一种基于解析积分的TDPO算法及其在散射问题中的应用

基于时域物理光学(Time-domain Physical Optics, TDPO)方法, 给出了三角面元剖分下散射场解析计算的求解思路.对三角面元进行二重积分求得散射场计算的最终表达式.与传统的TDPO方法相比, 在同等计算模型下, 解析方法具有更高的计算精度.在处理高频复杂问题时, 解析方法可以用更少的面元数量参与计算, 从而节省大量的计算时间与计算机内存.     

一维微粗糙面与其上方金属平板的复合电磁散射研究

研究了一维导体随机粗糙面与其上方金属平板的复合电磁散射。应用互易性原理使求解复合目标的二次散射场简化为求解包含平板上的极化电流和微粗糙面散射场的积分方程。利用物理光学近似和粗糙面微扰法分别计算了平板上的感应电流和粗糙面的电磁散射场,导出了复合散射模型单、双站散射的计算公式并给出了单站数值计算结果,讨论了后向复合散射截面随入射频率及平板尺寸、位置的变化关系。     

改进的物理光学法分析远场目标的电磁散射特性

提出一种改进的物理光学(PO)法来计算远场目标的电磁散射特性.这种方法通过严格的积分变换,经过详细推导,给出了目标单站RCS表达式,可以有效地处理任意外形的纯导体的雷达散射截面计算问题.通过Stokes变换,传统PO表达式中面积分转换为线积分,使得计算效率明显提高.通过一个金属圆形平板和一个金属三角板的算例演示,验证了新方法和PO的精度是相当的.最后,还展示了一个3维的例子.     

时域物理光学法分析均匀介质目标的瞬态散射

提出将时域物理光学法(TDPO)应用于计算电大均匀介质目标的时域散射场。将菲涅尔反射系数应用到频域物理光学近似中,由逆傅里叶变换推导出介质TDPO的表达式,从而使TDPO能够分析电大均匀介质目标的瞬态响应。同时给出了三角面片建模下入射波的遮挡消隐方法。计算了典型目标的瞬态散射响应和宽带雷达散射截面(RCS),与其他方法求得的结果吻合良好,验证了介质TDPO的正确性。     

基于时域物理光学法的涂覆目标瞬态散射分析

为了对涂覆雷达吸波材料(RAM)的电大尺寸目标的时域瞬态散射特性和宽带RCS进行快速计算,以满足工程上对目标电磁散射特性的计算向宽频带、向时域靠拢的需求。通过引入阻抗边界条件(IBC),计算了涂覆RAM 目标表面的等效反射系数,将等效反射系数代入频域物理光学法(PO)的表达式,并进行逆傅里叶变换(IFT),推导出了适用于涂覆RAM的目标的时域物理光学法(TDPO)积分表达式。使用OpenGL 控制图形处理器(GPU)来对目标的面元模型进行消隐处理,提高了运算速度。最后通过两个仿真算例,对TDPO与频域PO计算所得的时域瞬态响应和宽带RCS 进行对比,验证了TDPO计算结果与频域PO计算结果具有同等精度。     

任意形状线、面、体组成导体目标的电磁建模

本文用积分方程和矩量法分析具有任意线、面、体组成的理想导体目标的电磁散射和辐射特性.其中统一采用RWG基函数对线、面、体导体上的电流进行展开;对于任意的线-面,面-面连接情况,根据电流连续性条件,给出了通用的设置基函数和未知量的方法;对于辐射问题,给出了设置激励源与计算输入阻抗的方法.最后通过分析导体盒上的单极天线和宽带贴片天线验证了本文方法的可行性和有效性.     

相邻目标电磁散射特性的研究

本文研究了植被环境中相邻两目标的电磁散射问题.在互易原理的基础上,得到了计入相邻目标二次散射的散射场的积分表达式.推导得出了相邻有限长导体圆柱的二次散射场的闭式解,分析计算了其前向散射特性,并与矩量法的数值结果进行了比较.     

导体平板上铆钉的电磁散射分析

利用电场积分方程(EFIE)的矩量法分析了导体平板上有铆钉的电磁散射问题.铆钉和平板表面采用三角形面元进行剖分,面元上的电流分布用子域基函数表示,用伽略金法将电场方程转化为矩阵方程求解电流系数.数值计算了导体平板上有无铆钉时的雷达散射截面随入射角的变化,结果显示当平板上有多铆钉时,在一定的角度范围内,铆钉对雷达散射截面的影响非常明显并且与铆钉的分布情况有关.     

基于解析积分的TDSBR算法及其在目标散射中的应用

在传统的时域弹跳射线（Time Domain Shooting and Bouncing Rays,TDSBR）方法的基础上,采用基于解析积分的时域物理光学（Time Domain Physical Optics,TDPO）方法计算目标的散射场.与传统弹跳射线法相比,新方法明显减少了射线管的数量,节省了计算内存,是一种分析电大尺寸目标散射问题的高效方法.最后,通过数值计算结果验证了该方法的可靠性和高效性.     

NURBS曲面建模的电大目标的宽带RCS快速计算

该文采用物理光学方法(PO),快速计算了非均匀有理B样条 (NURBS) 曲面建模的电大目标的时域瞬态散射和宽带雷达截面(RCS)。通过对频域物理光学散射场表达式进行逆傅里叶变换推导出卷积形式的瞬态散射表达式;对频域物理光学积分进行逆傅里叶变换得到时域物理光学积分的表达式。为了避免数值积分的使用,将NURBS曲面等参数离散为一组三角面片,运用Radon变换得到了时域和频域物理光学积分的精确闭式表达式。遮挡消隐时使用改进的z-buffer方法进行了加速。对时域瞬态散射场快速傅里叶变换得到目标的宽带RCS。文中计算了高斯脉冲平面波入射下模型的瞬态散射响应和宽带RCS,数值结果表明该文方法具有很高的计算精度,且计算速度快于传统时域物理光学法(TDPO)。     

An efficient plane wave spectral analysis to predict the focalregion fields of parabolic reflector antennas for small and wide anglescanning

An efficient approach is described for calculating the field distribution in the focal region of an electrically large, symmetric or offset parabolic reflector antenna with an arbitrary rim contour, when the concave reflector surface is fully illuminated by an obliquely incident arbitrary electromagnetic plane wave. The dominant contribution to the focal-region fields is found by transforming the physical-optics integral over the reflector surface into a plane-wave spectral (PWS) integral. The PWS integral is evaluated rapidly via the fast Fourier transform (FET) algorithm to furnish, in only a single computation, the field for every place in the focal plane (or any plane parallel to it) within the focal region for a given direction of the incident wave. The correction to the physical-optics field is relatively small in the focal region and may therefore be neglected. Numerical results based on this PWS approach are presented, and their accuracy is established by comparison with results based on other approaches     

时域物理光学法计算目标的微波短脉冲散射

目标的短脉冲散射问题本质上是其宽带散射特性,从时域上获取短脉冲散射问题更为直接。时域物理光学方法具有计算速度快、物理近似意义清晰明确等特点,可直接计算电大尺寸目标的微波短脉冲散射的时域波形。介绍了时域物理光学的理论公式,通过三角型网格剖分建立目标模型,引入Radon 变换计算目标的“冲击响应”,利用卷积计算获得目标的微波短脉冲散射时域波形。通过仿真算例进行验证,计算双导体球模型散射回波验证了该方法的可行性;计算大飞机的微波短脉冲散射波形展示了该方法处理电大尺寸问题的能力。用该方法计算的目标短脉冲散射回波波形可直接作为信号处理研究的输入。     

Electric-dipole radiation over a wedge with imperfectly conductivefaces: a first-order physical-optics solution

We solve a three-dimensional (3-D) electromagnetic diffraction problem involving an obtuse wedge with penetrable planar faces and an electric dipole which is parallel to the edge of the wedge. The analytical formulation is based on Stratton-Chu (1941) integrals of the electromagnetic field, which is excited by the dipole source on infinitely extending planes that coincide with the faces of the wedge. Fictitious charges are introduced along the edge to account for the discontinuity of the electromagnetic field on the faces across the edge. We evaluate asymptotically the integral expressions for the electric-field intensity far from the edge to obtain uniformly valid formulas. Our first-order physical-optics solution incorporates single reflection from both faces, the lateral wave, the edge-diffracted space wave, the edge-diffracted lateral wave, and transition terms which ensure that the electromagnetic field is finite and continuous at the single-reflection and lateral-wave boundaries. The numerical results establish the validity of this solution through a reciprocity check and comparisons with other analytical solutions     

Improved method for computation of potentials in a realistic headshape model

The lead field analysis (LFA) algorithm, a new computational technique for the calculation of potentials on the surface of a realistic head shaped volume conductor model based on the boundary element method and the reciprocity theorem, is presented. The new algorithm, in comparison to the standard boundary element method, offers improved computational efficiency and lower storage requirements. It also yields more accurate surface potential results in the face of varying dipole source locations for a head shape boundary element model with a given number of nodes. Additionally, the algorithm results in quasi-analytic expressions of the derivatives of the surface potential with respect to the location of the sources, allowing the use of optimization techniques with better convergence properties. A set of simulations demonstrating the increased robustness of the LFA algorithm in the face of varying dipole source parameters is also described     

Near-to-far-field transformation by a time-domain spherical-multipole analysis

The contribution deals with a new time-domain near-to-far-field (NFF) transformation which is particularly suited for the finite-difference time-domain (FDTD) method. The far field is derived from the tangential field components on a surface enclosing the scatterer by employing a time-domain spherical-multipole representation. The necessary time-domain convolution is performed as "on the fly," in parallel with the FDTD time-stepping algorithm. The efficiency of the method is improved by incorporating a temporal linear interpolation of the near-field data. With the once obtained multipole amplitudes an analytic series representation of the time-domain far field is achieved, which allows a physical interpretability of the result. Moreover, this expansion serves as an ideal basis for a systematic and efficient post processing. The proposed technique may also be useful for other numerical and for asymptotic methods.     

A novel 3-D CPFDTD scheme for modeling grid nonconformally aligned transmitter structures

In this paper, a novel three-dimensional (3-D) subcell algorithm for modeling metallic objects which are nonconformally oriented within the finite-difference time-domain (FDTD) grid is proposed. The generally applicable algorithm is based on the contour-path (CP) technique and enables, in combination with an enhanced nonconformally aligned source model, a more accurate spatial representation of antenna structures than the common staircase approach. To evaluate the performance of the new algorithm, the simulation results are compared with the classical staircase approach for dipole antennas as well as for a generic phone. Significant improvements were achieved for all antenna parameters from the near and far field, i.e., feedpoint impedance, radiation pattern, and field distributions.