broad spectrum instead of at a single frequency, giving rise to the arbitrarily desired bandwidth. Three basic elements are proposed to construct the new random metasurface, and the diffuse reflection feature can be attributed to their destructive interferences with the change of operating frequency. The intrinsic loss of the meta-atoms is also taken into account to make the theoretical model more accurate in the practical design. Excellent scattering-suppression features are observed in the predefined frequency bands in both simulated and experimental results, which have very good agreements with the theoretical predictions. A method for fast design of broadband random metasurface is presented and experimentally characterized. The proposed random metasurface is composed by three kinds of simply patterned elements with different resonant properties. To obtain the best broadband performance with the lowest backward reflections, a genetic algorithm is developed to manipulate the resonances for the fast determination of element geometries. An inverse discrete Fourier transform method is used to predict the scattering pattern of the metasurface with high accuracy and low time consumption, significantly enhancing the efficiency of the array pattern design. The proposed fast design flow will benefit a broad range of microwave and terahertz applications, such as biological detection and imaging. To realize reflection suppression with the simultaneous control of wave absorption and interference, we propose a new metasurface constituted by two kinds of unit cells in a pseudorandom arrangement. By use of the indium tin oxide (ITO) with moderate sheet resistance in the meta-atoms, enhanced absorption of energy can be achieved in a broad spectrum when interacted with illuminated waves. In the meanwhile, electromagnetic diffusion will be invoked from the destructive interference among the meta-atoms, leading to significant reduction of specular reflection as a result. Excellent agreement are observed between simulation and experiment with pronounced reflection suppression from 6.8 GHz to 19.4 GHz. In addition, the optical transparency of the patterns and substrates makes the proposed metasurface a promising candidate of future applications like photovoltaic solar cells and electromagnetic shielding glasses.
学术讨论
主办单位时间地点报告人报告主题
东南大学 2014.3 李文正楼北614 赵捷 Reflectarray Antenna
东南大学 2014.10 李文正楼北614 赵捷 Transmit Array
东南大学 2014.12 李文正楼北614 Porf. Mingyu Lu Wireless Power Transmission: History, Technologies, and Future
东南大学 2015.03 李文正楼北614 Dr. Bo Zhao 场-路-粒子及多尺寸联合仿真技术
东南大学 2015.04 李文正楼北614 Prof. Levent Sevgi Electromagnetic Diffraction Modeling and Simulation
东南大学 2015.5 李文正楼北614 赵捷 Reconfigurable Reflectarray
东南大学 2016.10 李文正楼北614 赵捷 Controlling the amplitude and phase of metasurfaces
东南大学 2017.12 李文正楼北614 Prof. Yun`s\乿l VE`s\乿l Vfont> High Intensity Focused Ultrasound (HIFU) based thrombolysis using multiple frequency excitations
     
学术会议
会议名称时间地点本人报告本人报告题目
中国电子学会第二十三届青年学术年会 2017.11 成都电子科技大学 随机表面的快速设计方法
Metamaterials2016 2016.9 Chania, Crete, Greece Reduction of RCS Based on a Thin Metasurface
     
代表作
论文名称
A tunable metamaterial absorber using varactor diodes
Controlling the Bandwidth of Terahertz Low‐Scattering Metasurfaces
Fast design of broadband terahertz diffusion metasurfaces
A method for the bandwidth-control of terahertz low-scattering metasurfaces
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
冯一军 正高 教授 博导 南京大学
金飚兵 正高 教授 博导 南京大学
崔铁军 正高 教授 博导 东南大学
蒋卫祥 正高 研究员 博导 东南大学
马慧锋 正高 研究员 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
汤文轩 副高 副教授 东南大学