天线罩去极化效应及其补偿

天线罩在对天线起到保护作用的同时,也导致了线极化电磁波通过它时必将产生的去极化效应,从而大大影响了通信质量,这主要是因为天线罩对垂直极化分量和平行极化分量的传输系数不同所致。为提高通信系统的交叉极化隔离度,更好地进行通信,对天线罩去极化效应进行了计算,根据计算结果进行了仿真,并设计了补偿电路。结果表明,通过该方法补偿后,能有效提高通信系统的交叉极化隔离度,减少天线罩去极化效应对通信的影响。     

基于近场场图的带罩天线近副瓣畸变分析

采用FEKO软件仿真带罩天线远场方向图和近场场图, 采用近场场图分析远场方向图近副瓣畸变的原因.仿真过程中采用等效源技术, 兼顾仿真精度和仿真效率.带罩天线方向图近副瓣畸变主要是由天线罩尖部区造成的, 近场场图表明三种效应导致近副瓣抬升:其一, 电磁波经过天线罩尖部发生明显的衍射, 波阵面分叉; 其二, 金属雨蚀头被激励出表面电流, 进而产生二次辐射; 其三, 部分电磁波能量经反射后透过天线罩尖部区域, 反射-透射电磁波能量叠加在副瓣方向上.针对上述效应, 对天线罩改进设计, 改进后可明显抑制带罩天线近副瓣的抬升.近场场图分析方法揭示了天线罩局部细节和远场方向图之间的联系, 对天线罩电性能优化设计有很好的指导作用.     

An experimental radome panel evaluation

Modern antenna radomes are made of materials that tend to shed water to minimize their RF attenuation when wet. The microwave performance of these materials has been studied experimentally. Radome attenuation was measured as a function of frequency, rain rate, rain incidence angle, RF incidence angle, and polarization. The tests were performed on (1) new, clean radome panels, (2) used, dirty radome panels, (3) cleaned, used radome panels, and (4) panels treated with hydrophobic paint. The results show weak loss dependence on frequency over the 13-20 GHz frequency range of interest, which increases slowly with rain rate from 2.5 to 29 mm/h except for surfaces that are wettable, where the dependence on rate is much stronger. Loss is nearly independent of rain incidence angle, but it is strongly a function of surface condition. Hydrophobic paint is shown to be very effective. The test setup used, limitations imposed by the real world, and a simplified model of radome loss derived from the test results are described     

雷达薄壁天线罩的密封及防护

探讨了雷达薄壁天线罩的密封及防护问题,介绍了天线罩材料的老化性能和常用密封胶的性能及特点,针对平面阵列中薄壁天线罩的特点进行了密封设计及密封胶的优选,确定了单组份聚氨酯密封胶胶层厚度与固化时间的关系,并通过专用底处理剂及含氟涂料的使用,提高了密封胶的粘接强度及天线罩的防老化性能.     

A microwave radome performance verification gauge

A microwave radome gauge (MWRG) design for verification of the microwave properties of a radome is presented. A mathematical model of the gauge is developed, and expected results are calculated and compared to measured results. These results indicate that the MWRG is relatively insensitive to its flange (choke) dimensions and the radiation resistance of the slot antenna formed by the flange and conducting foil that enclose the radome. The resonant frequency of the device shifts ≈0.1% for a 1% change in the radome's core thickness, or dielectric constant, and ≈0.01% for a 1% change in sheet thickness. The tool is virtually insensitive to a change in loss tangent of radome sheet material. Use of the MWRG shows that this test procedure is a satisfactory method of verifying an RF window's performance prior to shipment and installation with the antenna assembly. Experience with the measurement of standard panels indicates consistency in manufacturing and of the test method and equipment. The MWRG has also demonstrated its ability to detect defects in the RF window; that is, it accurately located bleeder strips and overlap areas between adjacent sheets     

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。     

The radiation pattern of an array of dipoles in a dielectric slab

By using the reciprocity theorem, simple expressions are derived for the far-field patterns of normal and parallel dipoles in a plane dielectric slab. The dielectric slab may have a conducting ground plane on one surface. Numerical results are presented in a graphical form to show the effects of the dielectric on the antenna pattern. A dipole array embedded in a radome occupies less space than a conventional parabolic antenna, and the ground plane offers structural support for the radome.     

曲面频选天线罩电性能设计研究

针对现如今频率选择表面(FSS)普遍基于平板进行理论研究的现状,提出了一种基于HFSS-Matlab创建曲面频率选择表面的方法。设计了平板频选单元及A夹层平板天线罩,并进行了仿真分析;采用该方法将准周期排列的曲面频选单元附于A 夹层正切卵形介质天线罩表面。为了验证曲面频选的性能,选用宽波束的平面螺旋天线作为激励,对曲面频选天线罩天线系统进行了联合仿真,并分析了加载曲面频选结构对天线罩电性能的影响。结果表明,所设计的曲面频选结构与平板FSS结构电磁性能基本保持一致,实现了曲面FSS 频率选择的功能,在传输段内不仅能够满足天线罩电性能设计指标要求,而且能有效降低天线带内强镜面反射(RCS),对曲面频选天线罩的实际工程应用具有指导意义。     

一种基于超材料的谐波抑制天线罩

设计了一种基于超材料结构的前置谐波抑制单元天线罩,该天线罩采用多层互补型亚波长单元结构,在一个天线单元的有限尺寸范围内排列更多的周期单元,减小边缘效应的影响,天线罩总厚度小于5 mm,通过PMI泡沫与喇叭天线连接。采用激光刻蚀工艺制备了不同尺寸的两种试验件,并进行了超材料的传输系数测试以及带罩天线阵谐波抑制性能测试,结果表明,所设计的超材料谐波抑制天线罩具有带内0.3 dB 的插损,二次谐波20 dB和三次谐波30 dB的抑制能力。     

面向高铁卫星通信系统的高性能天线罩设计

设计了一款适用于高铁平台卫星通信相控阵天线的高性能天线罩.该天线罩针对载体应用环境，设计了双向对称、低剖面的气动外形，以满足载体高速双向对开时低空气阻力的要求；同时根据卫星通信相控阵天线波束扫描的特点，设计了变厚度夹层结构，以实现天线罩对任意极化方向的电磁波宽角入射时高透波率的电性能.以Ku频段为例，根据设计结果进行了实物制作和测试验证，测试结果显示在10.5~13 GHz频率范围内，采用垂直极化波和水平极化波分别照射时，天线罩在0~70°的入射角范围内，透波率均保持在80%以上，同时天线罩对相控阵扫描波束的指向误差维持在±0.5°范围内.     

复射线理论应用于天线一体化设计

分析自由空间天线辐射特性的方法已十分成熟,如口径场积分法、平面波谱积分法等,它们大都是行之有效的,但要求对天线及天线罩进行一体化分析时,现有的经典方法往往不能迅速而准确地给出解答,如果用复射线理论这一新方法则可以对某些问题圆满地给出结果.根据复射线理论,利用复源点远场具有的高斯波束特性,无论是在远区或是近轴区域内,复源点场和高斯函数有很接近的相同分布,理论上论证了对于具有高斯波束分布的口径场可以用复源点场来近似模拟.     

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。     

Catia aided radome analysis using geometric optics method

In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements.     

纽扣式雷电分流条对雷达天线罩的传输影响分析

传统的金属雷电分流条难以满足高频雷达天线罩的电磁波传输要求,而纽扣式分流条可以兼顾防雷和电磁波传输。通过仿真和试验对比分析雷电分流条的电磁波传输特性,使分流条电磁波传输性能研究模型化。分析纽扣式分流条的电磁波传输机理,同时研究金属片形状、金属片间距和天线频率对雷达罩电磁波传输性能的影响。结果表明:金属分流条对雷达罩的电磁波传输性能影响严重,合理设计的纽扣式分流条可以有效传输电磁波;纽扣式分流条的金属片形状对电磁波传输影响明显,金属片横向越宽,对电磁波传输影响越大,圆形结构电磁波传输性能最差,窄菱形结构电磁波传输性能最好;纽扣式分流条的金属片间距对雷达罩的电磁波传输影响不大,主要影响其击穿电压;同一形式的纽扣式分流条,天线频率越高,电磁波传输性越差。     

应用PO-AI方法分析加罩OAM天线的辐射特性

应用物理光学-口面积分（PO-AI）方法,数值分析加载天线罩的轨道角动量（OAM）波天线的辐射特性,评判介质天线罩对各阶模式OAM波的辐射特性、幅相分布以及模式纯度的影响程度。通过与现有文献中天线罩实例的测试值相对比,验证了算法的正确性和有效性;考察了开口波导环形阵列OAM波天线工作于不同的模式阶数时,半球形天线罩所引起的空间场幅-相分布的变化。在此基础上,计算了一个正切卵形、多层介质天线罩情况,验证了PO-AI 算法对复杂结构的适应性。从数值结果可见,天线罩对高阶OAM辐射波的幅值分布影响较大。数值计算也证实该算法可以快速预估介质罩存在时OAM波形的畸变程度,有助于实现对天线罩各参数的快速优化。     

试验天线对雷达罩传输效率的影响及分析

在雷达罩电性能测试过程中,需要用到试验天线,试验天线的类型、极化方式和口径尺寸对雷达罩电性能测试结果有一定影响。文中对试验天线口径尺寸对雷达罩传输效率的影响程度进行了仿真计算,通过对比测试验证了仿真计算的正确性。计算和测试结果表明:当试验天线与装机天线口径尺寸差别不大时,试验天线口径尺寸对传输效率的影响较小。在工程实践中,当无法得到装机天线时,可以用类型相同、极化方式相同、口径相近的天线作为试验天线,以完成传输效率的测试。     

大型波导缝隙阵与天线罩的一体化高效精确分析

针对带罩大型波导缝隙阵的辐射特性分析, 基于并行区域分解合元极算法, 提出一种多区域的精确高效算法.将每根波导缝隙天线以及天线罩实体目标作为一个有限元计算区域, 各区域之间通过基于各区域表面的边界积分方程进行耦合, 并于天线罩内部应用区域分解技术来降低计算资源实现高效计算.与传统单区域合元极的数值结果比较验证了该多区域方法的精确高效性, 还计算分析了带罩大型波导缝隙阵的频域辐射特性.     

Complex ray analysis of beam transmission through two-dimensional radomes

Assessment of the radiation characteristics of certain types of radome covered antennas poses the problem of transmission of amplitude tapered large-aperture fields through a curved dielectric layer. Modeling the amplitude taper by a Gaussian, the incident illumination can be generated by a source at a complex coordinate location. The radome problem is then addressed by tracing complex ray fields from the complex source point through the complex extension of the radome configuration to the real location of the observer. No integrations over equivalent apertures are required here. The complex ray tracing has been performed for conventional complex geometric trajectories as well as more accurate trajectories with lateral shifts at the radome interfaces, and takes into account multiple reflections inside the radome. As previously for real rays, the multiple internally reflected complex rays can be combined into a "collective ray" that is weighted with a curvature and (or) taper corrected slab transmission coefficient. Numerical calculations for various two-dimensional circular cylindrical and wedge-tapered prototypes and various beam illuminations demonstrate the feasibility of the complex ray method, the efficiency of the collective ray concept, and the adequacy of the ray model without lateral shifts for the radome application.     

TM surface-wave power combining by a planar active-lens amplifier

Power combining of TM surface waves by a planar active-lens amplifier is the subject of this paper. An amplifier gain of 11 dB at 8.25 GHz with a 3-dB bandwidth of 0.65 GHz has been demonstrated. Gain is measured from input to output connector to facilitate comparisons with more conventional amplifiers. Measurements of output power versus input power are also presented. The amplifier behaved in a linear manner and no problems with spurious oscillations were encountered. Construction of the amplifier is compatible with planar fabrication technologies. A key component of the combiner is a microstrip-fed Yagi-Uda slot-array antenna for TM surface-wave excitation of a thick dielectric slab. Design and optimization guidelines for the antenna are presented as well as detailed spectral-domain and finite-difference time-domain (FDTD) analysis results. Measured and simulation results show an input return loss and front-to-back ratio better than 10 dB over a 5% bandwidth. Calculated and measured results for the fields radiated by the antenna confirm forward radiation of the dominant TM mode in the thick dielectric slab. Integration of the computed radiated fields shows the antenna has a surface-wave launching efficiency of 85%     

System performance in rain in a radome-enclosed environment

Computer modeling and analysis techniques have been established to evaluate performance during rain, in a radome-enclosed system. Electromagnetic transmission line theory using raytracing techniques is presented to compute transmission loss. Comparisons between theory and measured results are documented. Variations in water film thickness versus look angle and the resulting effect on performance are discussed. Other performance effects in rain, such as depolarization and noise temperature, are included in the analysis. The differences in performance using hydrophobic and non-hydrophobic materials can easily be predicted. Hydrophobic membrane materials are available for use with a radome, which yield excellent electromagnetic performance, even at mm wave frequencies. Recent tests are discussed which substantiate enhanced radome performance during rain.