TM scattering from slits in thick parallel conducting screens

TM-wave scattering from slits in thick parallel conducting screens is analyzed using the Fourier transform. The simultaneous equations for the modal coefficients are formed in terms of convergent series. Numerical computations are performed to illustrate the behavior of transmission and scattering from the slits. High-frequency solutions for scattering and transmission are obtained in approximate closed forms     

Scattering and radiation from planar structures containing smallfeatures using a finite element-fast integral method

Fast integral equation algorithms such as the adaptive integral method (AIM) have been demonstrated to reduce memory and execution time associated with moment method solutions for computing electromagnetic scattering and radiation from arbitrarily shaped three-dimensional geometries. The authors examine the efficiency of AIM in modelling planar structures that contain small and intricate details as is the case with spirals and slot antennas. Such geometries require high tessellation due to the inclusion of very small features resulting in a large number of unknowns. The AIM, with its ability to translate the original grid into an equivalent sparser uniform grid, is uniquely suited to the analysis of such geometries. The application of the AIM in connection with finite element-boundary integral formulation for cavity-backed antennas is also presented     

Wave penetration through slits on stacked thick plates

Wave penetration through slits on single and stacked metal plates of finite thickness is studied by using the Galerkin method. The limiting case of slits on infinitesimally thin plates are also formulated to compare the shielding effectiveness of metal plates with slits against incident plane waves. It is observed that the wave penetrating through slits on stacked plates with a proper separation is much less than that through a single slit on a plate with twice the thickness     

Scattering from a dielectric of finite length

The purpose of this work is the treatment of the problem of scattering from a finite length dielectric cylinder with dimensions comparable to the wavelength of the incident field. This is a general consideration of the problem, in contrast with previous papers which deal with infinite or thin scatterers or simple polarizations. To handle the problem, the integral equation approach and the dyadic analysis are used. The numerical treatment is based on the method of moments, and results are obtained for the case of broadside incidence at three different frequencies.     

Scattering from finite thickness resistive strip gratings

An analysis is presented of scattering from gratings composed of thin strips of resistive sheet material (more generally, impedance sheet material), that is characterized by an induced current in the sheet which is proportional to the tangential electric field at the sheet. The analysis make use of Galerkin's method and a spectral-domain expansion along the direction(s) of periodicity. The technique is numerically efficient for a broad class of two- and three-dimensional grating problems. The specific structures considered here are of constant cross section and consequently the scattering problems are two-dimensional     

Scattering from a finite array of microstrip patches

A full-wave solution to the problem of plane wave scattering by a finite array of rectangular microstrip patches printed on a grounded dielectric slab is presented. The electric field integral equation is solved using the spectral-domain Green's function/moment method approach. Derivations for the elements of the impedance and voltage matrices are presented. An efficient massively parallel computer implementation of the moment method solution is described. Computed radar cross section (RCS) data for microstrip patch antenna arrays are presented as a function of incident signal frequency and angle of incidence     

Scattering from conducting finite cylinders with thin coatings

The surface equivalence principle is used to develop an integral equation formulation for electromagnetic scattering from open circular cylinders with thin material coatings. The method of moments with entire domain functions leads to an algebraic system of equations which is solved numerically. Results of calculations for various cylinder aspect ratios, layer thicknesses, and material constitutive properties are presented.     

Electromagnetic scattering and radiation from finite microstripstructures

Two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures. The two techniques are based on two different formulations, viz. the volume-surface and surface-surface formulations. In the volume-surface formulation the finite-sized dielectric is replaced by an equivalent volume polarization current whereas the conducting plates are replaced by equivalent surface currents. For the surface-surface formulation the surface covering the dielectric volume is replaced by equivalent electric and magnetic currents and the conducting plates by surface electric currents. Both techniques can be utilized for the analysis of arbitrarily shaped finite microstrip structures. The techniques are quite accurate, and they are utilized to validate each other. Typical numerical results are presented to demonstrate the agreement between these two solution techniques     

厚金属板与台阶的散射

将每种极化的照射分解为对称与反对称照射之和，丛而将厚金属板的散射问题化为两种台阶的散射问题。用Wiener-Hopf法求得散射场的Fourier变换后，从中减去表面均匀电流的辐射场的Fourier变换，应用鞍点法即可求得棱边的散射场。根据线电流与电偶极辐射场的关系，由无限长棱边的场反推得微元的场。此结果可用于曲率不大的有限长曲棱边。     

Scattering from a finite length rod with endpoint contribution

A uniform, high frequency analysis for calculating scattering from thin, finite length cylinders is presented. The cylinder diameter is assumed to be small (on the order of a wavelength or less) so that the modal solution is valid. The total field consists of the incident field, the scattered field from the specular point, and two endpoint contributions. A thin wire tip diffraction coefficient (TDC) is developed for calculating the end point contributions. The incident fields are those of a spherical source radiating throughout space. While the specularly scattered field and end point contributions are discontinuous, these discontinuities cancel each other, resulting in a uniformly continuous total field. Good agreement is obtained between measured and calculated results.     

Edge effects in finite arrays of uniform slits on a ground plane

The results obtained by modeling a linear array as an infinite periodic structure can be used for the analysis of finite arrays as the zero-order approximation of a perturbation technique. This idea is utilized to investigate the edge effects in two arrays of uniform slits fed by parallel-plate waveguides terminated on a ground plane. It is shown that the realized gain pattern of an element depends substantially upon its position in the array. This is true particularly for the deep resonance notches in the patterns which are present for certain element spacings. When the array is excited with uniform magnitude and linear phase, the aperture voltages are the superposition of a term, corresponding to the infinite array model, plus another correction term (a "spatial transient") representing the edge effect. The influence of this term is particularly relevant when the array is scanned at endfire. In such a case, the method introduced here allows the prediction of the element terminal admittances and the array pattern, while according to the infinite array model no radiation would be permitted.     

Superdirective radiation from finite gratings of rectangulargrooves

In this paper, the superdirective property of arrays comprising a finite number of rectangular grooves is studied by using the modal approach, which is a simple but powerful technique for analyzing these gratings. Numerical results show that when a specific characteristic mode of the structure referred to as the π mode is excited, the intensity of the field scattered in the specular direction exhibits a maximum, which becomes sharper and narrower as the number of grooves is increased. The far-field patterns exhibit superdirectivity at these resonant frequencies as evidenced by their beamwidths that are narrower than those expected from apertures of comparable size. The model-based parameter estimation (MBPE) technique has been employed to help locate extremely narrow resonances that are characteristic of superdirective arrays and its usefulness has been demonstrated     

Scattering by a thick off-centered circular iris in circularwaveguide

A formally exact solution is described for the problems of scattering at a junction between two circular waveguides with their axes offset and at a thick off-centered iris in a circular waveguide. The analysis method uses Graf's addition theorem for cylindrical functions and the conservation of complex power technique (CCPT). Sample numerical results are presented and compared with available data in the literature     

Scattering from finite array of microstrip patches on uniaxial substrate

The problem of plane wave scattering by a finite size array of rectangular microstrip patches printed on a uniaxially anisotropic substrate is considered. Computed radar cross-section data for microstrip patch antenna arrays are presented as a function of array size, incident signal frequency, and anisotropy.<>     

Scattering and radiation from a slitted parallel-plate withrectangular grooves: TE-wave

TE-wave scattering and radiation from a slitted parallel-plate waveguide with rectangular grooves is considered. The Fourier transform and the mode matching are used to represent the scattered field in terms of the continuous and discrete modes. The simultaneous equations for the discrete modal coefficients are obtained by matching the boundary conditions. The fast-converging series solutions are presented to evaluate the far-zone radiation, reflection, and transmission coefficients. The numerical computations illustrate the angular behavior of far-zone radiation in terms of the slit size, groove size, and operating frequency. The antenna radiation pattern of the slitted parallel-plate is measured and compared with theory     

Scattering from finite by infinite arrays of slots in a thinconducting wedge

The radar scattering from a finite by infinite array of slots cut into a thin conducting wedge is considered. The wedge is formed by taking a thin ground plane and applying a bend to create a sharp edge which is parallel to the columns of slots in the infinite axis. Results are derived for thin linear slots whose major axes are either parallel or perpendicular to the edge. A hybrid moment method and geometrical theory of diffraction approach is used, with magnetic current expansion functions defined using Floquet's theorem on single columns of slots. Predictions generally agree with scattering measurements of finite by finite array physical models with monostatic patterns taken in a plane orthogonal to the sharp edge     

Scattering from finite extent frequency selective surfaces illuminated by arbitrary sources

A method is proposed for the computation of the field scattered from a dichroic plate placed in the near-field region of the feeds. The primary pattern of the feed and dichroic plate assembly has been computed.     

Image radiation from a finite ground plane in two dimensions

A simple expression for the image radiation of an array of line sources parallel to a conducting strip is derived, in terms of the known image radiation from the same sources above an infinite ground plane. Simple criteria are presented for the minimum strip width which will produce essentially the same image radiation as an infinite ground plane, for angles above the strip plane greater than some prescribed value.     

非朗伯面目标对复杂背景红外辐射的散射特性

研究了非朗伯面目标对复杂背景(太阳和海天背景)红外辐射的散射特性.基于双向反射分布函数(BRDF),通过坐标变换、对面元求和以及对波长积分等操作导出了非朗伯面目标散射亮度的空间分布式.利用海天背景的光谱亮度和太阳光谱照度(由大气传输软件Modtran计算),以及目标表面的光谱BRDF,以圆柱体为例,分别对3～5 μm和...     

Scattering by arbitrarily-shaped slots in thick conducting screens: an approximate solution

In this paper, the integral equation formulation of the thick aperture problem is reviewed and then modified to make it continuously valid for any aperture thickness. Hence, the new proposed thick aperture formulation is free from the difficulties usually encountered when applying it to a vanishing thickness slot. Afterwards, a simplification of the formulation is proposed, which reduces dramatically the computational burden while providing valid results for apertures whose thicknesses remain small compared with their linear transverse dimensions but having otherwise arbitrary shapes and sizes. Preliminary numerical results confirm the validity of the proposed technique and show clearly its advantages.