共查询到19条相似文献,搜索用时 281 毫秒
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随着干扰的日益增多,卫星阵馈反射面赋形波束天线通常希望具有尽可能低的旁瓣电平。然而,当馈元阵口径面面积有限时,窗口效应往往会使这种天线具有较高的旁瓣电平。本文在阵馈反射面天线频域方向性相乘原理的基础上,对这种窗口效应形成的原因和产生的影响进行了分析,并提出了两种能够减小这种窗口效应的窗口函数,最后用一个实际阵馈反射面天线的仿真计算结果证明了这两种窗口函数的有效性和优越性。 相似文献
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随着有源相控阵和数字波束形成技术的应用, 低轨道卫星通信多波束阵列天线不仅可以形成同时多个固定的对地等通量低旁瓣赋形波束, 还具备了可以随着通信任务需求变化, 动态调整方向图形状的能力.但是目前常用的高性能波束赋形算法, 运算量较大, 收敛速度慢, 优化参数调整复杂, 无法直接应用于在线实时计算.针对上述要求, 提出了一种高效的迭代最小方差方向图综合方法.该方法采用方向图分区域加权逼近和方向图相位去约束技术, 在满足较高的主瓣赋形精度和旁瓣电平控制等指标要求的前提下, 具有迭代过程简单、优化参数少、算法稳健和运算量少等特点, 可以部分满足要求波束方向图动态变化的卫星通信系统权重系数在线计算的需要. 相似文献
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卫星波束赋形天线普遍采用阵馈抛物反射面天线和单馈成形反射面天线。针对前者阵馈和后者反射面表面开头复杂的特点,本文分别采用了遗传算法和共轭梯度法对这两种天线进行了优化,并获得了中国版图的减束赋形,说明上述算法在卫星反射面天线波束赋形优化中是有效的。 相似文献
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基于自适应理论,在满足一定准则的条件下,通过寻求一组合理的权值,可以有效地实现对主波束的赋形和旁瓣电平、零陷点位置及深度的控制。通过算例可以证实这种算法对任意排布的阵列,无论是均匀线阵、非均匀线阵还是平面阵,均能实现良好的波束赋形效果。 相似文献
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为提高反射面天线的照射均匀性,利用波束赋形技术设计一款工作在15 GHz的高性能偏置反射面天线.该天线由一个非均匀有理B样条(non-uniform rational B-splines,NURBS)反射面和一个介质棒馈源组成,NURBS反射面通过物理光学法结合Nelder-Mead优化算法来赋形,从而获得理想的天线辐射场.仿真结果表明,赋形后的反射面天线相对旁瓣电平低于-20 dB,增益在-2.7°~2.7°的波束范围内超过20 dBi,且浮动不超过1 dB.该天线具有结构简单、旁瓣低、增益均匀的特点,在卫星通信等领域具有重要作用. 相似文献
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为了实现一种具有高口面辐射效率、斜波束出射能力的口径天线,采用几何光学方法设计了一种偏馈双反射面天线.天线主反射面采用赋形设计,副反射面的设计过程中采用Snell定理作为约束条件.通过理论公式、数值模拟仿真和实验测试研究,实现了一种出射波束口径为110 cm、天线口面场分布为抛物形分布、波束出射方向与竖直方向成20°夹角的赋形偏馈双反射面天线.在中心频率95 GHz下,实测天线增益为59.7 dB,第一副瓣电平为-19dB,天线口径效率达到78%. 相似文献
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Optimum beam scanning in offset single reflector (paraboloid) and dual reflector (Cassegrain and Gregorian) antennas is considered. Analytical, computationally efficient solutions and results are presented for the optimum feed position, the constant beam direction feed loci, and the optimum feed position locus. Examples are presented to verify that the analysis technique yields the optimum feed position, which exhibits better gain, pattern symmetry, and sidelobe levels when compared with other feed positions producing beams scanned to the same direction. The solutions described were obtained under the ray optics approximation and a "receive mode" analysis. Although the developed method was applied to the antennas listed above, it can be easily extended to othern -reflector systems, shaped reflector antennas, lenses, and other similar systems. 相似文献
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Yi-Xi Zhang Jun-Mei Fu Wen-Bing Wang 《Microwave and Wireless Components Letters, IEEE》2004,14(7):328-330
In this letter, array-fed reflector or lens antennas are proven by using Fourier analysis methods to follow a kind of frequency-domain principle of pattern multiplication, which states that the spectrum of the composite field of such an antenna is the product of the spectrum of the far field of the individual spot beam and that of the excitation coefficient sequence. This principle will provide a useful and efficient tool not only for determining the optimum excitations but also for predicting the antenna performance. 相似文献
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A. G. Roederer 《电信纪事》1984,39(1-2):34-43
Three telecommunication satellite antennas, developed under the research and development programme of the European Space Agency, ESA, are described. The first one, operating around 1.6 GHz, is to equip advanced mobile communications satellites. It includes an 8 m unfurlable reflector and a system of multiple feeds. The influence of facets in the mesh reflector surface on the radiation patterns is discussed. The second one, for European coverage in the 10.7 to 11.7 GHz band, includes a 1.1 m offset reflector fed by 23 horns backed by a numerically machined waveguide distribution network. Performances of the antenna, with emphasis on the distribution network, are discussed. The third antenna, operating at 19 GHz, generates 0.25° low sidelobe spot beams to cover major European traffic centers. Its 4 m offset Cassegrain reflector is fed by a system of about a hundred horns. Each beam originates from a cluster of seven horns, some clusters, corresponding to closely adjacent beams, partially overlap. The design and performances of the antenna and its components are discussed in the paper. 相似文献
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An investigation into the multiple-beam capability of offset antennas using circularly symmetric main reflectors is described. The efficiency and sidelobe performance of systems designed to produce beams up to 4.6° either side of boresight with reflector diameters ranging from 100 to 300 wavelengths are shown to make the antennas suitable for multiple-satellite-access earth stations. Comparison is made with a nonsymmetrical main-reflector antenna designed for the same requirements. 相似文献
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John R. Forrest 《电信纪事》1984,39(1-2):69-75
The anticipated density of satellite communications traffic with mobiles will require multi-beam earth coverage. Multiple beams can be generated from reflector antennas with multiple feeds or from a phased array aperture. The constraints on each system are discussed, and it is concluded that for more than about seven beams the best system involves a phased array antenna, particularly if reconfigurability of the beams may be required. Active phased arrays, with a power amplifier at each radiating element offer advantages in reliability and may indeed be the only way of handling the large total radiated power of future systems at acceptable levels of intermodulation. 相似文献
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Sudhakar Rao K. Morin G.A. Tang M.Q. Richard S. Kwok Kee Chan 《Antennas and Propagation, IEEE Transactions on》1995,43(10):1036-1047
Design and experimental results of a wide-angle coverage 45 GHz multiple-beam antenna for military satellite communications are presented in this paper. The high-gain spot beams with low sidelobe levels and efficient adjacent beam overlap are generated by employing an offset parabolic reflector with overlapping feed clusters. The beam shape can be adapted to cancel either single- or multiple-jammers by varying excitations within the feed cluster corresponding to the beam. Development of antenna components including Potter horn, polarizer, phase-amplitude controller, and beamforming network is discussed. Measured results of the demonstration antenna have shown that sidelobe and crosspolar levels of better than -25 dB are achieved for beams scanned over an eight-degree diameter circular coverage region. The adapted patterns of the antenna agree well with the computations, and null depths of better than 30 dB have been realized over a 4.5% bandwidth 相似文献
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Single shaped reflector antennas for broadcasting satellites 总被引:1,自引:0,他引:1
For future direct broadcasting satellites in Japan, precisely contoured beam antennas will be required for onboard antennas. Single shaped-reflector antennas are suitable for that purpose, since they do not need complex feed networks. However, in a previous study, discontinuities in the reflector surface were observed. The problem of the discontinuity was circumvented in this work and the shaped reflectors were successfully designed to produce contoured beams for covering the Japanese islands for the downlink and feederlink antennas. The downlink antenna was fabricated, and the radiation pattern was verified by measurement. The radiation pattern meets the radio regulations imposed on the onboard antenna, such as sidelobe and cross-polarization characteristics 相似文献
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When designing a dipole 'panel', a unit building block for a TV transmitting dipole array, there are several constraints which need to be met viz. beamwidth, sidelobe levels, front to back ratio and input impedance. Theories on reflector backed dipole arrays have so far dealt with idealised or thin dipoles and with infinite reflector. They are not very useful for predicting sidelobe levels and front to back ratios nor would they be of any use to calculate the input impedance of an array of relatively thick dipoles which are often used in practice. Experimental procedures are usually employed by the designer and these have proved to be very time consuming. 相似文献