Transient scattering from conducting cylinders

A method for determining the fields scattered by arbitrarily shaped cylindrical conducting structures with a transient incident wave is described. The transient scattering problem is reduced to the solution of a time domain integral equation which in turn is solved directly in the time domain by means of a digital computer. The approximate electromagnetic impulse response for a number of cylindrical scatterers is calculated using this method.     

Transient scattering by conducting surfaces of arbitrary shape

The time-domain electric field integral equation (EFIE) is used along with the method of moments to develop a simple and efficient numerical procedure for treating problems of transient scattering by arbitrary shaped conducting objects. The conducting surface is modeled by planar triangular patches for numerical purposes. Because the EFIE is used in the solution procedure, the method is applicable to both open and closed bodies. the EFIE approach is applied to the scattering problems of Gaussian plane wave illumination of a flat square plate and sphere. Comparisons of surface current densities and far-scattered fields are made with previous computations and good agreement is obtained in each case     

Oblique scattering by a pair of conducting half planes: TM case

An exact series solution for the oblique scattering by a pair of infinitely long parallel edges of perfectly conducting half planes is formulated for a TM plane wave using the mode-matching technique (MMT). The scattered and guided fields are represented in terms of an infinite series of radial waveguide modes. By applying the appropriate boundary conditions, the coefficients of the scattered field are obtained. The diffraction coefficient of double edges is subsequently derived from the scattered field     

Transient scattering by resistive cylinders

The two-dimensional scattering of an electromagnetic pulse normally incident on a collection of infinitely long cylinders of arbitrary shape is considered. ForE-polarization an electric field integral equation is derived that is applicable to solid cylinders and/or thin sheets, resistive and/or perfectly conducting. The contribution of the self-cell at later times is carefully analyzed. The expression obtained represents a generalization of previously known results. For an incident Gaussian pulse, numerical results are presented for surface currents and far-fields, for perfectly conducting and resistive circular cylinders and strips. A fast Fourier transform (FFT) algorithm is implemented to obtain the backscattering radar cross section, which is in good agreement with results obtained from either exact continuous wave (CW) solutions or the method of moments.     

Multiple scattering by two conducting circular cylinders

Multiple scattering by two conducting circular cylinders is studied by applying three different methods: the method of Zitron and Karp (ZK), the method of Karp and Russek, and an iterative method which gives the exact solution. It is found from the numerical results for the total scattering cross section that the ZK method gives very precise results even for rather largekaand smallkd, whereaanddare the radius of the cylinder and the separation between the cylinders, respectively.     

High frequency scattering by a conducting ring

Asymptotic formulae are derived for the Fourier coefficients of the thin wire kernel in the integral equation for the electric current on an electrically large, thin circular loop. The total current induced on the ring by a plane electromagnetic wave is approximated by a modified physical optics term proportional to the incident field, plus resonant terms of lossy circulating waves. Numerical evaluation of the dominant poles and residues of the ring transfer function provides the amplitudes and complex propagation constants of these natural modes.     

A wire-grid model for scattering by conducting bodies

A point-matching solution is developed for scattering by conducting bodies of arbitrary shape. Numerical results are included for the backscatter echo area of circular and square wire loops, circular and square plates, spheres, and hemispheres. The results show good agreement with experimental data. An efficient calculation procedure is achieved by using a wire-grid model instead of a continuous conducting surface. A system of linear equations is generated by enforcing the boundary conditions at the center of each wire segment of the grid, and a digital computer is employed to solve these equations for the currents on the segments. Then it is straightforward to calculate the distant scattered field and the echo area.     

Plane wave scattering by a corrugated conducting cylinder atoblique incidence

The problem of scattering from a corrugated conducting cylinder due to an obliquely incident plane wave is solved by a boundary-value method. The region between the corrugations is considered as a medium with tensor permeability and tensor permittivity, which is a valid assumption when the corrugation constant is much less than the free-space wavelength. By loading this region with a dielectric material, one of the components of the scattered electric field in the far-field region can be altered significantly with no change in the other component. These components, in turn, determine the bistatic scattering cross sections, and the dielectric loading of the corrugated region appears to have no effect on the cross section due to the polarized component, while showing significant changes in the cross section due to the depolarized component     

Plane wave scattering by a conducting elliptic cylinder coated by anonconfocal dielectric

The scattering properties of a dielectric-coated nonconfocal conducting elliptic cylinder are investigated. The theoretical treatment of such a problem is based on the boundary value solution, which is an exact treatment of the problem. Only the transverse magnetic (TM) case is considered, although the transverse electric (TE) case can be treated in the same way. It is shown that this solution is much more general than all previous solutions because it can handle a variety of scattering geometries. Numerical results are presented in graphical form for the echo width pattern of various geometries     

Electromagnetic scattering from conducting circular cylinders inthe presence of a stratified anisotropic medium-TM case

Scattering by a conducting circular cylinder in the presence of a stratified ferrite medium is investigated analytically using a combined Green's function (G-function) and integral equation approach. The incident plane wave is polarized along the axis of the cylinder. The bias DC magnetic field is in the same direction. The G-function of the structure is developed by well-known techniques of matrix analysis, and the appropriate integral equation for the electric field is derived on the basis of the modified reciprocity theorem. Its solution is followed by numerical results presented in graphical form for both the current density induced on the scatterer's surface and the scattered far field. The possibility of controlling the scattering properties of the structure by varying the degree of anisotropy is also investigated. The main conclusion is that anisotropic materials can be used to control antenna radiation characteristics     

Multiple scattering from two dielectric-filled semi-circular channels in a conducting plane: TM case

The behavior of TM-wave scattering from two dielectric-filled semi-circular channels in a perfectly conducting substrate is investigated. The scattered field is represented in terms of an infinite series of radial modes with unknown coefficients. By applying separation of variables and employing the partial orthogonality of sine functions, the unknown coefficients are obtained. The resulting infinite series is then truncated to a finite number of terms to produce numerical results. Plotted results for the radar cross sections reveal how the scattering properties may be varied by changing several physical and geometrical parameters of the structure.     

分形大气湍流中导体目标的电磁散射

提出了分形大气湍流中导体目标的电磁散射理论,导出了分形大气湍流中光滑导体目标散场的一阶矩和二阶矩。给出了平面波和球面波入射下互相关函数和结构函数随分维的变化关系。以光滑导体圆盘为例计算了其归一化后向散射截面σｎ。结果表明对于具有分形谱分布特征的大气湍流,分维对σｎ有较大影响。     

Analysis of the electromagnetic scattering by perfectly conducting convex polygonal cylinders

An effective method for the analysis of the scattering by a perfectly conducting convex polygonal cross-section cylinder is presented. The effectiveness stems from the generalization of the Neumann series, factorising the right edge behavior of the electromagnetic field, thus leading to a quickly convergent method. The induced currents, the radar cross section (RCS) and the induced field ratio have been evaluated.     

Electromagnetic scattering by a perfectly conducting patch array ona dielectric slab

The scattering characterization of an infinite and truncated periodic array of perfectly conducting patches on a dielectric slab is discussed. In particular, an approximate solution for the truncated array scattering that is based on the exact solution for the corresponding infinite array is presented. The latter is obtained numerically by solving for the patch currents using a conjugate-gradient fast Fourier transform (FFT) technique, eliminating the need to generate and store the usual square impedance matrix. The scattering pattern of the finite array is then computed approximately by integrating the infinite-period-array currents over the given finite array. Numerical results are presented for the infinite and finite arrays, and the accuracy of the approximate solution for the finite array is examined and discussed in relation to some available exact data. It is found that the approximate solution is of reasonable accuracy in predicting the scattering by the truncated array     

一种旋转对称涂覆导体电磁散射高效分析方法

为改善传统方法分析旋转对称涂覆导体电磁散射问题的效率,提出了一种高效分析方法.该方法在介质表面建立电磁流混合场积分方程(Electric and Magnetic Current Combined Field Integral Equation,JMCFIE),在导体表面建立混合场积分方程(Combined Field Integral Equation,CFIE),利用了旋转对称体在空间上的旋转周期性,只需要对表面的母线进行剖分,具有未知量少且阻抗矩阵条件数好的特点.根据等效原理与边界条件推导了JMCFIE-CFIE方程,并与传统的PMCHW-CFIE方法对比了求解效率.数值算例表明该方法能明显改善方程的收敛性.     

High frequency scattering of a Gaussian beam by a conducting cylinder

When the radius of the cylinder is much larger than the wavelength, an approximate expression for the scattering of a Gaussian beam by a conducting cylinder is obtained by using Watson transformation. The beam fields in shadow region and illuminated region are, respectively, derived from residue theorem and stationary phase method. In order to check the theory, comparisons for scattering pattern and field variation in space were made. Numerical examples of the scattering patterns forw/lambda geqleq a_{0}/lambda gg 1 (w, a_{0} lambdabeing the beamwidth, the radius of cylinder, and the wavelength) are also illustrated.     

Electromagnetic scattering by a conducting strip with a multilayerelliptic dielectric coating

The scattering of an electromagnetic plane wave by a conducting strip coated with a multilayer elliptic dielectric is considered. The solution of this problem is carried out by using an expansion of the electromagnetic field in terms of Mathieus functions and by implementing an efficient procedure for the “treatment” of the boundary conditions. This procedure could be a useful tool for checking the accuracy of numerical techniques widely used in electromagnetic compatibility, as it allows the solution of one of the few canonically solvable scattering problems involving perfectly conducting objects with sharp edges and inhomogeneous dielectrics. Many numerical results concerning the scattering cross section per unit length are provided and, where possible, they are compared with already available results. We consider only perpendicular incidence, although oblique generalization is conceptually easy