Plane wave scattering by slots on a ground plane loaded withsemicircular dielectric cylinders in case of oblique incidence andarbitrary polarization

Plane wave scattering by single or double slots loaded with semicircular dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. To this end, systems of singular integral-integrodifferential equations of the first kind are constructed and discretized on the basis of recently developed algorithms. Several internal tests and extensive comparisons with available results were made in order to validate the numerical codes. Plotted results both for the surface magnetic current densities and the radar cross sections reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure     

Diffraction of plane waves by a strip in an unbounded gyrotropic orbiisotropic space: oblique incidence

Diffraction of plane waves obliquely incident on a perfectly conducting strip of infinite length, which is embedded in an unbounded gyrotropic or biisotropic space, is studied. To this end, a system of two singular integral-integrodifferential equations of the first kind is derived following two different methods. This system is efficiently discretized independently using two recently developed direct singular integral equation techniques. Analytical expressions are presented for the far- and near-scattered fields, along with typical numerical results     

Electromagnetic wave scattering by an infinite plane metallicgrating in case of oblique incidence and arbitrary polarization

A novel spectral-domain method combined with a sampling theorem is applied to the rigorous analysis of this quasi-two-dimensional problem. The accuracy and convergence of the method are examined numerically taking into account errors in comparison with extrapolated values, errors in the power relation, and the duality relationship. It is found that the numerical results exhibit good convergence. Another formulation related to Babinet's principle is discussed, and a relationship between the fields of an original and its complementary gratings is demonstrated. Numerical calculations are carried out showing that the method provides precise numerical results not only for the far fields, such as transmitted and reflected powers, but also for the near fields, such as surface current distribution on a strip and electric field intensity in a slit. Some numerical results related to the dual problem are provided     

Diffraction of cylindrical and plane waves by an array of absorbinghalf-screens

Multiple forward diffraction past an array of many absorbing half-screens whose separation is large compared to wavelength is examined. Starting with the physical optics approximation for half-planes that are equally spaced and of equal height, the field incident on successive edges is represented by a multidimensional Fresnel integral, which is then expanded into a series of functions studied by Boersma (1978). When the angle of incidence with respect to the plane containing the edges is small, each edge is in the transition region of the previous edge, which precludes the use of the geometrical theory of diffraction and related asymptotic theories. The solution obtained applies for incidence either from above or below the plane containing the edges, and is especially suited to the case of near-grazing incidence. This method of solution allows for numerical evaluation of a large number of half-screens and shows how the multiple diffracted fields are influenced by the physical parameters. Both incident plane waves and incident cylindrical waves can be treated     

Plane-wave scattering by strip-loaded circular dielectric cylindersin the case of oblique incidence and arbitrary polarization

Plane-wave scattering by strip-loaded circular, multilayered dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. The problem is formulated via systems of singular integral-integrodifferential equations of the first kind which are most efficiently discretized on the basis of previously developed analytical algorithms. Several internal tests along with extended comparisons with available results have been completed to validate the numerical codes. Plotted results for both the induced surface current densities and the total radar cross section reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure     

Diffraction of a plane electromagnetic wave by a two-layer finite array of small bodies of revolution

A three-dimensional vector problem of plane-wave diffraction by a two-layer finite array of perfectly conducting bodies of revolution is considered. The problem is solved under the assumption that the sizes of the elements of the array are small as compared to the wavelength. The approach proposed was tested by comparing the far-field patterns of an array with a small number of elements, calculated by two different methods. Angular dependences of the far-field patterns of arrays of elements in the form of spheres, oblate spheroids, and superellipsoids of revolution are constructed. Dependences of the plane-wave reflection and transmission coefficients on the angle of incidence for single-row finite and infinite arrays are presented.     

Diffraction of an arbitrary plane electromagnetic wave by a half-plane

The asymptotic form of the diffracted field produced by a plane electromagnetic wave of arbitrary polarization incident obliquely on a conducting half-plane is expressed very simply in terms of the incident and reflected wavesF_{1}andF_{2}, respectively, rotated to bring their wave vectorsk_{1}andk_{2}onkin the direction of observation. The diffraction coefficients becomepm(sin psi_{i}/2)^{-1}wherepsi_{i}is the angle betweenk_{i} (i = 1,2)and the direction of observationk.     

Diffraction by a half-plane with two face impedances uniform asymptotic expansion for plane wave and arbitrary line source incidence

A uniform asymptotic expansion (UAE) of Maliuzhinets' exact solution for incident plane wave diffraction by a half-plane with two face impedances has been obtained using Van der Waerden's method. This solution has been further extended to the case of arbitrary line source incidence using a heuristic approach.     

Analysis of an array of line sources above a finite ground plane

A simplified analysis which gives insight into and physical interpretation on the radiation mechanism of an array of line sources above a finite ground plane is presented. Computations have been restricted to an array of two line sources since data are available for comparison. Results on the variation of the maximum field intensity, the angle of maximum field intensity, and the field intensity at the axis of the counterpoise as functions of the size of the ground plane are presented. Variations of the maximum field intensity and the angle of maximum field intensity as functions of the distance of the source above the ground plane are also illustrated. These data become very important in the design of antennas for aircraft navigation taking into account the presence of the finite counterpoise which otherwise could lead to erroneous designs.     

Diffraction of plane and cylindrical waves by a metamaterial cylinder

Rigorous solution of the problem of plane- and cylindrical-wave scattering by a circular cylinder made from a metamaterial is presented. It is shown that, inside a metamaterial cylinder, a symmetric caustic of refracted geometrical-optics rays with one cuspidal point is formed. The influence of the position of a cylindrical-wave source and the absolute value of the refractive index of the metamaterial both on the scattering pattern and the near field structure is studied.     

Application of finite-integral technique to electromagneticscattering by two-dimensional cavity-backed aperture in a ground plane

We analyze the electromagnetic scattering by a cavity-backed two-dimensional (2-D) aperture in a ground plane illuminated by either a TE or TM plane wave. The analysis is based on the well-known generalized network formulation. To obtain the admittance matrix of the cavity, the cavity is modeled by triangular cylinders. Also, in order to specify inhomogeneous materials, a separate ϵ and μ may be assigned to each cylinder. Further, the cavity is analyzed by applying the finite-integral technique (FIT), which results in a spurious-free solution. Finally, numerical examples are presented to illustrate the applicability of the method     

Currents induced on a conducting halfplane by a plane wave at arbitrary incidence

Based on Sommerfeld's exact solution for the diffraction of a uniform plane wave by a perfectly conducting halfplane, expressions are given for the current density induced on both sides of the plane for a wave arriving at a general angle of incidence. Polarisation of the incident wave both parallel and transverse to the edge is considered. For both polarisations, computed results are presented of the magnitude and phase of the induced currents on both sides of the plane; angles of incidence over the complete range 0° to 180° are considered.     

FDTD simulation of TE and TM plane waves at nonzero incidence in arbitrary Layered media

Plane wave scattering is an important class of electromagnetic problems that is surprisingly difficult to model with the two-dimensional finite-difference time-domain (FDTD) method if the direction of propagation is not parallel to one of the grid axes. In particular, infinite plane wave interaction with dispersive half-spaces or layers must include careful modeling of the incident field. By using the plane wave solutions of Maxwell's equations to eliminate the transverse field dependence, a modified set of curl equations is derived which can model a "slice" of an oblique plane wave along grid axes. The resulting equations may be used as edge conditions on an FDTD grid. These edge conditions represent the only known way to accurately propagate plane wave pulses into a frequency dependent medium. An examination of grid dispersion between the plane wave and the modeled slice reveals good agreement. Application to arbitrary dispersive media is straightforward for the transverse magnetic (TM) case, but requires the use of an auxiliary equation for the transverse electric case, which increases complexity. In the latter case, a simplified approach, based on formulating the dual of the TM equations, is shown to be quite effective. The strength of the developed approach is illustrated with a comparison with the conventional simulation based on an analytic incident wave specification with half-space, single frequency reflection and transmission for the edges. Finally, an example of a possible biomedical application is given and the implementation of the method in the perfectly matched layer region is discussed.     

Diffraction of plane waves by a resistive strip residing between two impedance half-planes

A uniform asymptotic solution is presented for the diffraction of E_z polarized plane waves by a resistive strip residing between two impedance half-planes. The analysis proceeds from triple integral equations approach which leads to a system of uncoupled modified Wiener-Hopf equations (MWHE). This system is then reduced to two pairs of Fredholm integral equations of the second kind which are solved by successive approximations. Diffracted field expressions are derived up to the third order terms which include the surface wave field effects in a uniform manner.     

Diffraction of plane and cylindrical waves by a cylindrical metamaterial shell with a negative refractive index

The problems of scattering of plane and cylindrical waves by a cylindrical metamaterial shell are solved rigorously. The influence of the geometric dimension of the shell, the value of the negative refractive index of the metamaterial medium, and the location of the cylindrical wave source on the near (far) field structure is investigated. It is shown that, in the quasi-opticl region, a caustic with one cusp is formed inside an electrically thick shell and whispering-gallery waves or standing waves are formed in between the facets of an electrically thin shell. It is found that, in the resonance region, reactive (surface) fields with substantial amplitudes are observed near the boundaries of a thin shell.     

基于平面波斜入射的人体信道远场路径损耗建模

人体信道路径损耗计算对植入式通信链路预估具有重要意义.文章利用有耗媒质的电磁场边界条件、反射和透射定理并引入切向等效波阻抗定义,推导出平面波向人体斜入射时各人体组织分界面上的入射角、透射角、反射系数、透射系数、切向等效波阻抗以及各人体组织中的电磁合成波,提出了一种基于平面波向多层有耗媒质斜入射的人体信道远场路径损耗解析模型.然后以植入在肌肉为例,计算了TM波和TE波在5个常用工业通信频率以不同角度斜入射的人体信道电磁场分布与路径损耗,结果显示,电磁波在入射面的反射是影响人体信道路径损耗的关键因素,当频率在1.4 GHz附近时总路径损耗最小,TM波性能优于TE波,且当入射角小于等于30°时,总路径损耗基本保持不变.最后采用COMSOL Multiphysics建立了有限元仿真模型验证解析模型,二者结果高度吻合,最大误差仅为0.039,有力证明了解析模型的正确性和有效性.     

Electromagnetic plane wave scattering by large and finite strip array on dielectric slab

Plane wave scattering from a large but finite strip array on dielectric substrate is analysed in the frequency domain via a decomposition into plane wave spectra by using the method of moments and a closed analytical form of the spectral Green’s function for the structure under examination. Closed form asymptotic expressions are developed for mutual coupling terms which lead to a highly efficient and accurate procedure. New results for radar cross section in the ultra-wideband frequency range of the finite strip array are shown. Influence of the resistivity of the strips in the variation of the radar cross section is noted and discussed. Variations of the radar cross section with the scattering angle are presented as well.     

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.