复杂目标电磁散射混合算法

分析了复杂目标高频散射雷达截面(RCS)计算理论,提出了一种有效的混合算法.改进了等效电磁流方法(IMEC),推导了几何光学/物理光学区域投影算法(GO/PO).IMEC能有效地消除反射边界和阴影边界的奇异性,GO/PO法用于计算多重散射.通过AutoCAD软件,使用三角面元法构建目标三维模型.目标的高频雷达散射截面通过几何光学、物理光学、改进的等效电磁流和几何光学/物理光学区域投影等混合方法计算获得.同时,计算了某型号导弹的RCS,理论值同测量结果基本一致,说明该方法能满足复杂目标电磁散射分析的需要.     

High-frequency RCS of complex radar targets in real-time

This paper presents a new and original approach for computing the high-frequency radar cross section (RCS) of complex radar targets in real time with a 3-D graphics workstation. The aircraft is modeled with I-DEAS solid modeling software using a parametric surface approach. High-frequency RCS is obtained through physical optics (PO), method of equivalent currents (MEC), physical theory of diffraction (PTD), and impedance boundary condition (IBC). This method is based on a new and original implementation of high-frequency techniques which the authors have called graphical electromagnetic computing (GRECO). A graphical processing approach of an image of the target at the workstation screen is used to identify the surfaces of the target visible from the radar viewpoint and obtain the unit normal at each point. High-frequency approximations to RCS prediction are then easily computed from the knowledge of the unit normal at the illuminated surfaces of the target. The image of the target at the workstation screen (to be processed by GRECO) can be potentially obtained in real time from the I-DEAS geometric model using the 3-D graphics hardware accelerator of the workstation. Therefore, CPU time for RCS prediction is spent only on the electromagnetic part of the computation, while the more time-consuming geometric model manipulations are left to the graphics hardware. This hybrid graphic-electromagnetic computing (GRECO) results in real-time RCS prediction for complex radar targets     

动态雷达目标RCS测量及分析

根据动态雷达目标RCS测量原理，结合RCS测量雷达外场试验，确定了动态测量方法、飞行航线、测量参数和数据处理方法，给出了对某飞行目标的实测结果，并与仿真结果进行了对比分析，为内场精确仿真动态飞行目标的RCS提供了依据。     

RCS of arbitrarily-shaped targets with the TLM method

The radar cross section (RCS) of several bodies proposed by the Electromagnetic Code Consortium (EMCC) is calculated using the transmission-line matrix (TLM) method with the symmetrical condensed node. The results are in good agreement with experimental and moments-method solutions when the TLM is used together with an appropriate boundary condition and a near- to far-zone transformation approach     

RCS of low observable targets with the TLM method

The transmission line modeling (TLM) method is applied to determine the radar cross section (RCS) of very thin conducting targets under critical illumination that are included in a benchmark of thin plates proposed by the Electromagnetic Code Consortium (EMCC) for validation of low-frequency electromagnetic computational codes     

多区域GRECO虚拟屏幕算法分析电大尺寸目标RCS

传统图形电磁计算(GRECO)方法所能计算的目标尺寸依赖于计算机屏幕的分辨率,因此无法计算电尺寸特别大的目标.为解决这一矛盾,采用了多区域方法,即通过将目标在屏幕上的成像分成多个部分分别显示以达到更细致地显示目标的要求.然而多区域方法无法识别各个区域结合部分的面元,因此提出了虚拟屏幕法,有效解决了这个问题.最后,通过数值算例验证了多区域GRECO虚拟屏幕法的有效性和准确性.     

涂覆吸波材料目标RCS测量校准试验研究

雷达吸波涂层易受涂覆工艺、物理特性和气动应力等因素影响而破坏飞机整体的隐身特性。为评估雷达吸波涂层状态,在紧缩场对涂覆雷达吸波材料的目标展开RCS测量和分析。雷达散射测量系统的测量精度受定标体几何参数精度、测量方法、校准方法、系统稳定性等多种因素影响。在金属球定标体几何参数、场地制造装配精度和安装定位精度等已溯源至国家基准的基础上,针对测量和校准需求,研究了替代置换法的测量校准原理,开展了测量和校准试验,结果表明：在扫频测量基础上,通过时域频域变换、背景矢量对消、时间窗等技术滤除杂波干扰而获取线性度较好的系统校准曲线,用于涂覆雷达吸波材料目标的RCS测量校准,能有效提高测量效率和精度,确保量值一致,满足隐身飞机雷达隐身状态监控和校准需求。     

VHF频段隐身目标缩比模型的雷达散射截面测量

介绍了甚高频（VHF）频段、工作在水平（H）或垂直（V）极化发射-接收组合（即HH、VV、HV、VH）情况下隐身目标缩比模型的雷达散射截面积（RCS）测量方法;给出了低频段RCS测量与计算的详细过程,采用背景杂波对消和时域加窗处理的方法减少了低频段RCS测量的误差;并给出了两种隐身目标缩比模型的RCS测量结果。测量结果表明：由于谐振效应,在VHF下端的低频段,隐身目标的RCS在平方米的量级,远大于在微波段的测量值;在部分频点,交叉极化的RCS甚至比同极化还强。这为利用隐身目标在频率域的谐振效应和极化域的极化特征,设计具有探测隐身目标能力的现代雷达提供了理论依据。     

A deterministic ray tube method for microcellular wave propagationprediction model

In this paper, we present a new and very fast ray-tracing method using a ray tube tree, which is based on uniform geometrical theory of diffraction (UTD) and can solve some of the problems that other ray-tracing methods have. It is developed for quasi three-dimensional (3-D) environments and can be applied to any complex propagation environment composed of arbitrary-shaped buildings and streets. It finds all propagation paths from a transmitter to a receiver extensively with very high computation efficiency. It is fundamentally a point-to-point tracing method, so reception tests are not required and it guarantees high accuracy. To validate our ray-tracing method, signal path loss and root mean square (rms) delay spread were computed in the downtown core of Ottawa, Canada, and they were also compared with the published measurements. The results of the proposed method in this paper show good agreement with the measurements. The computation time required to obtain a path loss map in the site is revealed to be very short in comparison with other methods     

基于改进物理光学法的电大目标双站RCS的预估

研究了电大尺寸目标双站电磁散射的改进物理光学法。针对以往双站高频算法由于忽略阴影区电流影响,导致大双站角下计算误差有所增大的问题,提取电流步进法中的迭代算子,考虑阴影区不同面元的耦合影响,与图形电磁计算方法相结合,推导出了改进的物理光学公式。分别提取照明区和阴影区面元,按照入射波方向进行排序迭代求解,快速有效地计算了电大目标的双站雷达散射截面(RCS)。通过与多层快速多极子,以及高低频混合方法进行对比,验证了该方法的有效性和准确性。     

基于杂波特征评估的雷达目标点迹过滤方法

雷达在目标检测和跟踪时常面临地杂波、海杂波、气象杂波等复杂强杂波的干扰,而雷达回波信号经过传统的动目标显示(MTI)和恒虚警(CFAR)检测处理后的剩余杂波,在距离-时间(脉冲)上的二维分布与目标非常相似,无法区分。对此,提出一种基于杂波综合特征评估的雷达目标点迹过滤方法,综合考虑目标与杂波在幅度起伏、距离/俯仰/方位相关性、相位变化等多维特征的不同,利用综合特征因子评估区分目标和杂波。最后,利用雷达实测数据对所提方法进行验证。结果表明,杂波有效抑制率较传统方法有显著提升。     

提高航管二次雷达近程目标跟踪稳定性的方法

针对相控阵体制航管二次雷达系统在雷达近程探测空域内无法稳定监视目标的问题,提出了一种提高航管二次雷达系统对近程目标跟踪稳定性的方法。基于现有航管二次雷达系统的硬件架构,设计了在对监视空域进行航管扫描询问过程中密集插入对近程目标跟踪询问的工作方式,并给出了航管近程跟踪询问流程和波位随机同步跳转控制时序的详细设计方法以及对航管近程跟踪能力的估算方法。仿真计算结果验证了该方法的可行性和有效性。     

A deterministic particle method for the kinetic model of semiconductors: The homogeneous field model

We present a new particle method for the simulation of the semiconductor Boltzmann equation—the weighted particle method. This method differs from the Monte-Carlo method by the approximation of the collision operator—we allocate each particle a weight which varies in time according to the collision integral. This integral is evaluated by means of a quadrature formula, which does not require the use of random numbers. The aim of this paper is to show that this method gives accurate results on physically relevant problems. Linear as well as non-linear collision integrals can be handled the same way by this method. Precise representations of the distribution functions are available, which allow a good insight into the physical processes. In this paper, we only consider the homogeneous field model with an emphasis on the collision operator. Numerical results are presented with a comparison with the Monte-Carlo method.     

一种计算复杂天线散射截面的新型快速方法

针对传统数值算法分析天线结构项单站雷达散射截面(Radar Cross Section,RCS)问题运算量大的缺点,基于压缩感知理论引入一种包含各个离散入射角度信息的新型激励源,借助有限元软件的建模分析功能,形成一种适用于处理复杂天线结构项单站RCS的快速算法.通过对单极子天线、角锥喇叭天线和抛物面反射天线等算例的仿真,验证了新算法处理复杂目标能力强、计算效率高的优势.     

A model based technique for recognizing targets by using millimeter wave radar signatures

A technique for recognizing real targets by millimeter wave (MMW) radar at 35 GHz and 94 GHz is presented. The recognition is performed by a model based technique in which real targets are represented by their high range resolution (HRR) profiles in hierarchical fashion. The unknown signal is classified by a model matching method and a coarse-fine searching technique. The advantages of this model based method are in low storage capacity, fast processing time and high recognition performance. Moreover this technique is very easily modifiable to incorporate multi sensor processing. We will present the results of the several experiments that we have conducted.     

自由空间复杂导体目标的太赫兹RCS高频分析方法

研究了自由空间复杂导体目标的太赫兹（THz）雷达散射截面（RCS）的高频求解方法。将并矢格林函数引入物理光学方法中,对自由空间环境进行考虑,推导出自由空间物理光学分析方法,并结合图形电磁计算（GRECO）方法,采用分区显示算法改进后,在Visual C++ 2010 程序中实现目标的OpenGL 显示,对自由空间复杂导体目标进行消隐判断,提取像素面元法矢量和深度缓存等有效信息,计算了自由空间复杂导体目标的THz RCS。最后,将程序计算结果与FEKO 软件仿真结果进行比较,结果证明该方法的有效性和准确性。该研究结果为THz 雷达未来在军事、天文和遥感等领域的应用提供了重要依据和方法。     

动态雷达目标RCS的统计分析

对于飞机等复杂目标,外场飞行动态测量是获取目标电磁散射特性数据的一个必要手段.基于动态飞行测量实验,详细分析了某中型民航飞机的外场实测RCS特性数据.研究了其统计特性,同时建立了该飞机在不同方位角范围内的起伏模型.研究结果可以为RCS的设计和减缩提供参考,并可应用于雷达目标仿真.     

用微分复倒谱方法实现雷达高分辨距离像对齐

根据雷达高分辨距离像具有非最小相位和小波特征的信号性质 ,采用 Z变换方法给出和研究了高分辨距离像的微分复倒谱的性质。提出用微分复倒谱方法实现雷达距离像幅度归一化和实现距离像方位对齐的原理及其算法。数值计算和实测雷达数据的计算机仿真结果表明 ,理论分析是正确的 ,提出的算法是可行的 ;该方法适用于雷达目标识别     

A characterization of subsurface radar targets

The capability of subsurface target identification at shallow depths has been demonstrated using an electromagnetic video or base-band pulse radar. Real radar measurements were collected for five targets at a depth of 5 cm (2 in) in various ground conditions. These measurements were processed for target characterization and identification. Identification performance based on a single radar observation was evalualted. The identification process requires only simple algebraic operations and thus offers the potential of real-time on-location identification of subsurface targets.