Measurements of 20-GHz transmission through a radome in rain

An experiment has been designed to study the effects of rain on transmission through large radomes of the type which may be used with ground station antennas in satellite links. Measured transmission data from the experiment are described and compared with predicted values. The nonwetting nature of the radome surface significantly degraded with time, and this was accompanied by a large increase in the 20-GHz transmission loss during periods of rain. The losses were in the range of 6-8 dB for rain rates of 3-40 mm/h. The cumulative distribution of transmission through the radome for a 12-month period is presented.     

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     

Transmission Characteristics of Sandwiches (Correspondence)

The radome design equations which are in common use are based on the transmission characteristics of sandwiches. Transmission line techniques provide a convenient method for determining these characteristics. The transmission line analogy of wave propagation has been discussed by Ramo and Whinnery. A restricted application of this analogy is given in a report by Snow. In this note, a more general application will be discussed.     

Boresight errors induced by missile radomes

Radome induced boresight errors are defined in terms of antenna difference port to sum port voltage ratios. The antenna port voltages are derived using the reaction integral for the case of a planar waveguide slot array in the presence of a dielectric radome. Radome transmission uses planar slab results. Both the antenna reflection and the radome shadow contribution are taken into account. Although only linear copolarized comparisons are presented here, the analysis is kept arbitrary with respect to incident and seeker antenna polarizations. Measurements include a line source experiment that tests the antenna model sensitivity to geometry. A simple distributed source experiment, in the form of a planar slab radome with thickness corrugation, tests the influence of transmission through varying wall thickness. Effects of curvature are assessed with an offset hemisphere radome and finally a series of tangent ogive radome comparisons verify the limits of the analysis. A trend for the yaw errors to be less accurate than the pitch errors is consistently noted for the tangent ogive radomes, and this behavior is discussed.     

Radiation of an aperture antenna covered by a spherical-shellchiral radome and fed by a circular waveguide

This paper presents a full-wave analysis of the radiation characteristics of an aperture antenna that is flush-mounted on a ground plane and fed by a circular waveguide supporting the dominant TE₁₁ mode. The antenna is covered by a dielectric hemispherical chiral radome. Huygen's equivalence principle and the image theory are utilized to simplify the problem. The magnetic dyadic Green's function for the three-layered geometry is formulated and applied to analyze the radiated electromagnetic fields outside the chiral radome. Both the exact and approximate expressions of electric fields valid for the Fresnel and Fraunhofer zones are obtained using the spherical vector wave functions and their approximations in the far zone. Various chiral materials are assumed and computations of antenna parameters are carried out. The effects of the dielectric chiral radome on the radiation power patterns, sidelobe levels, and 3-dB beamwidths are also discussed numerically     

Rain Attenuation and Doppler Shift Compensation for Satellite Communications

In high‐speed multimedia satellite communication systems, it is essential to provide high‐quality, economical services by using efficient transmission schemes which can overcome channel impairments appearing in the satellite link. This paper introduces techniques to compensate for rain attenuation and the Doppler shift in the satellite communication link. An adaptive transmission technique with a control algorithm to adaptively allocate transmission schemes is used as a countermeasure to rain attenuation. We introduce a new rain attenuation modeling technique for estimating system performance and propose a novel Doppler shift compensation algorithm with reduced hardware complexity. Extensive simulation results show that the proposed algorithm can provide greatly enhanced performance compared to conventional algorithms. Simulation software and hardware which incorporate the proposed techniques are also demonstrated.     

用复射线理论研究波束经天线罩的传输

本文研究了三维复射线理论,给出了三维空间中一般的复射线追踪法,对旋转抛物形单层介质天线罩的波束传输特性进行了计算.根据计算出的数据绘制了远区和近区波束传输特性方向图,并与无介质天线罩时波束方向图进行了对比,从而明确了天线罩对波束传输的影响.     

磁性平板功率系数和插入相位移研究

该文采用电磁波反射、透射和传输线理论,建立了分析磁性平板功率传输系数和计算插入相位移的方法,给出了消除退极化现象天线罩材料电磁参数必须满足的数学公式。计算和分析了单层和典型A 夹层结构天线罩在电介质材料和磁性材料两种情况下表现出的传输特性,结果表明,磁介质平板材料电磁参数满足r = r (复介电常数等于复磁导率)时,可以避免退极化现象,功率传输系数优于对应的电介质平板,插入相位移变化更为平缓,表现出了最佳的传输特性。最后,利用商业软件HFSS 进一步验证了上述结论的正确性和该方法的有效性。      

单层圆柱磁性天线罩的电磁特性分析

利用复射线近轴近似法分析二维圆柱形磁性天线罩的电磁传输特性.分析了天线罩对罩内的雷达天线性能的影响.讨论了天线罩引起的传输系数和角跟踪性能的变化.数值结果表明,相对介电常数和相对磁导率相等的磁性天线罩具有最佳的电磁传输特性.     

Wet antenna effect on VSAT rain margin

The contribution of wet antennas to the antenna signal path losses in a VSAT environment is treated theoretically. The current commercial VSAT systems operating in either C-band or Ku-band generally have their remote terminal antenna reflectors and the antenna feed horn radomes coated with hydrophobic materials. The aim is to prevent the antenna and radome surfaces from becoming wet during a rainfall. This precaution relieves the burden of added rain margin necessary on the link budget. The magnitude of the propagation loss when the antenna reflector and the antenna feed horn radome surfaces are wet is determined. The results can indicate whether the expense of applying and maintaining the hydrophobic materials on the VSAT remote antennas and radomes is justified under specific loss conditions     

某型机载宽频带天线罩电气性能的测试研究

对2～18GHz的宽频带天线罩进行了测试研究,给出了天线罩电性能参数中的透波率和插入相位移的理论分析,并结合实际测量的数据进行了研究。测量结果表明,A夹层天线罩结构具有更好的透波性能,薄壁结构具有较均匀的插入相位移特性。在约束插入相位移的前提下,非对称夹层结构在透波性能、重量、抗弯刚度、抗弯强度方面更具优势。     

A streamlined metallic radome

The results of research and development, fabrication, and measured transmission performance for a specific streamlined metallic radome are contained in this paper. The measured results presented demonstrate that high-quality radome transmission performance can be attained with a streamlined metallic radome. The conical metallic radome presented is 6 ft 4 in long and has a base diameter of 25.5 in. The specially designed resonant slotted surface of the metallic radome consists of 90 percent metal and, for frequencies within its operating band, the radome permits transmission with any signal polarization over a wide range of scan angles. At its 8.90 GHz resonant frequency the metallic radome introduces less than 0.5 dB signal loss and less than 2 mrad boresight error. This radome has been purposely designed for operation over a narrow frequency band. Over a 200 MHz band, measured insertion loss and boresight error values of 1 dB and 6 mrad, respectively, are attained.     

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。     

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.     

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.     

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。     

Asymptotic approximations in radome analysis

A detailed analysis is presented of assumptions and limitations of physical optics and stationary phase techniques for radome analysis. A two-dimensional ogival structure with an electric or magnetic line source inside is investigated. A method-of-moments analysis using J.H. Richmond's (1965) polarization current technique is performed to obtain reference results. Physical optics, uniform geometrical theory of diffraction, and stationary phase techniques of order 1 and 2 are analyzed     

机载宽频带雷达罩双向变厚度设计方法

新一代战机的火控雷达向着宽频带和相控阵方向发展。针对宽频带相控阵机头雷达罩的高性能要求,提出了“高传输、低反射、等插入相位延迟”综合设计准则。分析了宽频带夹层罩壁结构的电性能特性,针对其相位特性差的情况给出了一种新的双向变厚度设计方法。通过雷达罩轴向变厚度设计以适配不同的入射角获得高传输/低反射性能,通过环向变厚度设计以适配不同的极化角获得接近的插入相位延迟,实现了优良的宽频带传输性能和方向图特性,在雷达罩产品研制中得到应用并发挥了重要作用。     

Electrical design of metal space frame radomes

Formulation and results are presented of a digital computer program, which analyzes the electrical effects of a metal space frame radome, using a single scattering approximation. Under the assumption of uniform or nearly uniform distribution of space frame elements over the surface of the radome, simple approximate formulas are presented for the same effects. Computed values agree well with measured data. The effects of shaping the element cross section, varying the radome geometry, and varying the frequency have been systematically studied in certain cases. The results are presented here as applications of the theory. The effects of multiple scattering have been measured and also analyzed by an approximate theory so that they are fairly well understood. Formulas for the effects of radome tolerances on electrical performance are given.     

雷达罩瞄准误差测量不确定度评定方法研究

雷达罩电性能测试系统是一种复杂的计量器具,需要对其检测结果的不确定度进行评定,以前在这方面几乎没有开展工作。以雷达罩电子定标法为例,对影响瞄准误差测试结果的主要因素进行了分析,确定了不确定度分量。采用A 类或B 类评定方法,对每个分量的标准不确定度进行了分析计算。研究了不确定度分量之间的相关性,并对合成标准不确定度和扩展不确定度进行了计算。该方法也可用于雷达罩传输效率、方向图畸变和功率反射等电性能参数测量不确定度的评定。