【作者】 梁志伟；

【导师】 朱光武； 徐跃民；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 空间物理学， 2008， 博士

【摘要】 随着通讯技术的不断发展与等离子体技术的日益成熟,将等离子体天线替代传统金属天线应用于通讯系统已经成为相关领域研究的一大热点。因此本文重点研究了不同等离子体参数条件下HF/VHF频段柱形单极等离子体天线的动态重构特性,包括柱形等离子体天线的基本理论、计算机仿真和技术实现,柱形等离子体天线电参数的数值求解,等离子体天线输入阻抗、噪声、增益等电参数的测量及分析。通过这些研究旨在探明可重构柱形等离子体天线的实现方法,为等离子体天线技术趋于实用化提供必要的理论及技术准备。目前已经初步实现了柱形等离子体天线系统的结构设计,完成了柱形等离子体天线理论模型的矩量法分析,建立了柱形等离子体天线特有的电参数测量系统。作者的主要工作和结果可以概括为:1.基于表面波激励等离子体的基本原理以及表面波在等离子体中的传播特性,给出了柱形等离子体天线耦合腔体的结构设计。应用仿真软件研究了激励频率和信号频率在耦合腔体中的电磁特性,并根据仿真结果实现了柱形等离子体天线系统的结构设计,包括等离子体参数、天线尺寸、天线耦合模式、HF/VHF频段滤波器等。2.基于矩量法计算了当等离子体天线工作频率远小于等离子体频率时,密度均匀分布的柱形等离子体天线表面电流分布、辐射方向图、输入阻抗、天线效率以及增益等天线参数。计算结果表明等离子体天线具有与金属铜天线类似的辐射特性,并且随等离子体参数变化而改变。此外既可以通过等离子体天线的动态重构,也可以在损失部分效率的前提下选取固定的等离子体参数,获得天线的宽带特性。3.采用驻波比推算法测量了不同激励功率条件下等离子体激励通道电离阻抗,设计完成的激励通道匹配电路满足不同激励功率条件下驻波比小于2。4.提出了一种新的通过矢量网络分析仪测量大功率条件下等离子体天线信号通道输入阻抗的测试方法,该方法有助于等离子体天线动态重构特性的研究和实现快速阻抗匹配。实验中测量了不同激励功率条件下柱形等离子体天线系统的输入阻抗随频率的变化关系,结合放电管的等效电路模型与柱形等离子体天线输入电流特性,定性分析了等离子体天线输入阻抗变化与等离子体参数之间的关系。实验结果表明柱形等离子体天线输入阻抗曲线具有明显的谐振特性。通过软件仿真和实际电路调试完成了天线信号通道HF频段的匹配设计,初步验证了天线的宽带特性。5.分析了利用等离子体天线代替金属天线时,系统通讯过程中噪声的来源、大小及其对系统的影响,并采用不同的测量原理通过无线电综合测量仪和频谱仪两种仪器得到结果近似的等离子体天线系统馈端的系统等效噪声温度。实验结果表明等离子体天线可以代替金属天线用于射频通讯。更多还原

【Abstract】 With the development of communication and plasma technology, the research of using the plasma antenna to replace the traditional metal antenna in the communication system becomes one of the hotspot in related fields. Thus the dynamic reconfiguration of the plasma-column antenna in the HF/VHF range is focused for different plasma parameters. This thesis covered the contents about the basic theory and CAD of plasma-column antenna, numerical calculation of plasma-column antenna electrical parameters, and also measurement and analysis of plasma-column antenna input impedance, noise temperature and gain. The aim of these works is to confirm the possibility of realizing plasma-column antenna dynamic reconfiguration, so that the theoretical principle and technological preparations for the application of plasma-column antenna should be made.Presently, the author has realized the mechanical design of original plasma-column antenna system, accomplished the numerical simulation of the radiation characteristics of plasma antenna based on two-dimensional moment method, created the special measuring system for plasma-column antenna electrical parameters. The author’s major contributions are as follows:1. The coupling structure of plasma column antenna was presented based on the elementary theory of surface wave plasma excitation and the propagation characteristics of surface wave in plasma. Then the design of plasma-column antenna system is realized according to the simulation results of the electromagnetic property of excitation and signal frequency inside the structure, including the plasma parameters, the dimension of plasma-column antenna, the coupling modes and the HF/VHF filters .2. The numerical analyses of the radiation characteristics of a plasma-column antenna is presented by using the moment method when the operating frequency is greatly lower than the plasma frequency, including current distribution along the plasma column, radiation pattern, input impedance, antenna efficiency and gain. It has been demonstrated that the plasma antenna can operate similar to a copper antenna, and the radiation characteristics can be varied by varying the plasma parameters.Furthermore,not only the dynamic reconfiguration of the plasma antenna, but also selecting fixed plasma parameters with reduced efficiency enables the wideband characteristics of plasma antenna.3. The ionization impedance of the exciting channel of plasma-column antenna was calculated based on the VSWR calculation for different applied RF power. Then an impedance matching electro circuit of this channel was designed, which made the VSWR always less than 2 for different applied power.4. The input impedance of the signal channel of plasma-column antenna in high exciting power was measured by a new method, which is useful to the study of plasma antenna dynamic reconfiguration and the realization of fast impedance matching. The changes of the input impedance of the signal channel of plasma-column antenna with frequency have been measured by the vector network analyzer for different applied RF power. The relationship between the impedance curves and the plasma parameters was proposed by using the equivalent circuit model and the characteristics of input current. The experimental result shows the resonance behavior of the impedance curves is prominent. A broadband matching electro circuit was designed by the software, and then a hardware matching electro circuit was realized in the HF range, which validated the broadband characteristics of plasma-column antenna.5. The noise source and magnitude which affects the performance of the communication system was discussed when the plasma antenna replaced the traditional metal antenna. Then the noise temperature of the plasma antenna feed was measured in two methods by using RF communications test set and Spectrum Analyzers. The result shows the plasma antenna can be used in radio communication instead of metal antenna.更多还原