A Study on Multivariable Interactions Concerning Radar Cross Section Reduction through Geometric Attributes

This resolution 5 (25−1 factorial) study aimed to ascertain an understanding of the interactions between different geometries on the resulting Radar Cross Section (RCS) of a target. The results of the study are in line with the general understanding of the impact different geometries have on RCS but show that geometries can also influence the variance of measured RCS, and typical attributes that reduce RCS increase the variance of the measured RCS. Notably, an increased angle between the front face of a plate and the direction of the radar signal decreased RCS but increased the variance of the RCS measured.

Radar Cross Section Prediction and Reduction for Naval Ships

Radar cross section（RCS） is the measurement of the reflective strength of a target.Reducing the RCS of a naval ship enables its late detection,which is useful for capitalizing on elements of surprise and initiative.Thus,the RCS of a naval ship has become a very important design factor for achieving surprise,initiative,and survivability.Consequently,accurate RCS determination and RCS reduction are of extreme importance for a naval ship.The purpose of this paper is to provide an understanding of the theoretical background and engineering approach to deal with RCS prediction and reduction for naval ships.The importance of RCS,radar fundamentals,RCS basics,RCS prediction methods,and RCS reduction methods for naval ships is also discussed.

Wideband radar cross section reduction based on absorptive coding metasurface with compound stealth mechanism

A scheme of combing wave absorption and phase cancellation mechanisms for widening radar cross section(RCS)reduction band is proposed.An absorptive coding metasurface implementing this scheme is derived from traditional circuit analog absorber(CAA)composed of resistive ring elements which characterize dual resonances behavior.It is constructed by replacing some of the CAA elements by another kind of resistive ring elements which is singly resonant in between the original two resonant bands and has reflection phase opposite to that of the original elements at resonance.Hence the developed metasurface achieves an improved low-RCS band over which the lower and higher sub-bands are mainly contributed by wave absorption mainly while the middle sub-band is formed by joint effect of wave absorption and antiphase cancellation mechanisms.The polarization-independent wideband RCS reduction property of the metasurface is validated by full-wave simulation results of a preliminary and an advanced design examples which employ the same element configuration but different element layout schemes as partitioned distribution and random coding.The advanced design also exhibits broadband bistatic low-RCS property and keeps a stable specular RCS reduction performance with regard to incident elevation angle up to 35◦.The advanced design is fabricated and the experimental results of the sample agrees qualitatively well with their simulated counterparts.The measured figure of merit(i.e.,low-RCS bandwidth ratio versus electrical thickness)of the sample is 40.572,which is superior to or comparable with those for most of other existing metasurface with compound RCS reduction mechanism.The proposed compound metasurface technique also features simple structure,light weight,low cost and easy fabrication compared with other techniques.This makes it promising in applications such as radar stealth and electromagnetic compatibility.

Wideband radar cross-section reduction using plasma-based checkerboard metasurface

For stealth technology,in order to overcome the limitations of thin-layer plasma for electromagnetic waves attenuation and further broaden the radar cross-section(RCS)reduction(RCSR)band of the metasurface,the plasma-based checkerboard metasurface composed of plasma and checkerboard metasurface is investigated to achieve better RCSR.We designed a checkerboard metasurface which can achieve abnormal reflection to reduce RCS and whose-10d B RCSR bandwidth is from 8.1 to 14.5 GHz,the RCSR principle of it lies in the backscattering cancellation,which depends on the phase difference of artificial magnetic conductor(AMC)units.The designed plasma-based checkerboard metasurface is a thin composite structure,including a checkerboard metasurface,a plasma layer,and an air gap which is between them.Full wave simulations confirm that the plasma-based checkerboard metasurface’s–10 dB RCS reduction bandwidth and RCS reduction amplitude,are both increased under different polarized waves compared with the only single plasma or the only metasurface.We also introduced the reason and mechanism of the interaction between plasma and the checkerboard metasurface to improve the RCSR effect in detail.As plasma-based checkerboard metasurface does not need the plasma to be too thick for plasma stealth,its application in practical scenarios is easier to implement.

Recognition of the major scattering sources on complex targets based on the high frequency radar cross section integrated calculation technique

Based on the high frequency （HF） integrated radar cross section （RCS） calculation approach, a technique of detecting major scattering source is developed by using an appropriate arithmetic for scattering distribution and scattering source detection. For the perfect adaptability to targets and the HF of the HF integrated RCS calculation platform, this technique is suitable to solve large complex targets and has lower requirement to the target modeling. A comparison with the result of 2-D radar imaging confirms the accuracy and reliability of this technique in recognition of the major scattering source on complex targets. This technique provides the foundation for rapid integrated evaluation of the scattering performance and 3-D scattering model reconstruction of large complex targets.

RCS Reduction of Airborne Dispenser

The radar cross section (RCS) of dispenser and its components is computed by graphical electromagnetic computing (GRECO) method, which bases on physical optics (PO) method. A satisfied agreement is gotten between computed and measured results outdoor. The results show that the main scattering source of the dispenser is the mirror reflecting of the body; in the most crucial nose-on region, the nose mirror reflecting plays important role; the corner reflecting is important to the fins' RCS. The corresponding measures to reduce dispenser's RCS are proposed. It is indicated that to reduce RCS, shaping should be adopts first, while aerodynamic characteristics and stealth characteristics should be considered synthetically during the design of dispenser.

Design of Tapered Novel AMC Chessboard Reflector for Broadband RCS Reduction

An artificial magnetic conductor(AMC)chessboard reflector is designed which shows low backscattered radar cross sections(RCS)in a broad frequency band in this paper.Designed by the phase cancellation principle,a conventional chessboard low RCS metasurface can be formed by polarization-dependent mushroom-shaped AMCs.Two new features are added to this design based on the conventional chessboard metasurface.Firstly,the long edge of the metallic patch on the AMC element is concave to obtain a broader bandwidth.Then,the width of the patch in each AMC block is tapered in one direction to further extend the operating bandwidth for RCS reduction.The backscattered RCS of the tapered AMC reflector is numerically investigated and compared with a non-tapered one.It is found that by introducing the above features,an RCS reduction greater than 10.dB can be obtained by the reflectors with relative bandwidth of 46%in the X-band.

Ship Appearance Optimal Design on RCS Reduction Using Response Surface Method and Genetic Algorithms

Radar cross section (RCS) reduction technologies are very important in survivability of the military naval vessels. Ship appearance shaping as an effective countermeasure of RCS reduction redirects the scattered energy from one angular region of interest in space to another region of little interest. To decrease the scattering electromagnetic signals from ship scientifically, optimization methods should be introduced in shaping design. Based on the assumption of the characteristic section design method, mathematical formulations for optimal shaping design were established. Because of the computation-intensive analysis and singularity in shaping optimization, the response surface method (RSM) combined genetic algorithm (GA) was proposed. The poly-nomial response surface method was adopted in model approximation. Then genetic algorithms were employed to solve the surrogate optimization problem. By comparison RCS of the conventional and the optimal design, the superiority and effectiveness of proposed design methodology were verified.

局部外形参数对高速飞行器的RCS影响

为了降低高速飞行器的雷达散射截面(radar cross section,RCS),采用多层快速多极子算法和物理光学法研究局部外形参数对飞行器雷达散射特性的影响。在此基础上,提出一种变半径弧形的边缘钝化形式,以提高飞行器仰视对抗能力。所提出的变半径弧形钝化外形具有良好的RCS减缩能力,与传统圆弧钝化外形相比,在前向重点角域内,RCS对数均值降低了22.88%;随着仰角的增大,变半径弧形钝化形式还具备全向RCS减缩能力,在全向角域内RCS对数均值降低了13.37%。最后,研究所提出的变半径弧形钝化方式在不同雷达波频段下的RCS特性,结果表明这种钝化方式对于频率较高时仰视对抗能力更好。

吸波材料覆盖直升机强散射源RCS缩减分析

针对武装直升机的宽带隐身问题,提出利用射线追踪和逆合成孔径雷达(Inverse synthetic aperture radar,ISAR)成像确定直升机强散射源位置的方法,形成电磁超构材料和磁性材料一体化设计直升机部分强散射源的隐身设计构想,并计算分析了两款隐身材料加载后对整机隐身效果的影响。首先,分析等效媒质理论、射线追踪与ISAR成像原理。然后,通过射线追踪以及ISAR成像的计算,精确且直观地捕获强散射源部位。最后,给出了两款材料的反射系数并分析加载直升机后单站雷达散射截面(Radar cross section,RCS)变化。计算结果表明,两种不同类型隐身材料覆盖直升机强散射源部位后可以达到局部角域范围内RCS缩减的目的,为隐身材料和直升机蒙皮及旋翼的融合设计提供了参考。

直升机尾桨参数对RCS影响分析

在执行战时任务时,对武装直升机的隐身性能提出了较高要求,为降低直升机在执行任务时被发现的概率,基于几何光学法和一致性绕射理论,研究直升机尾桨翼型厚度、弯度、剪刀角角度对RCS的影响。选用两种雷达照射方位,通过对尾桨不同参数和涂敷吸波材料的RCS峰值、均值对比,判断更有利于直升机尾桨隐身的条件。结果表明:雷达从地面照射时,尾桨厚度小、弯度小的RCS会适当减小,剪刀角角度的变化会导致RCS峰值相位变化;雷达平行照射时,厚度小的尾桨RCS小,弯度小的RCS峰值更小;在桨叶前缘与桨尖端面涂敷吸波材料可以有效降低桨叶整体RCS。因此,选择尾桨的厚度越小、弯度越小,有利于降低直升机尾桨的RCS,对桨尖端面和桨叶前缘进行吸波材料涂敷可以有效降低整体RCS。

Solution for polarimetric radar cross section measurement and calibration

The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algo-rithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix （RPCM） with a simpler expression is presented for the monostatic radar polarization scattering matrix （PSM） measurement. Using a rhombic dihedral corner reflector and a metal ic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metal ic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.

Radar Cross Section Analysis Using Physical Optics and Its Applications to Marine Targets

Radar Cross Section (RCS) is one of the most considerable parameters for ship stealth design. As modern ships are larger than their predecessors, RCS must be managed at each design stage for its reduction. For predicting RCS of ship, Radar Cross Section Analysis Program (RACSAN) based on Kirchhoff approximation in high frequency range has been developed. This program can present RCS including multi-bounce effect in exterior and interior structure by combination of geometric optics (GO) and physical optics (PO) methods, coating effect by using Fresnel reflection coefficient, and response time pattern for detected target. In this paper, RCS calculations of ship model with above effects are simulated by using this developed program and RCS results are discussed.

Ultra-wideband low radar cross-section metasurface and its application on waveguide slot antenna array

A novel approach devoted to achieving ultra-wideband radar cross section reduction（RCSR） of a waveguide slot antenna array（WGSAA） while maintaining its radiation performance is proposed. Three kinds of artificial magnetic conductors（AMCs） tiles consisting of three types of basic units resonant at different frequencies are designed and arranged in a novel quadruple-triangle-type configuration to create a composite planar metasurface. The proposed metasurface is characterized by low radar feature over an ultra-wideband based on the principle of phase cancellation. Both simulated and measured results demonstrate that after the composite metasurface is used to cover part of the antenna array, an ultrawideband RCSR involving in-band and out-of-band is achieved for co-and cross-polarized incident waves based on energy cancellation, while the radiation performance is well retained. The proposed method is simple, low-cost, and easy-tofabricate, providing a new method for ultra-wideband RCSR of an antenna array. Moreover, the method proposed in this paper can easily be applied to other antenna architectures.

基于DTCWT-VAE的弹道中段目标RCS识别

针对弹道目标雷达信号易受环境影响、目标识别准确率低的问题,提出了一种基于双树复小波变换(dual-tree complex wavelet transform,DTCWT)和变分自编码器(variational autoencoder,VAE)的弹道目标雷达散射截面(radar cross section,RCS)识别法。首先,采用DTCWT对弹道目标RCS动态数据进行预处理,再利用VAE提取目标的隐变量特征,最后用支持向量机(support vector machine,SVM)分类器进行识别。实验结果表明,与已有方法相比,该方法具有更高的识别概率,且鲁棒性较好。

Radar cross section of arbitrary polished spheres at terahertz frequencies

We develop an efficient method for polished metallic sphere’s scattering prediction in terahertz band when its frequency dispersion property is considered. By deducing scattering solution of the lossy metallic sphere, the radar cross section(RCS)of different metallic spheres is given at terahertz frequencies. The investigation of the RCS of polished metallic spheres shows the normalized RCS is always same to the metals’ normal incidence reflectivity when the sphere becomes electrically large. The metals which have high reflectivity(such as Al, Cu, Ag and Au) show that the corresponding RCS of the spheres is almost πa2 in terahertz band. The sphere’s RCS of the transition metal such as Fe begins to decrease obviously since the far infrared.

超电大复杂目标RCS缩比模型预估方法

本文提出用缩比模型计算超电大目标雷达散射截面 (RCS)的理论。通过对复杂目标近远场电磁散射理论模型的分析得到 ,目标的雷达截面和目标的几何尺寸及工作波长有关系。当电尺寸相同时 ,目标雷达散射截面和其几何尺寸的平方成正比。缩比模型计算既适用于近场 ,也适用于远场。

RCS测试中的低散射载体设计及仿真分析

在雷达散射截面(RCS)测试中,低散射载体的设计结果取决于被测目标的RCS量级;为进行细节性隐身设计,获得台阶与缝隙排除载体干扰后的RCS水平,提出一种在台阶与缝隙RCS测试中的低散射载体设计方法;采用多层快速多极子算法,对低散射载体相邻曲面连接方式、台阶与缝隙在载体上的位置、前缘尖削度、倒圆半径对散射特性的影响进行仿真分析;仿真计算结果表明,控制载体表面曲率的变化、加大前缘尖削度、减小拼接曲面倒圆半径能有效降低载体前向散射水平,由于载体曲面一侧的散射水平低于平面一侧散射水平,台阶与缝隙特征应位于曲面上;对RCS测试中低散射载体设计具有指导意义。

通用直升机雷达散射特性及RCS减缩

采用物理光学法和等效电磁流法作为RCS(Radar Cross Section)数值计算方法,通过对某飞机模型的实验测试,验证了算法的有效性.建立了某通用直升机的几何外形模型,计算RCS特性并分析其重要散射源.进行机身外形和旋翼的RCS减缩研究,提出了通用直升机隐身外形设计方法.改形后全机雷达散射水平在头(尾)向和侧向分别降低至原型的10%和1%,且静稳定性及有效容积基本不变.通用直升机进行外形隐身设计后,旋翼成为全机的重要散射源(特别在头向及尾向),还须采用其他方法进行RCS减缩.

姿态扰动情况下的目标动态RCS分布特性

运动目标姿态扰动是静动态雷达散射截面(radar cross section,RCS)差异的主要来源。造成姿态扰动的因素复杂且不可预估,增加了动态RCS分布特性研究的难度。将图形电磁计算与蒙特卡罗仿真结合,构建以均匀随机分布为扰动模型的动态RCS仿真分析平台。根据静动态RCS差异的统计分布特性,提出置信区间以及数学期望值的计算方法。选择两种运动模式下的飞机目标进行验证,将所得结果与实际扰动模型的动态RCS进行了比对。结论表明该方法具备较强可操作性和工程应用价值,提高了计算机动态RCS仿真能力,为目标静动态电磁散射特性一致性评估以及特征库构建提供了有价值的参考信息和分析方法。