【作者】 刘强；

【导师】 赵强；

【作者基本信息】 电子科技大学 ， 工程硕士（专业学位）， 2017， 硕士

【摘要】 人工电磁材料是一种人工设计的周期性排列的人造介质,因其具备自然界中材料所不具备的奇异特性而得到研究人员的关注。人工电磁材料的研究工作涉及到多个领域,从电磁学、固体物理、电子学到半导体技术等领域都有电磁材料的身影。非线性人工电磁材料是人工电磁材料的重要组成部分,若要实现人工电磁材料特性的可控性,就必须对人工电磁材料的非线性特性进行系统分析。本论文首先研究了功率对谐振频率的调制这一非线性效应,接着探讨了双谐振模式下增强二次谐波,最后讨论了基于后向波特性增强二次谐波的问题。本论文逐渐深入地探究了人工电磁材料的非线性效应,具体包含以下三部分内容:(1)将常用的电谐振(ELC)结构用作基本的谐振单元,通过调整结构的尺寸使其工作在S波段。结合二极管的模型文件,利用CST仿真软件仿真验证,结果表明功率对本文设计的器件具有调制作用。将表贴变容二极管元件焊接到谐振单元的开口处,使其与ELC结构单元组成一个整体,进行实验验证。实验结果表明,随着入射电磁波功率的增大,本人工电磁材料结构的谐振频率呈现蓝移。(2)设计一种双谐振电磁材料结构,其二次谐波频率和基波频率同时满足谐振条件。仿真结果表明双谐振模式能够有效的提高本人工电磁材料结构产生二次谐波的效率,在入射电磁波功率为0dBm时,双谐振模式下得到的反射二次谐波的能量比单谐振模式下得到的反射二次谐波的能量大3dB。(3)讨论了利用后向波特性控制二次谐波的辐射方向,选取人工电磁材料领域常用到的金属线和开口环两种结构,结合变容二极管的模型文件,在人工电磁材料的左手频域内选择了一个频率点使基波和二次谐波的波矢量刚好满足相位匹配的条件。四层结构与单层结构出现明显的不同。仿真结果表明,功率在-20dBm到20dBm区间内反射的二次谐波功率均大于透射的二次谐波功率,这表明了我们设计的结构的合理性以及证明了利用相位匹配的方法提高实现二次谐波的功率,即反射增强。更多还原

【Abstract】 Metamaterial is an artificial medium for artificial periodic arrangement design.It has been paid more and more attention by researchers because of its unique properties which are not available in nature.Electromagnetic materials research is interdisciplinary,involving electromagnetic,solid physics,electronics,semiconductor technology and other fields.Nonlinear metamaterials are important parts of metamaterials.In order to control the properties of the metamaterials,the nonlinear characteristics of metamaterials must be systematically investigated.In this paper,the nonlinear effect of power modulation on the resonant frequency is studied firs and then discusses the other aspects of the nonlinear effect,second harmonic enhancement in double resonance mode.Finally,the nonlinear effects of metamaterials are further studied,and the second harmonic enhancement based on backward wave is discussed.This paper has gradually explored the nonlinear effects of metamaterials and the main contents include the following three points:(1)The electro-resonant ELC metamaterial structure is used as the basic resonant unit cell,by adjusting the structure size to make it work in the S band.We demonstrate that the power has a modulation effect on the device designed in this paper by using the CST simulation software and Spice file.Then paste the varactor element welded to the opening resonance unit,which forms a whole structure of ELC unit cell.The experimental results show that the resonant frequency of the metamaterial structure shows a blue shift with the increase of the incident electromagnetic wave power.(2)A double resonance electromagnetic material is introduced,and the second harmonic frequency and the fundamental frequency satisfy the resonance condition at the same time.The results show that the double resonant mode can effectively improve the efficiency of the second harmonic generation of the metamaterials structure.When the incident electromagnetic wave power is 0 dBm,the energy of the reflected second harmonic obtained in the double resonant mode is higher 3 dB than that in the single resonant mode.(3)The method of controlling the radiation direction of the second harmonic by using the backward wave characteristic of the second harmonic is discussed.Two kinds of structures commonly used in the field of metamaterials are selected.Combined with the model file of the varactor diode,and a frequency point is selected in the left hand frequency domain of the metamaterials so that it just satisfies the phase match condition.The four-layer structure is obviously different from the single-layer structure.The second harmonic power reflected in the range of-20 dBm to 20 dBm is larger than that of the transmitted second harmonic.The results show that the structure of our design is reasonable and the method of phase matching can be used to increase the power of the second harmonic,namely reflection enhancement.更多还原