【作者】 赵柳；

【导师】 刘庆想；

【作者基本信息】 西南交通大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 传统的天线技术已经具备相当雄厚的理论和工程基础,但是在新兴的高功率微波研究领域,电磁波具有功率高、输出模式为旋转轴对称模等特点,因此对高功率微波天线提出了新的要求。为此,国内外进行了许多研究工作,提出了模式变换器接辐射喇叭、Vlasov天线、模式转换天线以及径向线阵列天线等高功率微波天线型式。上述天线各有特点,经分析比较,我们认为径向线阵列天线应用于高功率微波领域有其独特的优势,可以实现天线的高功率容量、高效率、小型化和圆极化辐射,但由于耦合探针的调节范围有限而无法实现高增益。为此,本文提出组合式高功率高增益径向线螺旋阵列天线的设计思想,然后从该思想出发,针对其核心部分——矩形子阵,进行了系统的理论、模拟和实验研究,通过研究验证了该矩形子阵设计的可行性,从而拓展了高功率阵列天线的应用。高功率高增益矩形径向线螺旋阵列天线的设计思想是以组合式矩形子阵为核心,子阵采用径向线为馈电波导,短螺旋天线为辐射单元,通过耦合探针实现从径向线到单元天线的馈电：辐射单元按照正方形栅格排列在径向线顶板上,通过调节探针的结构尺寸和旋转单元天线实现单元等幅同相激励；将径向线外沿封口为正方形,通过等幅多路功分网络可以组合为更大的矩形阵,以达到提高增益的目的。基于上述思想,对矩形径向线螺旋子阵相关的基础理论进行了系统的总结和完善。主要包括：分析了阵列布局与天线性能的关系,由此获得子阵设计的轮廓参数(包括等幅同相激励和单元间距的选取范围)；分析了径向线内微波模式,给出了完整的单模传输条件,由此获得矩形子阵的设计原则(包括正方形栅格布局和馈入同轴的尺寸)；采用三短路面模式匹配技术(TPMMT)计算了探针的散射矩阵,加深了对探针耦合机理的认识,为探针的选取提供依据。通过对同轴-径向线转换器、短螺旋单元天线和耦合探针等关键环节的合理优化,对4单元矩形子阵和4路等幅径向线功分器的模型进行了优化设计,以此为基础设计了组合式16单元矩形子阵。实验结果表明该天线在3.8-4.2 GHz的频带范围内,轴向增益大于17.5 dB,口径效率大于82%,初步验证了矩形径向线螺旋子阵的可行性；但其仅在3.75-3.95 GHz的频带范围内驻波系数小于1.3,且辐射效率和轴向轴比恶化。经分析,认识到子阵各单元为同相馈电,轴向辐射时各螺旋天线相位位置相同(横杆指向一致),导致匹配不佳。针对上述不足,通过重新优化子阵阵列布局和耦合探针,改进设计了单层径向线馈电的16单元矩形螺旋子阵,其结构可以有效避免各路耦合输出的同一性,改善馈电系统和单元天线的匹配性能。实验表明,该单层16单元子阵在3.8～4.2 GHz的范围内可以实现良好的轴向辐射,辐射效率大于95%,增益大于17 dB,口径效率大于74%,轴比小于1.30 dB；通过两种16单元子阵性能的比较,推断组合式馈电更有利于实现等幅耦合,但对短螺旋单元天线的匹配性能要求很高；单层径向线馈电轴向长度短,更有利于小型化,辐射效率和圆极化程度较高。更多还原

【Abstract】 With the development of high-power microwave (HPM) technology, more attention has been progressively paid to the function of HPM antenna as the terminal of HPM system. Due to particularities of HPM, the traditional array antenna can not be used directly into HPM field due to limit of power-handling capacity of power dividers and phase shifters. Therefore, many researches have been made at home and abroad, and such HPM antennas as mode converter with radiant horn, Vlasov antenna, mode-transducing antenna and High-power radial line helical array antenna have been put forward. The antennas mentioned above have their own characteristics. By analysis and comparison we find High-power radial line helical array antenna have some special advantages, which can probably solve many problems exist in HPM radiation. But this antenna can not meet high gain because the probe coupling energy can not regulate arbitrarily. Based upon the above background, the design idea of a new assembled high-power high-gain array antenna is put forward. And then, focused on its key part——square radial line sub-array antenna, theoretical analysis, numerical simulation, and experimental research have been carried out, through which, the feasibility of the design idea of the anew assembled antenna has been proved, and the sub-array model fulfills high efficiency, small size and circularly-polarized directional radiation.The assembled high-power high-gain array antenna is combined with many square sub-array, which adopts short helical antenna which radiates circularly-polarized wave at its axial direction as radiation unit, uses radial line as feeding waveguide, applies new-type coupling probe to feed energy from radial line to unit antenna. Scheduled excitation magnitude and radiation phase can be reached by adjusting the coupling factor of the probes and rotating the radiation units, and in which way, directional radiation of microwave can be achieved.Theoretical elements related to the square sub-array antenna are summarized and ameliorated systemically based upon the basic principle of high-power radial array antenna. The Paper focuses on the far-field radiation field of rectangular array antenna, the research of basic features of radial line, the favorable radiation conditions of circularly-polarized wave conditions at axial direction of low-profile helical antenna and the three plane mode match technique is applied to model the generalized S parameters of coax-waveguide T junctions. In this way, design principles are obtained. Coaxial-line to radial-line junction, unit antenna and array arrangement, etc. are optimized rationally to make them meet requirement of the square sub-array, based on which, a helical assembled square array antenna of 16 elements using L—haped coupled probes is put forward, which is combined with 4 helical square array antennas of 4-element and a 4-way radial line equal power divider.Numerical simulation and measurement are accomplished in detail. Measured result shows that in the range of 3.75 GHz to 3.95 GHz, the directivity is upon 17.5 dB, and the VSWR is below 1.3. But due to the radiation phase of each helix is same, reflectance and axial ratio of the array is not ideal.For the disadvantage mentioned above, an improved model of 16-element helical square array antenna fed from single radial line is designed. A new type of one side post coupling probe and L-shaped probe are used to feed energy from radial line to unit antenna. The experimental research shows that in the range of 3.8 GHz to 4.2 GHz, the directivity is upon 17 dB, and the VSWR is below 1.3, the aperture efficiency is upon 74%, and the axial ratio is below 1.3 dB. Meanwhile, through comparison, and the advantages and disadvantages of the two models are analyzed.更多还原