一种计算多面体目标RCS的等效边缘电磁流公式

本文将Ａｏｄｏ计算平面目标物理光学（ＰＯ）场的等效边缘电磁流（ＰＯＥＥＣ）公式推广到能够计算复杂多面体目标的ＰＯ场，并对之修正，使该公式仅存在一个奇异点。这种ＰＯＥＥＣ和具有很少奇异点仅能计算边缘绕射场的等效边缘电流（ＰＴＤＥＥＣ）之和得到了能够计算散射总场且具有良好属性的ＧＴＤＥＥＣ。用导出的ＧＴＤＥＥＣ公式计算正方体和圆柱的双站ＲＣＳ，计算结果与实验和其它方法的结果吻合得到相当好，证实了ＧＴＤ     

等效电磁流一般和高阶表达式及其在双站散射中的应用

本文根据等效电磁流方法的概念，导出了求解物理光学场，边缘绕射场和总场的等效电磁流的一般表达式，它们可退化到目前已存在的各种等效电磁流公式；并提出了一种最佳的计算物理光学场的等效电磁流公式，根据半平面非均匀性电流的精确表达式，导出了一阶，二阶和三阶等效边缘电磁流的表达式，最后用本文导出的公式计算了菱形板的双站散射截面，计算结果和实验结果吻合良好。     

修正劈表示的边缘等效电磁流的改进及在电磁散射中的应用

本文介绍了修正劈的概念和用其表示的等效边缘电磁流（ＥＥＣ）公式，并应用它们计算了圆盘双站雷达散射截面（ＲＣＳ）；提出一种确定修正劈方向的法则，这种法则是根据几何绕射理论（ＧＴＤ）中有关参数的定义确定的，因而它不是经验的法则。修正劈表示的ＥＥＣ仅利用了经典的Ｋｅｌｌｅｒ锥上的绕射系数公式和修正劈的概念就可得到任意入射和观察方向的ＥＥＣ，它克服一般ＥＥＣ在Ｋｅｌｌｅｒ锥外的方向上定义模糊的缺点。数值结     

涂覆吸波材料飞行器机翼的RCS计算

本文首先研究了半平面阻抗劈在平面波斜入射下的广义Ｍａｌｉｕｚｈｉｎｅｔｓ电磁散射解，然后把应用于理想导体劈的等效边缘电磁流（ＥＥＣ）概念推广应用到涂覆吸波材料的阻抗劈上，由阻抗劈等边缘电磁流，计算了涂覆吸波材料的机翼的雷达散射截面（ＲＣＳ），并对所得结果进行了比较和验证。本方法特别适合大电尺寸目标的ＲＣＳ计算。     

缝隙天线阵双站电磁散射的混合法

利用矩量法（ＭＯＭ）和等效边缘电磁流方法（ＥＥＣｓ）研究波导馈电的缝隙天线阵的双站散射问题。从理论和计算上分析,等效边缘电磁流方法可以计算有限尺寸的导体平板沿任意方向上的双站散射（包括边缘绕射场）,而矩量法可以考虑波导缝隙天线阵的散射与耦合问题,使它们混合便可以解决有限尺寸缝隙在线阵的散射问题。实际计算表明,方法是切实可行的。     

阻抗劈中的等效边缘电磁流

本文把应用于理想导体劈中的等效边缘电磁流概念推广应用到阻抗劈上，导出了劈边缘在产面波斜入射情况下与阻抗劈绕射密切相关的等效边缘电磁流表达式，然后利用辐射积分公式，给出了有限长直劈的电磁散射解。为计算平板模型机翼的ＲＣＳ打下了理论基础，文中给出的计算实例说明了本文方法的有效性。     

图形电磁计算法分析高频区复杂目标虚拟双站散射特性

通过应用单－双站等效原理，将目前分析高频区复杂目标后向ＲＣＳ最有效方法之一的图形电磁计算（ＧＲＥＣＯ）技术拓广到计算双站ＲＣＳ领域，并给出了与实验结果符合良好的标准体与复杂目标的虚拟现实实例的单双站ＲＣＳ计算曲线，具有很好的工程应用价值。     

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     

快速计算电大尺寸目标双站电磁散射的方法

提出利用等效边缘电磁流方法快速计算复杂形体电大尺寸目标的双站ＲＣＳ。该方法运算速度快,考虑了边缘绕射和遮挡,计算精度高。在计算尖锥柱等典型散射体的ＲＣＳ的基础上,计算了一导弹模型在不同方位角下的双站ＲＣＳ,证实了本方法的可行性。     

一致性等效边缘电磁流的经验公式

本文给出了一种改进的等效电磁流公式，该公式是基于Ａ．Ｍｉｃｈｅａｌｉ的表达式的。当观察方向位于Ｋｅｌｌｅｒ锥上时，改进的Ｄｅ，Ｄｍ表达式可化简为Ｋｏｕｙｏｕｍｊｉａｎ的绕射系数，等效电磁流的表达式同Ｋｎｏｔｔ和Ｓｅｎｉｏｒ的表达式完全一样。在阴影和反射边界上，改进的等效电磁流公式具有一致性。     

Equivalent edge currents for arbitrary aspects of observation

Explicit expressions for equivalent edge currents are derived for an arbitrary local wedge angle and arbitrary directions of illumination and observation. Thereby the method of equivalent currents (MEC) is completed as a practically applicable theory of the electromagnetic high-frequency diffraction by edges. The derivation is based on an asymptotic relationship between the surface radiation integral of the physical theory of diffraction (PTD) and the line radiation integral of MEC, and the resulting expressions are deduced from the exact solutions of the canonical wedge problem.     

Elimination of infinities in equivalent edge currents, Part II: Physical optics components

A solution finite for all directions of illumination and observation is derived for the physical optics (PO) components of equivalent edge currents. The solution is based on the uniform asymptotic theory of endpoint evaluation of integrals. An extension taking into account the variation of the surface metric with the distance from the edge is presented, and a similar extension for including slope diffraction is indicated. The expressions derived complement the results of our previous work on elimination of infinities from the fringe components of equivalent currents.     

Uniform physical theory of diffraction equivalent edge currents fortruncated wedge strips

New uniform closed-form expressions for physical theory of diffraction equivalent edge currents are derived for truncated incremental wedge strips. In contrast to previously reported expressions, the new expressions are well behaved for all directions of incidence and observation and take a finite value for zero strip length. This means that the expressions are well suited for implementation in general computer codes. The new expressions are expressed as the difference between two terms. The first term is obtained by integrating the exact fringe wave current on a wedge along an untruncated incremental strip extending from the leading edge of the structure under consideration. The second term is calculated from an integration of the asymptotic fringe wave (FW) current along another untruncated incremental strip extending from the trailing edge of the structure. The new expressions are tested numerically on a triangular cylinder and the results are compared with those obtained using the method of moments and the previously reported expressions     

Reflector antenna radiation pattern analysis by equivalent edge currents

Equivalent edge currents, derived from the edge diffraction theory for a half-plane, are used to obtain the radiation patterns of a parabeloidal reflector antenna when illuminated by a source at the focus. Cylindrical wave diffraction coefficients are used. The method avoids infinities at caustics and shadow boundaries thus giving solutions which are finite everywhere. A slope-wave equivalent current correction term is applied when the illumination is tapered towards the edge of the reflector. Comparisons are given with the physical optics approach and experimental results.     

PTD analysis of impedance structures

Based on an approximate dyadic diffraction coefficient, equivalent currents (ECs) are derived for computing the scattering by a finite-length impedance wedge of arbitrary angle. The derived equivalent currents are implemented in a standard general purpose physical theory of diffraction (PTD) code and results are presented demonstrating the accuracy of the formulation for a number of impedance and (dielectrically) coated structures. These include typical shapes such as plates, finite-length cones, and cylinders which have been partially or fully coated. The PTD implementation requires a dyadic physical optics diffraction coefficient which is presented in the appendix     

一种新的等效电磁流边缘分量表达式

增量长度绕射系数是目前用于计算边缘绕射场的一种方法,但对给定的入射波方向,在某此观察方向上,该方法会呈现出某些奇性.为消除上述奇异性,Michaeli推出了等效电磁流边缘分量的另外一种表达式,该表达式除存在Ufimtsev奇点外在所有观察方向上均不发生奇异.然而Michaeli的表达式不是增量长度绕射系数的推广,在增量长度绕射系数不奇异的情况下,两者的计算结果可能会有较大的差别.本文提出了一种新的等效电磁流边缘分量表达式.与Michaeli的同类表达式相比,新表达式既能有效克服增量长度绕射系数(ILDC)方法中的某些奇异性困难,又能与ILDC保持很好的一致性,因此更具实际应用价值.     

GRECO中棱边检测方法及其绕射场计算的改进

图形电磁计算(GRECO)方法是计算复杂目标高频区雷达散射截面(RCS)的有效方法之一.本文分析了原始GRECO方法在判定目标图象棱边象素的不足之处,给出了相应的改进措施.改进后的软件能够更准确、充分地判定目标的棱边象素及获得棱边参数.在边缘绕射场的计算方面,本文指出了相关文献中存在的错误^[1],给出了基于等效电磁流法(MEC)和物理绕射理论(PTD)的边缘绕射场计算式,及与物理光学(PO)场叠加求取RCS的完整表达式.计算实例表明,新的方法具有更高的准确度,与实验测量值吻合.     

Closed-form expressions for uniform currents on a wedge illuminatedby TM plane wave

Closed-form expressions for nonuniform currents on a perfectly conducting, infinite wedge illuminated by a transverse magnetic plane wave are presented. The expressions are derived by requiring that they agree with the current predicted by the eigenfunction solution close to the edge and J.B. Keller's geometrical theory of diffraction (1962) far from the edge. The angle of incidence is arbitrary and the expressions remain uniformly valid even for glancing angles of incidence when the geometrical optics boundaries are in the vicinity of the wedge faces. The formulas presented are simple, involving Fresnel functions with complex arguments. These functions can be expressed in terms of complimentary error functions which may be computed using standard subroutine packages. Exact expressions for nonuniform currents are available for the two special cases of half-planes and infinite planes. Closed-form expressions for the axial electric field, and hence all the field components in the vicinity of the wedge axes, are also obtained. Currents computed using expressions obtained are compared with currents computed from the eigenfunction solution of the wedge, with good agreement throughout     

Equivalent currents for second-order diffraction by the edges of perfectly conducting polygonal surfaces

Equivalent, electric and magnetic, edge currents for arbitrary aspects of observation are derived for second-order diffraction by the edges of perfectly conducting, flat, polygonal surfaces. The physical model underlying the derivation is that each illuminated rectilinear edge segment excites a fringe current on the surface, acting as if it were part of an infinite straight edge. The surface wave associated with this fringe current traverses the surface along the grazing diffracted rays until it strikes an opposite edge segment, and its illumination area on the surface is delimited according to the finite length of the initiating edge segment. The "ray coordinate" measured along a grazing diffracted ray is chosen as the integration variable complementary to the edge coordinate in the fringe current radiation integral. The one-dimensional "radiation" integral over this coordinate is evaluated asymptotically in the high-frequency limit and reduced to the sum of two endpoint contributions. The upper integration limit contribution is east in the form of equivalent edge currents pertaining to the termination point of the grazing diffracted ray. These currents are responsible for the dominant part of the second-order edge diffraction. Their expressions incorporate the well-known Fresnel function (which in many eases may be replaced by its asymptotic approximation) and are finite for any combination of incidence and scattering directions, except when both of them coalesce with the grazing diffracted ray. The developed method applies both to flat plates and to plane faces of thick bodies. Examples of backscatter calculations for flat plates are given which exhibit certain improvements over previous calculations by Sikta, as compared with measured data.