高功率微波轴对称模式天线辐射技术研究

【作者】 袁成卫；

【导师】 凌根深；

【作者基本信息】 中国人民解放军国防科学技术大学 ， 光学工程， 2002， 硕士

【摘要】 许多高功率微波源产生的微波模式都是圆波导轴对称模，因此研究轴对称模式的天线辐射技术具有重要意义。本文从理论推导、数值计算和实验等方面研究了两类可以直接辐射轴对称模式的天线—Vlasov天线和COBRA天线。 在理论上，对Vlasov天线和反射面式COBRA天线进行了一系列研究。在Vlasov天线方面：用矢量绕射理论建立了天线辐射场的计算模型并编写了计算程序，该程序计算结果在主瓣上与实验测量吻合良好，近旁瓣也基本一致；利用矩量法计算了天线的反射系数，表明该天线有较小的反射，总的能量反射小于0.25％；详细分析了天线的辐射特性，给出了天线辐射波束相关参数的估算公式和天线设计公式；进一步研究和论证了Vlasov天线辐射高阶轴对称模的可行性；对天线的密封方式和功率容量进行了讨论，结果表明在不需很大密封罩的情况下可以获得GW级的功率容量；为了用Vlasov天线辐射同轴TEM模，研究了TEM-TM₀₁模式转换器的设计，得到了一些基本规律；最后，介绍和分析了带有锥形喇叭的Vlasov天线。在COBRA天线方面：重新阐述了反射面的设计公式，该反射面是几块不同焦距抛物反射面的共焦共轴组合；用电流分布法推导了天线的辐射公式并编写了计算程序，利用该程序对天线的辐射方向图和频带宽度进行了讨论，计算表明这种天线可以在轴线上获得高增益的圆极化波（当反射面直径为1.3m时增益为30dBi），其3dB带宽为78％；推导了同轴TEM模作为COBRA天线馈源时的辐射公式；最后，提出并设计了一种折叠式COBRA天线。 实验上，设计了带有反射面的Vlasov天线并进行了冷测。测量结果表明，所加工天线可以在很宽的频带内（至少3.6GHz-5.6GHz）工作，获得从19dBi到23dBi的较高增益。测量结果和计算结果吻合良好，进一步验证了上述理论计算的正确性。更多还原

【Abstract】 It is important to study the antenna that can directly radiate cylindrically symmetric modes, which are generated by many high power microwave sources. Two kinds of antenna, Vlasov antenna and COBRA, which are suitable for radiating cylindrically symmetric modes, are investigated through theoretic analyses, numerical calculations and experiments.Theoretically, a series of aspects about the Vlasov antenna and COBRA are studied in detail. Firstly, we research the Vlasov antenna with reflector mainly. A new method to calculate the radiation of the antenna is founded with Vectorial Theory of Diffraction, and the corresponding program is made. The reflective characters of Vlasov antenna are studied with Moment Methods, and the results show that the total reflected energy is less than 0.25%. The radiation patterns of the antenna are analyzed, and the formulas to estimate the wave beam parameters and to design the antenna are provided. The feasibility of radiating high-order modes by Vlasov antenna is also discussed and verified. The hermetization of the Vlasov antenna is researched and the results show that with such kinds of hermetization the antenna can work under gigawatt level. The design of the mode converter from TEM to TMoi is studied, which is useful when the TEM coaxial mode is radiated by Vlasov antenna. At last, the flared-end Vlasov antenna is also discussed. Secondly, we examine the COBRA with segmented parabolic reflectors. The design of the reflector is re-expatiated, which is composed of several equivalent parts of parabolic reflector with the same axis and focus. The radiation formulas are deduced with Current Distribution Methods, and the radiation patterns are calculated. The results show that it can produce high-gain circularly polarized field in the boresight direction (the gain is about 30dBi when the diameter of the reflector is 1.3m) and its 3dB bandwidth is 78%. The radiation formulas of TEM coaxial mode as the radiation mode of COBRA are also deduced. At last, a new folding antenna has been put forward and designed.Experimentally, a Vlasov antenna has been designed and tested at low power. The measured results show that that antenna can work in wide bandwidth (at least from 3.6GHz to 5.6GHz) with gain varying from 19dBi to 23dBi. The measured results agree well withnumerical results, which proves again the validity of our numerical methods.更多还原