等离子体参数对偶极子天线辐射特性影响研究

发布时间：2018-06-20 16:23

本文选题：等离子体 + 偶极子天线　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：偶极子天线作为电小天线的一种特殊形式,具有较低的辐射电阻和较高的电抗,辐射效率较低,采用超材料加载可使得电小天线的辐射效率大大提高。作为一种特殊的“超材料”,当等离子体频率与电磁波频率满足一定关系时,等离子体可被视为一种有效介电常数为负的超材料。相对于通过结构设计得到的负介电常数介质,等离子体参数较易控制,便于通过控制外施参量来调制偶极子天线的辐射特性。本文以提高偶极子天线的辐射效率为目标,建立等离子体层包围偶极子天线模型,从数值仿真、等效电路模型和实验验证三方面入手,计算并分析相对辐射功率随等离子体参数的变化规律,主要研究内容包括:从偶极子天线的辐射特性出发,推导天线的近场特性、远场特性及方向特性;基于Drude模型,导出等离子体的本构参数,从而得出等离子体在模型中的表征形式;进而建立等离子体层加载偶极子天线辐射模型,并对模型结构、控制方程、边界条件和数值计算方法进行分析、讨论;为了探究等离子体参数对辐射特性的影响规律,本文计算并分析了相对辐射功率随等离子体形状、碰撞频率及密度分布的变化规律,结果表明:在一定参数范围内,包裹馈源的等离子体层比较薄、等离子体碰撞频率小、等离子体密度随径向减小的分布形式有利于天线辐射能力的增强。在此基础上,从近场特性及远场特性角度进行了增强机制分析;为了更加直观便捷的解析等离子体参数对天线辐射的影响,建立了等离子体层加载偶极子天线等效电路模型,从电容电感谐振角度进行电路分析,研究了等离子体密度、碰撞频率及厚度对天线辐射的影响。但是该电路模型不能反映等离子体形状、密度非均匀分布等特性,需进一步完善;在上述研究基础上,明确了提高偶极子天线辐射效率的等离子体层关键参数范围,通过与等离子体加载天线的实验数据相对比,二者定性符合情况良好,在一定程度上验证了数值仿真模型的正确性。但是由于实验情况的复杂性,仿真结果与实验结果在定量方面尚存在一定差异。此外,对二维辐射模型进行了拓展,在前者基础上构建三维模型,并探究了不同密度等离子体层对天线辐射的影响特性。
[Abstract]:As a special form of small electric antenna, the dipole antenna has lower radiation resistance, higher reactance and lower radiation efficiency. The supermaterial loading can greatly improve the radiation efficiency of the small electric antenna. As a special "supermaterial", plasma can be regarded as a kind of metamaterial with negative effective dielectric constant when the frequency of plasma and the frequency of electromagnetic wave satisfy a certain relationship. Compared with the negative dielectric constant obtained by structural design, the plasma parameters can be easily controlled and the radiation characteristics of the dipole antenna can be modulated by controlling the external parameters. In order to improve the radiation efficiency of the dipole antenna, a plasma layer surrounded dipole antenna model is established in this paper, which starts with three aspects: numerical simulation, equivalent circuit model and experimental verification. The variation of relative radiation power with plasma parameters is calculated and analyzed. The main research contents are as follows: from the radiation characteristics of dipole antenna, the near-field, far-field and directional characteristics of antenna are derived, and based on Drude model, The constitutive parameters of the plasma are derived, and the characterization of the plasma in the model is obtained, and the radiation model of the plasma layer loaded dipole antenna is established, and the governing equation is obtained for the structure of the model. In order to investigate the influence of plasma parameters on radiation characteristics, the variation of relative radiation power with plasma shape, collision frequency and density distribution is calculated and analyzed. The results show that the plasma layer wrapped in the feed source is thin and the plasma collision frequency is small within a certain range of parameters. The distribution of plasma density decreases with the radius of the antenna which is beneficial to the enhancement of the radiation ability of the antenna. In order to analyze the effect of plasma parameters on antenna radiation more intuitively and conveniently, the equivalent circuit model of plasma layer loaded dipole antenna is established. The effects of plasma density, collision frequency and thickness on antenna radiation are studied by circuit analysis from the point of view of capacitive inductance resonance. However, the circuit model can not reflect the characteristics of plasma shape and density non-uniform distribution, and needs to be further improved. On the basis of the above research, the range of key parameters of plasma layer to improve the radiation efficiency of dipole antenna is defined. Compared with the experimental data of plasma-loaded antenna, the qualitative agreement between them is good, and the correctness of the numerical simulation model is verified to a certain extent. However, due to the complexity of the experiment, there are still some differences between the simulation results and the experimental results in quantitative aspects. In addition, the two-dimensional radiation model is extended to construct a three-dimensional model based on the former, and the effects of plasma layers of different densities on antenna radiation are investigated.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN821.4

【相似文献】