【作者】 李彪；

【导师】 尹应增；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2014， 博士

【摘要】 由于超材料具有一些天然材料所不具备的超常物理特性，近年来引起了国内外学者的广泛关注。在THz频段，利用超材料与电磁波的强烈电磁响应，可以实现THz频段的功能器件。石墨烯作为近年来新材料研究中另一个备受关注的热点，在THz频段的电磁学领域同样具有广阔的应用前景。本文中紧随当今电磁功能材料领域的研究热点，分析并设计了多款THz频段的电磁功能材料、器件及天线，并对部分模型进行加工和测试；利用电磁功能材料的特殊性质，将其应用于基站天线的设计之中，提高性能并减小天线的尺寸。作者的主要工作及创造性成果可概括为：1. THz频段超材料特性的分析和研究。分析传统开口谐振环在THz频段的材料特性及谐振原理，针对开口谐振环加工难度大和极化敏感的问题，提出同样基于R-L-C谐振的方形闭合环结构并详细分析其特性。利用材料特征的结构相关性，通过采用嵌套的方形环及方形环与十字形环组合的形式，设计多种在THz频段具有双频、三频特性且对入射波极化不敏感的超材料。使用砷化镓工艺线对样品进行加工并利用THz-TDS系统对材料的透射参数进行测试，测试结果与仿真结果吻合良好，验证了超材料设计的正确性。2. THz频段电磁功能器件的设计与分析。在方形金属环的基础上，利用对偶原理，采用镂空方形环结构设计一款THz频段的滤波器并分析了其特性。利用n型砷化镓衬底的半导体特性，设计一款基于方环结构的THz频段的有源调制器并分析其工作原理，通过调节金属电极两端的加载电压改变其透射率实现幅度调制。设计一款基于方环结构的双频THz吸波材料，实现在峰值处超过90%吸收率的吸收特性，并通过等效表面阻抗理论及去耦的Fabry-Perot谐振腔理论分析吸波材料的工作原理，验证设计结果。3.石墨烯材料在电磁学领域中的应用研究。在研究石墨烯表面电导率模型的基础上，对采用石墨烯材料的THz偶极子天线的特性进行了研究。与传统金属材料相比，石墨烯的表面等离子体特性使其产生慢波效应，天线的谐振尺寸可以达到十分之一甚至二十分之一空气中波长，大大减小天线的尺寸，并可以通过调节石墨烯的化学势来改变谐振频率。采用石墨烯材料作为贴片单元设计一款THz频段的平面反射阵天线，其单元间距小于空间波长的六分之一，并且单元的反射相位可以通过化学势来调节，使其具有电调的应用潜力。基于超材料结构设计一款THz石墨烯吸波材料，采用等效电路理论对其工作原理进行分析和验证，并利用光刻工艺对样品进行制作，样品的精度和质量都很好，为接下来的工作奠定了基础。4.电磁带隙结构在天线设计中的应用。针对无线通讯系统的极化分集技术设计两款基于折合振子的双同轴馈电贴片天线，具有低交叉极化与高端口隔离度的特性。在此基础上，将电磁带隙结构作为反射板应用于基站天线单元设计，提出两款低剖面、低交叉极化、高端口隔离度的双极化天线单元。与之前的设计相比，其高度降低了一半且方向图的前后比得到提高。另外，采用高阻抗反射板设计了一款具有低剖面特性的圆极化天线。文中对所设计的天线进行详细的分析，并通过加工测试验证设计的正确性，天线的性能优越，可用于基站及无线热点等通信系统中。电磁功能材料的引入为天线设计开启了一扇新的大门。更多还原

【Abstract】 Metamaterial which has some peculiar physical properties has aroused wideattention all over the world recently. In the THz spectrum, the THz function devices canbe realized by using the strong electromagnetic response between metamaterial andelectromagnetic wave. As one of the new research focus in THz electromagnetism field,graphene also has a broad application prospect. This article followed the currentresearch hotspot in the field of electromagnetic functional materials. The analysis anddesign of many THz electromagnetic functional materials, devices and antenna areproposed and some of these models are processed and tested. The special properties ofelectromagnetic functional materials can be applied to the base station antenna design toimprove the performance. The author’s main contribution can be summarized as:1. Analysis and research of the metamaterial in THz spectrum. The materialproperties and resonant principle of traditional Split Ring Resonator in THz spectrum isanalyzed. The R-L-C resonance square loop structure is designed to overcome thedifficulty in processing and polarization sensitivity. For the correlation with materialcharacteristics and structure, by adopting the nested square loops and cruciform andsquare loop combination form, a variety of THz metamaterials which is insensitive toincident wave polarization with dual-band and tri-band characteristics is implemented.The sample is fabricated by using GaAs processing line and tested by THz-TDS system.The results agree well with the simulation, which verified the design.2. Design and analysis of THz electromagnetic functional device. On the basis ofthe square metal loop and duality theory, a THz band filter composed of hollow squareloop is designed. By using the semiconductor properties of n-type GaAs substrate, aTHz active modulator based on the square loop structure is designed and analyzed. Thetransmissivity can be adjusted by varying the voltage between the metal electrodes. Adual-band THz absorber based on square loop structure is proposed and it can realizemore than90%absorption at the peak point. The characteristics of the absorber areanalyzed and demonstrated by the method of equivalent surface impedance theory anddecoupling Fabry-Perot cavity model.3. Application research of graphene in the field of electromagnetism. Based on theconductivity model of graphene surface, a THz dipole antenna is designed. Comparedwith the traditional metal materials, the surface plasma resonance properties of graphene make it has a slow wave effect. The resonance length can reach one tenth or twentieth ofthe wavelength in the air, which greatly reduced the size of the antenna. And theresonance frequency of graphene can be changed by adjusting the chemical potential. ATHz reflection array antenna is proposed based on the graphene. The element spacing issmaller than one sixth of the wavelength in the air and has great potential in electricallycontrolling application. Based on the metamaterial structure, a THz graphene absorberis designed, which is analyzed by equivalent circuit theory. By using lithographyprocess, the THz absorber based on graphene is fabricated. The precision and quality ofsample are good, which laid the foundation for the next work.4. Application research of EBG structure in antenna design. Firstly, focus on thewireless communication system, two models of double coaxial feed patch antenna withlow cross polarization and high port isolation is design. On this basis, by using the EBGstructure as a reflection plate, two low profile dual polarized antenna with low crosspolarization and high port isolation is proposed. Compared with the previous design, theheight is lowered about a half and the front-back ratio is improved. Then, a circularpolarized antenna with low profile characteristic is design by applying high impedancereflector. The proposed antennas are analysis in detail and fabricated to verify the design.The introduction of electromagnetic functional materials lead a new way for antennadesign.更多还原