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.

基于共享孔径技术的低RCS电磁超构表面天线设计

提出一种基于共享孔径技术设计低雷达散射截面(radar cross section,RCS)电磁超构表面天线的新方法.该方法首先设计具有低RCS性能的超构表面,然后借鉴共享孔径技术思想,将超构表面和传统天线的辐射结构直接共享口径紧密排列,得到新型低RCS天线结构,并结合电流分析和局部结构修正,优化天线的辐射性能,最终同时实现天线的良好辐射和宽带低RCS性能.为了阐明该方法,基于极化旋转机理设计了一款低RCS超构表面,采用共享孔径思想和电流分析,得到了一款宽带低RCS超构表面天线,详细分析了该天线的工作机理与性能.结果表明:设计的天线在保证较好辐射的同时,实现了超宽带RCS减缩,提出的设计方法摒弃了从天线到低RCS天线的传统设计思路,通过逆向思维,将散射的优化问题转化为辐射的优化问题,不仅实现了天线与超构表面的一体化设计,还显著地降低了低RCS天线优化设计的难度,加速了天线优化进程.

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.

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.

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。

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.

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.

Impact of emulsification of crude oil on normalized radar cross section

The emulsification of crude oil is caused by the oil flowing into the water,resulting in the increase of oil film tension,viscosity,water content,and volume,which brings great harm to the marine ecological environment and difficulties for the cleanup of marine emergency equipment.The realization observation of emulsification crude oil will increase the response speed of marine emergency response.Therefore,we set up crude oil emulsification samples to study the physical property in laboratory and conducted radar measurements at different incidence angles in outdoor.The radar is C band in resolution of 0.7 m by 0.7 m.A fully polarimetric scatterometer(HH,VV,and VH/HV)is mounted at 1.66 m(minimum altitude)height at an incidence angle between 35°and 60°.An asphalt content of less than 3%crude oil and the filtered seawater were used to the outdoor emulsification scattering experiment.The measurement results are as follows.The water content can be used to describe the process of emulsification and it is easy to measure.Wind speed,asphalt content,seawater temperature,and photo-oxidation affect the emulsifying process of crude oil,and affects the normalized radar cross section(NRCS)of oil film but wind is not the dominant factor.It is the first time to find that the emulsification of crude oil results in an increase of NRCS.

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.

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。

Analytical Estimation of Radar Cross Section of Infinitely Long Conducting Cylinder Coated with Metamaterial

Aerospace structures can be approximately modeled as a combination of canonical structures such as cylinder,cone and ellipsoid.Thus the RCS estimation of such canonical structures is of prime interest.Furthermore metamaterials possess peculiar electromagnetic properties which can be useful in modifying the RCS of structures.This paper is aimed at calculating the RCS of an infinitely long PEC circular cylinder coated with one or two layers of metamaterial.The incident and scattered fields of coated cylinder are expressed in terms of series summation of Bessel and Hankel functions.The unknown coefficients of summation are obtained by applying appropriate boundary conditions.The computations are carried out for both principal polarizations.The computed results are validated against the numerical-based method of moments.Further,the variation of RCS of the metamaterial coated PEC cylinder with material parameters,frequency,aspect angle and polarization is analyzed.

飞机动态RCS计算方法的修正与改进

飞机动态雷达散射截面(RCS)的分析能够为飞机隐身设计和测试评估提供重要理论支撑。针对现有动态RCS计算方法只能适用于有限角域的不足,对飞机本体系中雷达方位角的定义进行了修正,扩大了现有方法的适用范围。提出了一种新型的动态RCS计算方法,解决了现有方法中雷达视线角与飞机RCS值无法建立一一映射关系的问题,使用飞机本体坐标系与雷达照射坐标系的欧拉旋转角表征飞机的动态RCS值,相比传统方法具有更高的准确性。最后,仿真验证了当飞机处于机动状态时,新型的动态RCS计算方法得出的结果与现有方法相比有显著差异,其有效提高了动态RCS计算的准确性。

Radar Cross Section Calculation for Wing-Body Blended Targets

A new method of calculating the radai cross section (RCS) for wing-body blended targets is presented and verified. The method utilizes a computer program for modeling targets' geometry in terms of small pieces. The calculation is based on physical optics approximation. Examples are given to show the validity of the method.

用于量子微波接收机的原子气室探头RCS分析

基于里德堡原子的量子微波接收机具有超宽带、高灵敏度等显著优点,在雷达探测、信号侦察等电磁对抗领域具有巨大的应用潜力。经典的微波接收机采用金属天线作为传感器探头,而量子微波接收机的传感器探头是一个全介质的原子气室。文中对原子气室探头的雷达散射截面积(RCS)进行分析,通过将原子气室与经典的微带贴片天线进行仿真对比,展示了原子气室探头在2 GHz~18 GHz的宽频带内具有更低的RCS。此外,还对影响原子气室RCS的主要因素(结构、尺寸、相对介电常数等)进行仿真分析,给出了低RCS原子气室的参数选取基本原则。

MONOSTATIC RADAR CROSS SECTION FOR REFLECTOR ANTENNAS

The calculation formulas of monostatic radar cross-section (RCS) of arbitrary re-flectors with arbitrarily polarized plane-wave incidence are derived, where the spicular field isobtained by geometrical optics (GO) and the edge-diffracted field is calculated by the method ofequivalent currents (MEC). Some typical calculated results are given by means of RCS spatialgraphs. For both horizontal and vertical polarizations, the theoretical results obtained in thispaper agree very well with the experimental results as well as the results from uniform theory ofdiffraction.

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.

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.

THz time domain monostatic radar cross section measurement of metallic plates and dihedrons

THz Radar Cross Section(RCS)measurement setup based on THz Time Domain Spectroscopy(TDS)is built to provide large scaled targets test ability in recent years.As calibrations,the metal plates and dihedrons are used in our experiments.The measurements are performed in a monostatic terahertz time-domain setup.The author proposed time domain and frequency domain calibration methods for angular RCS of calibrations,comparing the measurements with the theory to verify the ability of the time domain measurement setup.

The Back-Scattering Cross Section of Radar Wave on Carbon Fiber

The radar back-scattering cross section of the carbonfiber is calculated in this paper.The carbon fiber’s crosssection is less than metal fiber’s.The carbon fiber canreduce the scattering of the magnetic wave.

CONTOUR DESIGN AND PRACTICE FOR A LOW RADAR CROSS SECTION VEHICLE

On the basis of the canard configuration a contour stealth design including chiefly the wing, the fuselage and their connection type is projected. The prime project of a blended wing body vehicle with canard is provided and through the change of the fuselage head form and the different fin disposals, the radar cross section (RCS) is optimized. The average value of RCS and the value of RCS in the ± 45 ° front sector for different designs are illustrated. The model measurement proves that the project having a sharp head fuselage and 30 ° angle double fin has the minimum value of RCS. The wind tunnel test to the model with RCS optimized proved that the vehicle project has excellent aerodynamic characteristics such as high lift curve slope, up to 26° stalling angle, high lift / drag ratio equal to 8, and also has low RCS value in the front sector and in the lateral sector.