AI-SI法分析X波段机载雷达天线罩

采用口径积分-表面积分(AI-SI)算法,对带罩机载阵列天线进行了分析。雷达罩的介质反射是引起天线方向图副瓣抬升的主要原因,在传统的AI-SI法分析天线罩过程中没有考虑天线金属阵面对天线罩介质反射的影响,因此,带来较大的计算误差。为了避免上述问题,文中在分析带罩天线过程中,采用了理想源阵列加反射板模型。天线罩总的透射场为阵列天线的一次透射场与反射板产生的二次透射场的叠加。为验证算法的正确性,将AI-SI算法计算结果与CST软件仿真结果进行了比较,两者吻合较好。     

基于天线-罩体综合设计的反射面赋形设计方法

介质夹层式天线罩在保护内部天线的同时,使得透过罩体后天线口径场的幅度和相位分布发生变化,其中相位分布的变化是引起天线远场方向图畸变的主要因素.文章从天线罩体综合设计的角度出发,提出一种反射面赋形设计方法,通过赋形反射面来改变天线口径场的相位分布,使其与天线罩引起的相位分布的趋势相反,以保证透过天线罩后的口径场仍为同相场.对某地面卫星通信站的9.14m口径天线罩进行了数值实验,结果表明:所提方法可有效改善带罩天线系统的电性能,对于方向图畸变导致的副瓣和零深变化其效果尤为显著.     

带罩导弹远场方向图数值仿真中积分域的确定

导弹天线罩是用来保护位于高速飞行的导弹前端的天线系统免受外界影响的一种装置,为研究导弹天线罩对天线性能所造成的影响,该文在运用平面波谱-表面积分法分析天线罩综合电性能基础上,详细讨论了为获取带罩导弹远场辐射方向图所采用的数值算法中的积分区域的确定。     

近远场变换中探头方向图的改进与比较

基于进一步提高国内平面近场测量中的副瓣精度,将两种新的探头H面方向图应用到近远场变换中,并与国内目前搭建近场测试系统所使用的两种探头方向图进行结果分析与比较。通过在微波暗室对某频段阵列天线测量,并分别用传统的Stratton-chu积分法、E面电场法以及边缘电流法与边缘电流逼近法进行近远场变换。结果表明,新的探头方向图应用使副瓣测试精度基本接近国际先进水平,远远优于国内现有水平,具有很强的工程实用性。     

减小平面近场测量中多次反射误差的新方法

本文给出了用平面近场技术测量超低副瓣天线时,平面近场测量总误差与天线远场方向图副瓣电平的误差方程,并进行了计算机仿真;提出了减小平面近场测量中探头天线与待测天线间多次反射误差和微波暗室电特性误差对超低副瓣天线所引入的测量误差的"自校准法",实验结果说明该方法是解决平面近场测量中多次反射和微波暗室电特性误差较为理想的方法.     

由平面波谱法求解天线罩瞄准误差的一种方法

天线罩是用来保护无线电系统免受外界影响的一种装置,为了保证在天线扫描角范围内电磁波通过天线罩时得到最大的功率传输系数和最小的相位畸变,运用平面波谱法分析天线罩对天线电磁性能的影响,采用数值积分法求得远区方向图,结合优化方法求解出瞄准误差.     

基于曲面口径积分/几何光学的天线罩混合分析

提出了发射模式下，曲面口径积分／几何光学的混合分析方法。利用等效原理，将天线罩内表面上的反射场等效为面电流和面磁流，沿等效源所在曲面作口径积分，确定二次入射到罩壁上的入射场，经过局部平面的多层介质传输到天线罩外表面，在外表面上将一次传输场和二次反射场矢量叠加，对外表面切向场的表面积分得到天线带罩系统的远场方向图。该方法解决了发射模式下一次传输场和二次反射场的矢量叠加问题，计算精度高；仿真预测结果均为试验所证实。     

天线频选罩的隐身特性研究

针对在军工装备上日益重要的雷达天线频率选择表面(frequency selective surface, FSS), 分析了FSS雷达散射截面积(radar cross-section, RCS)的特征, 以及和金属表面RCS的区别, 并澄清了产生这种差异的内部机理, 为改善FSS天线罩以及类似腔体的RCS提供了理论指导和解决问题的思路和方法.首先从理论上分析了覆盖频选表面的雷达腔RCS的产生机理, 然后用全波严格仿真算法计算了不同雷达腔RCS的数据, 并结合内部场图认证了前面的理论分析结论.理论和仿真分析表明, 频选带外的高反射特性并非像金属表面那样完全反射电磁信号, 必须考虑频选天线罩的透射和罩内的腔体效应导致的电磁波能量聚集和二次辐射, 这些因素对覆盖频选雷达腔体的RCS产生很大的影响.最后, 提出了一种利用吸波材料减少腔体谐振效应和能量汇聚从而改善频选罩RCS的方法, 取得了良好的效果, 在大部分频段, 该方法使RCS改善达10 dB以上.     

多层天线罩的电性能分析

论述了几何光学-射线跟踪法分析天线-天线罩系统的电性能，并将网络思想融入其中，简化多层天线罩电性能分析，并给出了远场辐射方向图和透波率的仿真结果，结果说明此方法简单有效，在多层罩的分析中更有效率，而且精度良好。     

基于高斯积分的平面波谱法分析天线罩电性能

将平面波谱表面积分法与高斯积分相结合分析天线罩的电特性。在计算了口径天线的差波谱以求解带罩天线差方向图的基础上,将高斯积分应用到由罩外表面切向场求远场方向图中,提高了平面波谱法的计算精度。最后通过具体算例表明了本文方法的有效性。     

频选膜拼接工艺误差对复材天线罩电性能的影响

加载频率选择表面(FSS)薄膜的复合材料天线罩在实际制作过程中,需将若干FSS薄膜结构进行拼接以构成一个整体,FSS膜的拼接工艺误差则对天线罩的电性能产生实质性的影响。文中设计了一款X波段的A夹层平板复合材料天线罩,并建立了由拼接工艺误差带来的FSS膜搭接和FSS膜缝隙的电磁仿真模型,研究了不同拼接工艺对复合材料天线罩的透波率、电磁波传输特性的影响以及对天线辐射特性的影响。研究结果表明：天线罩中的FSS薄膜结构的拼接错位对电磁波传输影响明显,会明显降低天线主瓣增益和天线罩透波率;当入射电磁波的极化方向与FSS薄膜结构的搭接缝方向相同时,FSS膜结构对天线罩透波率影响较大,当极化方向与FSS薄膜结构的搭接缝方向垂直时,则其对天线罩透波率影响较小;两块FSS膜结构边缘搭接的相对位置和搭接距离对天线方向图有明显影响;两块FSS薄膜结构边缘无搭接且存在缝隙则对天线罩透波率影响较小。该研究对复合材料天线罩的制造工艺具有工程指导意义。     

金属雷电分流条对雷达罩电性能的影响分析

论文建立了天线罩分流条电磁传输研究模型,通过仿真和实验,对比分析了雷电分流条的电磁波传播特性,特别研究了中空十字型和十字型金属分流条的电磁波传输机理,以及金属分流条的材料、长度、宽度、厚度和电磁波不同入射方向对雷达罩电磁波传输性能的影响。研究结果表明:十字型金属雷电分流条对天线罩的电磁传输影响严重,而设计合理的中空十字金属分流条可以有效传输电磁波;另外,金属分流条的厚度和常用金属材料对电磁波传输影响不大,主要影响其导电能力和重量;在保证天线罩雷击安全的前提下,调整金属条长度可以使天线罩电性能达到最佳;金属条的宽度对电磁波传输性能影响明显,宽度越大,天线远场方向图主瓣增益越大;随着入射角的增大,方向图主瓣增益在减小,入射角超过30°时,雷电分流条对天线罩的电磁传输为负影响。     

Fully Probe-Corrected Near-Field Far-Field Transformation Employing Plane Wave Expansion and Diagonal Translation Operators

Near-field antenna measurements combined with a near-field far-field transformation are an established antenna characterization technique. The approach avoids far-field measurements and offers a wide area of post-processing possibilities including radiation pattern determination and diagnostic methods. In this paper, a near-field far-field transformation algorithm employing plane wave expansion is presented and applied to the case of spherical near-field measurements. Compared to existing algorithms, this approach exploits the benefits of diagonalized translation operators, known from fast multipole methods. Due to the plane wave based field representation, a probe correction, using directly the probe's far-field pattern can easily be integrated into the transformation. Hence, it is possible to perform a full probe correction for arbitrary field probes with almost no additional effort. In contrast to other plane wave techniques, like holographic projections, which are suitable for highly directive antennas, the presented approach is applicable for arbitrary radiating structures. Major advantages are low computational effort with respect to the coupling matrix elements owing to the use of diagonalized translation operators and the efficient correction of arbitrary field probes. Also, irregular measurement grids can be handled with little additional effort.     

Finite element analysis of axisymmetric radomes

A two-step technique for the analysis of axisymmetric radomes is presented. Initially, an axisymmetric finite-element approach is employed, together with an absorbing boundary condition for mesh truncation, to determine the near fields scattered by an empty radome illuminated by a distant source. Next, the reciprocity theorem is invoked to determine the far-field pattern of an antenna encased by the radome, by computing the interaction between the current distribution on the antenna and the near-field data determined in the first step. The details of the formulation are presented along with numerical results for two different arrays enclosed by radomes of varying permittivities     

Application of spherical wave expansions to reflector antennasusing truncated field data

The electromagnetic field radiated by paraboloidal and hyperboloidal reflector antennas excited by an azimuthally independent, linearly polarized source is considered. The electromagnetic field is sampled on a spherical surface in order to numerically generate a set of spherical wave mode coefficients which, in turn, are used to compute antenna patterns. Patterns are produced in the near- and far-field regions based on both full and partial, or truncated, near- and far-field data as a function of the antenna parameters and the truncation angle location. The similarity of the patterns obtained from truncated field data to the untruncated patterns is found to depend on the pattern level at the truncation point, the location of the truncation point, the antenna parameters, and the radial distance between the spherical surfaces on which the electromagnetic field is sampled and produced     

Hybrid PO-MoM analysis of large axi-symmetric radomes

Over the last three decades, intensive work has been done to develop techniques aimed at accurate and efficient analysis of antenna radome systems. Some applications involve radar operating in the millimeter wave range and for those cases the radome size can be on the order of one hundred wavelengths or so in length. For practical simulations of such large radomes, a hybrid physical optics-method of moments (PO-MoM) technique is presented for accurate and efficient analysis of electrically large radomes. The procedure combines the method of moments (MoM) for modeling the tip region of the dielectric radome and ray optics in conjunction with physical optics (PO) for treating the flatter smooth section of the radome. Calculated far-field patterns using the new technique agree well with measured data for a reflector antenna radiating in the presence of a large radome. The computational time for simulating the performance of a 46λ reflector in the presence of an 88λ long radome was a mere 4 h on a 233 MHz PC     

High-gain backup antenna design for Pioneer Venus Orbiter spacecraft

The development and performance is described of a high-gain antenna designed to serve on the Pioneer Venus Orbiter spacecraft as a backup to the principal high-gain antenna unit in the unlikely event the mechanically despun antenna mechanism malfunctioned. The final design, a center-fed standing wave array of six sleeve dipoles enclosed in a fiber glass radome, performed successfully, as did all the antennas, on the Pioneer Orbiter spacecraft which was launched on May 20, 1978, as part of the Pioneer Venus mission. Photographs of experimental models giving details of design and construction are included, as well as graphs showing measured pattern and impedance matching characteristics of the subject antenna.     

大型机载雷达罩对线阵天线影响的分析

提出了一种口径积分-表面积分和射线跟踪混合方法,分析了某大型雷达罩对SSR线天线及单元方向图的影响,给出了带罩天线方向图中直射瓣和反射瓣的矢量合成的解法,数值计算结果与实验数据符合较好.