【作者】 陈腾博；

【导师】 焦永昌；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 为适应卫星通信发展的需求,卫星通信系统要求星载天线不仅能够生成高质量的点波束,而且需要具有在其服务区内进行快速灵活的波束扫描的能力。本文密切结合预研项目“星载多波束及可控点波束天线”,研究了星载天线阵列馈源的分析和设计。作者的主要工作和创造性成果可概括为以下几个方面:1.对馈源阵列的组成单元形式进行了研究,根据工程设计提出的双频段工作、易于实现圆极化收发和天线方向图圆对称性较好等要求,分别设计了螺旋天线、阿基米德平面螺旋天线和光壁圆锥喇叭天线。采用电磁仿真软件对天线进行了仿真计算,得到在要求频段内各天线的电性能参数。设计了一种低副瓣轴向模螺旋天线,仿真分析和实验测试结果说明在要求的频带范围内该天线驻波比小于1.15,天线方向图的最大副瓣电平低于-25dB。提出了一种双频段工作的光壁圆锥喇叭天线的设计方法,该天线具有良好的双频段工作特性以及较高的增益,可满足卫星通信的需要。2.对阵列馈源的综合方法进行了详细分析,研究了非线性最小二乘法和粒子群(PSO)算法。阐述了解决非线性最小二乘问题常用的两种方法:Gauss-Newton法和Levevberg-Marquardt法。通过对一个实际最小二乘问题的求解,研究了非线性最小二乘法的算法流程和主要优缺点。对粒子群算法进行了深入的研究,针对标准粒子群优化算法的一些缺陷,提出了一种改进型粒子群算法。该算法有效地解决了粒子群早熟收敛和搜索精度不高的缺点,通过对检验函数进行数值计算并与其它改进型粒子群算法进行比较,说明本文提出的新型粒子群算法的优越性。3.对阵列馈源的馈电网络进行了研究。提出了多波束形成、波束隔离、波束扫描控制、收发双工和双频双圆极化的设计方法。在分析过程中,采用了电磁场辐射理论、微波网络理论、波导模式理论、滤波器理论和工程最优化理论,对馈电网络的部件进行了优化设计。设计了双频双圆极化器、正交模耦合器、窄带滤波器等元件,仿真分析结果说明文中设计的馈电网络可以实现双频双圆极化收发,上下行信号之间的隔离度大于70dB。4.研究了星载天线阵列馈源的阵列综合设计。分析了几种阵列排阵形式,包括六边形阵列、圆环阵列等阵列结构形式。分析了阵列单元在阵列中的位置以及幅相分布对馈源阵列辐射方向图的影响,以上述的各个参数为设计变量,采用粒子群算法对阵列进行优化综合,在0°～360°方位角任意截面上都能得到理想的赋形方向图包络,设计结果表明六边形阵列馈源可以在双频段工作。对在所要求角域内阵列馈源的波束扫描进行了分析,列出了波束指向不同扫描角时的辐射方向图以及阵列单元的控制相位。文中还设计了一个平面二维天线阵列,阵列天线方向图的远场测量结果与优化综合得到的天线方向图非常逼近。该章最后将馈源阵列与标准侧馈双反射面天线结合起来进行一体化设计,通过仿真计算得到较好的远场辐射特性。5.研究了馈源阵列单元之间的互耦效应对阵列辐射特性的影响。互耦效应的存在使得每个阵元的方向图与其在阵中的位置有关,波束形状各不相同。文中借助仿真软件对阵列天线进行仿真综合,得到单元之间的互阻抗矩阵,计算出阵列馈源单元的有源散射系数。当优化综合得到天线的最优化幅相分布后,可以通过对散射系数矩阵求逆得到需要的单元入射电压幅值。6.讨论了馈源阵列的容差分析,通过微扰法对各个组成部分进行检验,尽可能将设备精度和环境因素对馈源电特性的影响降至最低。采用概率论的方法,分析了馈电网络的随机幅相误差和量化幅相误差对天线增益、副瓣电平和波束指向等参数的影响,并计算了在不同量化误差时,馈源阵扫描状态下的方向图,得到了移相器和衰减器的精度对馈源方向图的影响。更多还原

【Abstract】 To meets the demand for the developments of satellite communication, satellite-borne antennas are required not only to produce spot beams with high quality, but also to have the flexible ability of beam scanning in their service region. Related tightly to a Pre-research project entitled "Multi-Beam and Steerable Spot Beam Antennas for Satellite", this dissertation presents a systematic investigation into the analysis and design of the array feed for the satellite-borne antenna. The author’s major contributions on the subject can be summarized as follows:1. First the elements of the array feed are investigated. According to the design requirements such as dual band, receiving and transmitting circular polarization as well as symmetrical pattern in azimuthal angles, the spiral antenna, Archimedes plane spiral antenna and conic horn antenna are studied in detail. Simulations of these antennas are carried out by the electromagnetic simulation software, and the desired electrical performance can be achieved. A low sidelobe single wrap helical antenna is also presented, and its simulated and measured results are provided. These results show that for interested band, the VSWR of the antenna is less than 1.15 and its sidelobe level is less than -25dB. A dual band conical horn antenna is designed, which operates in dual band with high gain and meets the demands of satellite communication.2. Synthesis methods for the feed array, including the nonlinear least square method and the particle swarm optimization method, are investigated. The computational processes of the Gauss-Newton method and Levenberg-Marquardt method are introduced. The search routine and the convergence characteristics of the nonlinear least square method are shown by solving a practical problem. Especially the particle swarm optimization (PSO) algorithm is investigated, and the standard PSO algorithm is modified in some aspects in order to overcome some disadvantages, such as low efficiency and premature convergence. As r result, a new PSO algorithm, named the crossed PSO (CPSO) algorithm, is proposed. Simulation results show that the crossed PSO is superior to other kinds of PSO algorithms and can be used to solve a wide range of problems.3. Feed network of the array antenna is discussed. Techniques of electrically realizing multi-beam, beam isolation, beam-scanning, receiving and transmitting duplex, dual-band dual-circular-polarization are introduced. Main components of the feed network, including dual-band dual-circular polarizer, the orthogonal mode transducer (OMT), and the narrow band filter are presented. The electro-magnetic radiation theory, the microwave network theory, the wave-guide mode theory, filters theory and optimization are used for the design of the feed network. Simulation results show that with this feed network, the dual-band dual-circular-polarization can be achieved. The isolation between these two bands is more than 70dB.4. Synthesis of the array feed is addressed. Several kinds of array structures, including hexagon array and circular array, are introduced, and the CPSO algorithm is used to design such kinds of antenna array. The parameters affecting the array patterns, such as the amplitude and phase of the elements, the spaces between the elements as well as the positions of the elements in the array, are optimized in order to make the array pattern approach the desired pattern on each section of all azimuthal angles. Meanwhile, the dual frequency hexagonal array antenna is optimized. The scanning characteristic of the array feed is also analyzed. The scanning patterns of the array in the required region and the excitation phase of each element are presented. A hexagon antenna array is designed and measured. Measurement results show that for the interested band, the array patterns approach the desired patterns very well. A side-fed offset Cassgrain antenna with the array feed is analyzed. Simulation results show that this antenna system meets the engineering requirements.5. The mutual coupling effect between the elements in the array is analyzed. Patterns of the elements in the array are different because of the mutual coupling effect, which are related to the element locations in the array. The S-parameter matrix and mutual impedance matrix are also calculated. The optimal amplitude and phase of elements are given, and then the incident voltages can be achieved by solving the inverse of the S-parameter matrix, thus the mutual coupling effect can be reduced.6. Tolerance analysis of the array feed is introduced. The components of the system are analyzed by using the perturbation method, and the effects of the equipment precision and the environmental factor on electrical characteristic are reduced as much as possible. The effects of the stochastic and quantification error on the antenna gain, the sidelobe level and the beam direction are then analyzed by the probability theory. The scanning patterns of the feed array under the different quantification error are analyzed, and effects of the digital phase shifter and the attenuator on the array pattern are also discussed.更多还原