共查询到19条相似文献,搜索用时 328 毫秒
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<正> 前言各种各样的反射器,早已用作增强小船的雷达检测方法和雷达反射特性比较差时的导航辅助手段。其中,广泛使用的是角形反射器。然而,目前已为龙伯透镜反射器所代替。因为,龙伯透镜具有较大的雷达截面积和宽角反射特性。尤其,对于全向雷达反射器,小型船舶和导航方面 相似文献
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1973年11月20日IMCO通过了A277(Ⅷ)号决议,建议各国行驶在海洋中的各类舰艇船舶上应架设雷达反射器。球形介质透镜反射器是用得最普遍的一种雷达反射器。本文详细介绍了球形介质透镜反射器设计的一些问题:诸如龙伯透镜的介质折射率、分层透镜各部分介电常数的确定、雷达反射器的有效反射截面积的计算公式以及制造工艺等。这方面的有关资料可分别在不同的书藉、杂志、会议录和专刊中找到,作者作了系统性的整理,有关公式也已作过认真的推导,还更正了某些错误。 相似文献
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一、前言许多设计原则在电磁频谱中的微波和光学二个领域中是通用的。因此,很多用以设计透镜和反射器的光学方法,已经被用来把微波辐射聚集成定向波束。龙伯透镜却是一个例外,它的实际应用只局限在微波领域。其原因在于这球形透镜以径向对称的方式要求非均匀的折射率分布。在微波频段,龙伯透镜已经用两种 相似文献
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测量雷达反射器和各种物体的反射特性,或对雷达装置的性能进行评价和试验时,利用一个可自由改变雷达截面的标准雷达反射器是非常方便的。这种雷达反射器以前虽曾有过几种形式,但因皆属利用金属面反射的方式,故反射效率低,不太实用。本文介绍的雷达反射器,利用了龙伯电磁透镜的聚焦特性与球对称性,因而反射效率高,并能随着透镜旋转角的变化,线性地改变雷达截面,实用价值较高。本文首先提出了获得这样一种雷达反射器的方法,接着给出了其设计和制作方法,并在此基础上,通过试制和实验证实了实现此种方案的可能性。以本文试制的由直径30.5厘米的龙伯电磁透镜构成的雷达反射器为例,当工作在频率为9375兆赫的水平极化波时,可使雷达截面从42.28m~2变化到0.42m~2。 相似文献
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本文提出了一种利用多个龙伯透镜单元组成的低剖面阵列天线,天线可实现大角度波束扫描。从仿真结果可见,与传统相控阵天线相比,波束扫描范围可扩展到±71°,与具有相同口径面积的基于单个龙伯透镜实现的阵列天线相比,剖面高度和体积重量大大降低。 相似文献
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龙伯透镜分层介质球的设计与计算 总被引:1,自引:0,他引:1
陈静 《光电对抗与无源干扰》1997,(1):1-5
本文对龙伯透镜分层介质球进行分析和计算。对设计中的主要问题进行了论证,给出计算实例和制造方法。 相似文献
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设计并实现了一种V频段圆柱龙伯透镜天线.在平行平板波导间,根据龙伯透镜原理与介电常数等效原理,推导出了圆柱龙伯透镜天线的理论设计公式,并结合商业仿真软件高频结构仿真器(HFSS)仿真分析和优化,完成天线设计.仿真结果表明,该V频段圆柱龙伯透镜天线增益为21.4 dBi,波束宽度为1.56o,副瓣电平为-14.7 dB.根据设计结果,加工和测试验证V频段圆柱龙伯透镜天线的可实现性,实测结果表明,该天线增益为20.1 dBi,波束宽度为1.60o,副瓣电平为-11.1 dB,天线效率为45.7%,说明该天线具有一定的工程应用价值. 相似文献
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Two families of spherically symmetric dielectric lenses are considered. Their optical properties are studied, and the radial eigenfunctions describing the electromagnetic field inside the lenses are found in terms of hypergeometric functions. Among the members of these two families are the Luneburg lens, the Maxwell fisheye, the isotropic lens of Eaton, and a lens that behaves like a metal reflector. 相似文献
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Permittivity of composites used for Luneburg lens antennas by drilling holes based on 3-D printing technique 下载免费PDF全文
DONG Changsheng CUI Ziqing LI Yong WANG Haidong JIN Chao YANG Shiwen 《太赫兹科学与电子信息学报》2017,15(4):646-651
Due to the attractive performances such as the ability of beam focus, broadband, multi-beam scanning and other features, Luneburg lens antennas are applied in multi-beam antenna, which overcomes the problem of gain loss produced by multi-beam parabolic antenna. Based on 3-D printing technique, Luneburg lens antennas by drilling holes are studied. Permittivity and loss tangent of the equivalent lens materials can be influenced by original materials, hole shapes, hole directions, and porosity. After tests, polystyrene with waxes may be the most appropriate materials for Luneburg lens with high strength. Permittivity with the shape of triangle is the lowest due to the homogeneity. Relative permittivities with the direction at a range of 15°-45° are lower while loss tangent at a range of 0°-30°. Radial directional holes are more appropriate for Luneburg lens. The relative permittivity is decreased with the increment of porosity. After calculations, the forecasts calculated by Looyenga and A-BG theory are more precise. Finally, Luneburg lens with two layers is fabricated by 3-D printing. 相似文献
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用矢量球面波理论和互易原理分析伦伯透镜天线 总被引:2,自引:0,他引:2
伦伯透镜是一种球形分层介质天线,考虑到数值计算的复杂性,本文提出用矢量球面波理论和互易原理相结合,分析其性能。该方法首先用矢量球面波理论计算平面波入射到多层介质球的散射场,在此基础上,用互易原理将散射场转变成天线的远区辐射场。基于这种方法,木文着重研究了伦伯透镜天线的焦区场和远区场特性,包括透镜分层总数以及层与层之间存在的空气间隙对实际应用可能造成的影响。最后。对卫星通信中伦伯透镜天线多波束应用的可行性给出了分析结果。 相似文献
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Design optimization of radially nonuniform spherical lens antennas is the focus of this paper. In particular, special attention is given to the optimal design of nonuniform Luneburg (1964) lens antennas. One of the important engineering objectives of designing an optimal Luneburg lens antenna is to use as small number of shells as possible while maintaining an acceptable gain and sidelobe performance. In a typical radially uniform design, by reducing the number of shells, the gain is decreased and the grating lobes are increased. This deficiency in the radiation performance of the uniform lens antenna can be overcome by designing the nonuniform lens antenna. This necessitates the optimum selection of each layer thickness and permittivity. A genetic algorithm (GA) optimizer with adaptive cost function is implemented to obtain the optimal design. In this manner, the GA optimizer simultaneously determines the optimal material and its thickness for each shell by controlling the gain and sidelobes envelope of the radiation pattern. Various lens geometries, including air gaps and feed offset from the lens surface, are analyzed by using the dyadic Green's functions of the multilayered dielectric sphere. Many useful engineering design guidelines have been suggested for the optimum construction of the lens. The results have been satisfactory and demonstrate the utility of the GA/adaptive cost-function algorithm. Additionally, the radiation characteristics of a novel two-shell lens antenna have been studied, and its performance is compared to the Luneburg lens 相似文献