基于快速多极子算法的飞机翼面RCS的计算

本文基于快速多极子算法对采用吸波结构的翼面进行计算,然后与全金属翼面的结果进行对比,验证吸波结构翼面在一定程度上能减小其RCS,实现更好的隐身性能。     

基于模式项散射的吸波结构

天线雷达散射截面(RCS)的缩减是隐身平台实现低散射特性的关键.吸波结构是缩减目标RCS的重要技术手段,而又难以避免对天线辐射性能产生恶化影响.针对微带天线提出了基于模式项散射的吸波结构设计方法,利用吸波结构模式项散射与微带天线的结构项散射进行对消,达到天线带外雷达散射截面缩减的效果.通过仿真验证,在工作中心频率为10...     

飞机尾翼吸波结构的优化设计

对二雏介质金属复合尾翼模型，当其外形和前缘介质结构电磁参数一定但介质和金属分界面夹角取不同值情况下，采用矩量法计算了在10GHzTM均匀平面波照射下该模型双站雷达散射截(RCS)，并作比较。结果表明在复合尾翼外形和前缘介质电磁参数一定情况下，当介质和金属V字形分界面夹角为90度时最利于减小后向雷达散射截面(RCS)。     

三维机翼前缘影区爬行波RCS研究

分析了三维机翼前缘影区的爬行波散射机理,建立了前缘影区爬行波的雷达散射截面(RCS)计算模型.根据光滑凸曲面的一致性绕射理论(UTD)给出爬行波的后向散射远区电磁场计算公式,按RCS定义计算爬行波散射贡献.采用微分几何原理分析任意凸曲面上的爬行波短程线特性,根据爬行波在光滑凸曲面上的短程线测地曲率为零的条件,给出一种三维机翼表面短程线计算方法.对三维机翼前缘爬行波进行计算和测试,并计算分析不同机翼参数对前缘影区爬行波的影响.计算结果和测试结果吻合良好,表明该方法计算爬行波RCS快捷有效,可应用于工程分析.     

不同吸波涂层对三维复杂目标的RCS影响的分析

利用有限元-快速多极子算法(FEM-FMM)分析了三维复杂目标涂有不同吸波涂层的雷达散射截面(RCS).以圆锥体为例,详细计算分析了涂敷有耗各向同性、正单轴各向异性、负单轴各向异性和纳米吸波材料4种典型吸波材料对目标电磁散射特性的影响,并首次讨论了每种吸波材料随不同涂层厚度对RCS的影响,得到了最佳隐身效果的吸波材料和涂层厚度的组合.结果表明,涂敷最佳吸波材料目标的后向RCS比目标没有吸波涂层时可以降低16.6dB.     

基于UC-EBG的吸波结构设计及其在微带天线中的应用

在共面紧凑型光子晶体结构(Uniplanar Compact Electromagnetic Bandgap,UC-EBG)基础上加载集总电阻,设计出一种新型吸波结构,并分析了其吸波原理。将其加载于微带天线,用于减缩天线带内雷达散射截面(Radar Cross Section,RCS)。仿真结果表明,在谐振频点,该吸波结构的吸波率达到99.8%。加载该结构后,天线的辐射性能基本保持不变,而对于垂直入射的TE波和TM波,其带内RCS分别减缩了26.22 dB和15.08 dB。实测结果与仿真结果较为吻合,证实了该结构可以减缩微带天线的带内RCS,从而提高其带内隐身性能。     

高超声速飞行器绕流流场电磁散射特性分析

采用七组元化学反应模型,数值模拟高超声速飞行器流场.基于流场结果,用分段线性电流密度递归卷积时域有限差分方法计算了P、L波段飞行器流场的后向雷达散射截面积(Radar Cross-Section,RCS)频率特性及双站散射特性,并分析了入射波频率和双站角对RCS的影响.结果表明:在计算频率范围内,等离子鞘套流场后向RCS基本上比飞行器本体后向RCS小,攻角对流场RCS有所影响,当入射波频率和等离子体特征频率相近时,等离子鞘套改善飞行器的隐身性能;入射波频率为1 GHz时,飞行器等离子鞘套流场和飞行器本体的双站RCS随双站角的变化交替变化,无明显规律.     

后勤通用厢式车反雷达隐身设计研究

从后勤通用厢式车反雷达隐身特点出发，分析了后勤通用厢式车受雷达探测威胁的主要区域，并确定了合理的雷达截面减缩量。在分析简单形体的雷达反射特性和与RCS相关的因素以及减缩RCS方法的基础上，详细分析了后勤通用厢式车的主要散射源，提出了从修改厢式车外形和采用雷达吸波复合材料及涂料两方面降低后勤通用厢式车雷达散射截面积的方法。     

一种超薄吸波材料及其在缝隙天线中的应用

该文设计了一种超薄雷达吸波超材料,从等效电路和表面电流、电场分布分析了其吸波机理,并将其应用于波导缝隙天线的带内雷达散射截面(Radar Cross Section, RCS)减缩。该吸波材料仅由两层金属及中间的有耗介质板组成,厚度约为/175,最大吸波率达99.9%,且具有入射角和极化稳定吸波特性。将该吸波材料加载到波导缝隙天线上,实验结果表明:加载后的天线,回波损耗和增益几乎不变,在21~21角域,天线带内RCS减缩均在3 dB以上,法线方向RCS减缩最大超过17 dB。     

一种加载超材料吸波体的新型三面角反射器设计

针对传统角反射器的性能强烈依赖于入射波长,难以对抗变频雷达探测的问题,设计了一种加载超材料吸波体的新型三面角反射器。在8 GHz与12 GHz两个频点,产生近似相同的后向雷达散射截面(RCS)。对该角反射器的性能进行测试验证。结果表明:加载超材料吸波体后,在12 GHz频点,其RCS值下降约3.6 dBsm,在8 GHz频点,其RCS值与普通角反射器相比,下降约0.1 dBsm。新型角反射器的性能满足设计要求,为有效对抗变频雷达对角反射器假目标的探测与识别提供了新的途径。     

折叠翼飞行器气动建模及变形稳定控制律设计

折叠翼飞行器是一个由机身和内外翼组成的多刚体系统,当机翼折叠时,展长、机翼面积、全机气动焦点和飞机重心都会随之改变.采用准定常假设,通过DATCOM计算了7组中间构型的气动参数,并通过Matlab曲线拟合工具对不确定的气动参数进行拟合.对折叠翼系统的仿射线性LPV模型进行了多胞形分解,并采用二次Lyapunov函数方法设计了鲁棒变增益状态反馈控制器.仿真结果表明在鲁棒变增益控制器的作用下,变体飞行器在机翼折叠过程中波动较小,且折叠结束后能够快速回到稳定状态.     

High-resolution radar imagery of the Mirage III aircraft

High-resolution radar imagery has attracted increasing interest in recent years. As more radars are endowed with a high-resolution capability, target classification will become a regular system function. In order to classify an aircraft using radar, one must have an understanding of how the radar imagery relates to the physical aircraft. This paper illustrates the more important radar backscattering features on a typical fighter aircraft. Radar backscatter from an aircraft can occur through a variety of mechanisms. Although direct specular and diffractive mechanisms usually account for the majority of the scattering, indirect phenomena such as cavity scattering and creeping wave scattering are significant. This investigation finds that scattering from engine cavities is a particularly important radar backscatter mechanism for a fighter aircraft. Radar data of an actual Mirage aircraft is collected from a target turntable facility. This data is processed to obtain high-resolution range profiles (HRRP) and inverse synthetic aperture radar (ISAR) images, which indicate the prominent radar scatterers on the aircraft. The imagery is qualitatively examined, and its suitability for target classification is discussed     

Ray analysis of a class of hybrid cylindrical aircraft wings

A new approach to the modelling of aircraft wings, based on the combination of hybrid quadric (parabolic and circular) cylinders, has been presented for electromagnetic applications. Closed-form expressions have been obtained for ray parameters required in the high-frequency mutual coupling computation of antenna pairs located arbitrarily on an aircraft wing     

Fly like a Bird

This paper discusses the development of a new aircraft based on a bird's flying principle. As currently envisioned, the ultra-slim vehicle would be unmanned, solar-powered, and made of strong, lightweight materials. Rather than a metal framework covered by riveted plates and hydraulically actuated parts, the plane's body and wings would consist of a plastic-like material called an ionic polymer-metal composite, which deforms when exposed to an electric field. If the voltages are applied just right, the material can be made to flap like a wing. On top of the composite wings would be paper-thin sheets of photovoltaic material and lithium-ion batteries, layered on by thin-film deposition. Energy efficiency is the largest benefit in this project. The solid-state aircraft would have many potential uses; gathering scientific data, relaying communications, and surveying terrain are but a few.     

Mitigation of wing flexure induced errors for airbornedirection-finding applications

Errors in array calibration are the dominant error source for direction finding (DF) in airborne platforms. This problem arises since wings in large surveillance aircraft exhibit significant flexure, and their actual instantaneous positions during array calibration and operational flight is likely to be quite different. Scattering from time-varying wing structures onto the belly mounted antennas therefore causes the array responses to deviate from the array calibration and gives rise to DF errors. We present a simple model for array manifold perturbations due to wing flexure that captures their effect. The model is physically motivated and has been validated using experiments on a scale-model aircraft in an anechoic chamber. Our model can be exploited to derive new versions of the classical DF estimation schemes including weighted subspace fitting (WSF)     

Aircraft measurements of the microwave scattering signature of the ocean

Microwave scattering signatures of the ocean have been measured over a range of surface wind speeds from 3 m/s to 23.6 m/s using the AAFE RADSCAT scatterometer in an aircraft. Normalized scattering coefficients are presented for vertical and horizontal polarizations as a function of incidence angle (nadir to55deg) and radar azimuth angle (0degto360deg) relative to surface wind direction. For a given radar polarization, incidence angle, and azimuth angle relative to the wind direction, these scattering data exhibit a power law dependence on surface wind speed. The relation of the scattering coefficient to azimuth angle obtained during aircraft circles (antenna conical scans) is anisotropic and suggests that microwave scatterometers can be used to infer both wind speed and direction. These results have been used for the design of the Seasat-A Satellite Scatterometer (SASS) to be flown in 1978 on this first NASA oceanographic satellite.     

飞行器部件低散射载体的分析与设计

降低弱散射源的雷达散射截面,增强飞行器部件的隐身性能至关重要。但部件脱离飞行器后,需依托载体才能得到准确的隐身性能。通过探究低散射载体设计机理和思路,考虑爬行波、行波、入射频率等影响因素,设计了一款低散射载体。通过理论建模、特征基函数法仿真计算和试验测试方法验证,所设计的低散射载体的雷达散射截面足够低,可有效消除弱散射源以外的其他杂波散射影响,还原部件真实状态,有利于提升弱散射源隐身性能评估的准确性,从而优化飞行器隐身设计。     

Multilevel fast multipole algorithm for electromagnetic scatteringby large complex objects

The fast multipole method (FMM) and multilevel fast multipole algorithm (MLFMA) are reviewed. The number of modes required, block-diagonal preconditioner, near singularity extraction, and the choice of initial guesses are discussed to apply the MLFMA to calculating electromagnetic scattering by large complex objects. Using these techniques, we can solve the problem of electromagnetic scattering by large complex three-dimensional (3-D) objects such as an aircraft (VFY218) on a small computer     

Roll-plane analysis of on-aircraft antennas

The roll-plane radiation patterns of on-aircraft antennas are analyzed using high-frequency solutions. This is a basic study of aircraft-antenna pattern performance in which the aircraft is modeled in its most basic form. The fuselage is assumed to be a perfectly conducting circular cylinder with the antennas mounted near the top or bottom. The wings are simulated by arbitrarily many-sided flat plates and the engines by circular cylinders. The patterns in each case are verified by measured results taken on simple models as well as scale models of actual aircraft.     

米波频段飞机目标全极化散射仿真与特性分析

该文基于全极化雷达对空探测和目标识别的应用需求,研究了飞机目标全极化散射特性,特别是交叉极化散射的产生原理和可利用性。在米波频段对隐身和非隐身飞机目标开展了数值建模和仿真计算;分析对比了不同飞机目标的极化散射空域分布特性,分析了不同的外形结构产生强交叉极化的条件。结果表明:非隐身飞机具有较丰富的极化散射特性,有利于雷达目标的极化识别。