Research into Influence of Gaussian Beam on Terahertz Radar Cross Section of a Conducting Cylinder

In RCS measurement, usually the incident beam is a Gaussian beam or a similar beam source; however, in the theoretical RCS estimation, usually a plane wave is assumed as the incident beam for sake of simplicity. In this paper, the RCS of an infinite perfect conducting cylinder is estimated. In the estimation, the influence of a 2.52 THz laser beam on RCS is studied and the RCS in dependence with scattering angle and some other factors is obtained after the change of RCS equation; meanwhile, comparisons of RCS when the incident beam is a plane wave and a Gaussian beam respectively, are also given. The estimation results show, when the cylinder radius is 10 mm, choosing a beam width of 40 mm can keep the relative error less than 0.48 dB.     

高斯光圆柱太赫兹雷达散射截面的影响

通过对缩比模型的太赫兹波段雷达散射截面(RCS)测量,可以获得微波波段全尺寸目标的RCS值,因此,RCS估算和测量是当前太赫兹重要的应用技术之一。RCS估算中,通常假定入射光为均匀平面波,但在实际测量应用中,常常采用发射类似高斯光束的太赫兹源。进行了横电波情况高斯光束入射时,无限长理想导体圆柱的太赫兹雷达散射截面估算。仿真研究了2.52 THz激光准直入射和相位变化对后向雷达散射截面的影响,给出了RCS与散射角的变化曲线;同时与均匀平面波入射结果进行了比较分析。仿真结果表明,在测量圆柱半径10 mm且入射光距圆柱轴心距离1 m处的后向RCS时,用光斑半径30 mm的高斯光束较好。     

Influence of Gaussian Beam on Terahertz Radar Cross Section of a Conducting Sphere

In RCS estimation, usually a plane wave is assumed; while in real measurements at terahertz frequencies, generally a Gaussian beam or a similar beam source is adopted. In this paper, the RCS of a conducting sphere is discussed under the condition that the incident wave is a Gaussian beam. In the estimation, the influence of 2.52 THz collimated laser beam on RCS is discussed and the RCS changing with scattering angle and some other factors is obtained; at the same time, the comparisons between different incident beams, plane wave and Gaussian beam, are also given. The estimation results show that choosing a beam width of 40 mm is appropriate when the sphere radius is 10 mm and the distance between the sphere and the beam source is 1 m.     

太赫兹雷达散射截面测量研究进展

太赫兹雷达散射截面(RCS)测量技术是当前太赫兹重要的应用技术之一。利用太赫兹源,不仅可以测得目标太赫兹波段的RCS,还可以通过对缩比模型的RCS测量,获得微波波段全尺寸目标的RCS值。基于RCS定义及测量的一般要求,介绍了国外太赫兹RCS测量的主要成果;重点介绍三类测量装置及测量目标;给出部分代表性的测量结果。最后分析了利用飞秒激光器抽运晶体的太赫兹时域谱系统、CO2激光抽运太赫兹激光器的逆合成孔径雷达系统和信号合成器的相干探测系统在工作频率、待测目标尺寸和小型化等方面的特点。为我国太赫兹RCS测量技术的发展提供技术借鉴。     

箔条云极化特性与雷达散射截面测量研究

从最一般的电磁波椭圆极化方程出发,分析了线极化波和圆极化波的构成条件、极化分解和极化的合成方式;探讨了箔条云的散射特性和极化特性;重点研究了箔条云与测试雷达之间的极化特性匹配关系对散射截面测量结果的影响．最后,指出了箔条云雷达截面测量方式对箔条工程实践的作用．     

一种测量雷达截面积的方法

介绍了利用对比法对物体RCS进行测量的方法.其过程是采用已知雷达截面积的金属球作为标校物,通过对比获得被测物体的雷达截面积.     

特种车辆RCS减缩外形研究

从现代地面目标反雷达隐身的特点出发,确定了特种车辆主要的威胁区域,在比较多平面和融合式外形2种设计思想优缺点的基础上采用了多面体思想方面,对原车和隐身车建模,并用软件仿真了威胁区域内的RCS对比曲线,通过对比曲线分析了特种车辆RCS与外形的关系,在多面体外形设计方面总结了RCS缩减的经验和措施,为减小车辆雷达探测特征提供参考和改进依据。     

Multiply Reflected Gaussian Beams in a Circular Cross Section

A well-collimated beam reflected repeatedly within a circular cross section undergoes periodic focusing and defocusing. This behavior is of interest for tracking of beams around a type of acoustic surface wave disk delay line, and it also relates to beam monitoring after oblique injection into the endface of a multimode optical fiber. The problem is analyzed by considering first the field excited by an isotropic line source inside a dielectric cylinder, and then converting this to Gaussian beam excitation by assigning a complex value to the source coordinate location. Because the wavelength is small compared to the cylinder radius, ray-optical methods are employed to construct the solution, with inclusion of such novel ingredients as the lateral ray shift on a curved boundary. Results are obtained for the amplitude and phase of the ray and beam field and for such beam parameters as the location of the focus the minimum beam width and the rate of beam divergence between successive reflections.     

Radar Cross Section of General Three-Dimensional Scatterers

Two disparate approaches?the finite-difference time-domain (FD-TD) method and the method-of-moments (MOM) surface -patch technique-which permit highly realistic modeling of electromagnetic scattering problems are compared. New results of induced surface currents and radar cross section are presented for an important three-dimensional canonical cube scatterer. It is shown that a high level of agreement for the two modeling approaches is obtained for this scattering example.     

平板缝隙阵列天线的雷达截面积分析

本文用矩量法、物理光学法及消奇点技术,对大型平板缝隙阵列天线的散射进行了研究,计算了典型阵列的雷达截面积(RCS),并进行了实验验证,两者趋势基本一致。本文计算结果表明,平板对散射场的贡献(结构项)远大于缝隙对散射场的贡献(模式项)。     

雷达散射截面预估的可视化技术

ＲＣＳ计算的可视化技术是高频ＲＣＳ预估方法与计算机图形学相结合的方法，以非均匀有理Ｂ样条函数的构造自由曲面，以计算机硬件自动处理目标遮挡面，并自动提取计算所需的几何信息。本文给出ＰＯ方法和可视化方法结合的一些结果。     

外形隐身目标雷达散射截面高频散射特性的研究

外形隐身技术通过修改目标形状,可以在一定角域范围内显著减小雷达散射截面（Radar Cross Section,RCS）．对高频散射机理进行了综合分析,提供了简单形体外形隐身的理论依据,并在此基础上进行了案例计算,得出了外形隐身的结论。     

复杂目标双站图形电磁计算

应用物理光学法（ＰＯ）与等效电磁流法（ＥＣＭ）分别计算了复杂目标双站散射中面元与棱边的散射场。在ＷＩＮＤＯＷＳ ＮＴ／９８微机平台上利用软件图形标准接口Ｏｐｅｎ ＧＬ和硬件图形加速卡对目标和背景像素进行实时显示和自动消隐,通过对各像素点的散射场计算和要位综合求得总散射场,从而将ＧＲＥＣＯ扩展为双站图形电磁学。数学模型和实例说明了本方法的正确性,对＊＊战斗机双站ＲＣＳ进行计算,对将来虚拟现实系统环境     

短毫米波和太赫兹线性注真空器件研究

对短毫米波和太赫兹真空辐射源的发展现状进行了简要的综述,对高频结构的种类、器件类型、频率等进行了分析.文中重点介绍了W波段行波管、返波管的研究结果,以及利用MEMS技术加工高频结构的结果;还给出了220 GHz圆形电子注、带状电子注折叠波导慢波结构的设计和模拟结果;研究了带状电子注情况下耦合阻抗和轴向电场的平坦度,对于开展高频率器件实现高效率互作用打下了基础.     

Formation and Transport of a Dense Electron Beam with Near-Rectangular Cross Section

Problems of formation and transport of relativistic electron beams with straight axis and near-rectangular cross section keeping its initial orientation in the process of evolution are considered.     

激光雷达散射截面测量误差分析

论述了激光雷达散射截面(LRCS)信息的重要性,从基本定义出发,分析LRCS表达式及其物理意义。依据辐射传输原理和光电探测原理,推导LRCS测量数学模型。依据目标与照射光斑截面大小关系,引入了目标系数δ概念。从目标系数、辐射标定标准选择、激光照射系统性能、激光探测系统性能以及大气环境参数等诸多方面,较全面地分析了测量误差来源,以及减少或修正误差的方法,并以误差树的方式直观地表示了误差来源及影响作用。从测量数据可信性、可交换性和可用性原则出发,提出了测量数据记录要求,并编制了测量数据记录表。对开展激光雷达目标散射特性研究具有重要参考价值。     

A Method to Measure Radar Cross Section Parameters of Antennas

A new method to measure radar cross section (RCS) parameters of antennas is presented in this paper. This method relies on an equation derived for the received signal power which is represented as the superposition of structural-mode scattered, antenna-mode scattered, and leakage signals. The method also measures relative phase and provides the effect of the load connected to the antenna. The received signal power equation is solved using minimum mean square error estimation, and the solution is used to obtain structural-mode RCS, antenna-mode RCS, and relative phase of an antenna by applying short, open, and match load cases. A measurement example of RCS parameters of a microstrip patch antenna using a simple experimental setup is presented. The structural-mode RCS, antenna-mode RCS, and relative phase factor $cos(phi_{0})$ of the antenna, obtained using minimum mean square error estimation solution, are ${-}18.307$ dBsm, ${-}20.386$ dBsm, and 0.970, respectively. The present method requires less lengthy experimental measurements, while providing results that are more informative and accurate as obtained from previous methods.      

Conversion of Gyrotron Output into a Gaussian Beam Using the Far-Field

A compact system to convert gyrotron output into an intense gaussian beam has been designed by introducing an intermediate focusing element into the quasi-optical system. The design is significantly simplified by applying gaussian optics and confirmed by application of the Huygens equation. The beam quality is improved by truncating the sidelobes of the far-field. In spite of the beam truncation, only a small fraction (11 %) of the beam power is sacrificed.     

DRFM干扰对雷达的影响及对策研究

介绍了数字射频存储器（DRFM）技术在雷达对抗中的应用,描述了DRFM的结构和工作原理。由于目前还没有成熟的理论来对付DRFM干扰,重点研究了针对DRFM干扰采取的对策,为反DRFM干扰提供了重要的理论依据。     

采用FDTD法研究微带天线雷达散射截面的减缩

采用时域有限差分法(FDTD)方法以及新的含有内阻的磁流环激励同轴馈电模型研究了微带天线的辐射及散射特性,分析了集总负载加载和贴片表面开槽对微带天线雷达散射截面(RCS)的影响,研究了微带天线RCS减缩前后的回波损耗、增益及方向性的变化.研究表明,集总负载加载能降低谐振频率点的RCS,开槽方法能在天线辐射性能改变不大的情况下对微带天线的RCS具有较好的减缩作用.