Scattering by two-dimensional lossy, inhomogeneous dielectric andmagnetic cylinders using linear pyramid basis functions and pointmatching

A volume integral equation approach is used to calculate the scattering characteristics of lossy, inhomogeneous, arbitrarily shaped, two-dimensional dielectric and magnetic bodies. The scatterer is divided into triangular patches, which simulate curved and piecewise linear boundaries more closely than circular cylinder cells. Linear pyramid basis functions are employed to expand the unknown total electric field at the triangle nodes. The enforcement of the boundary conditions by point matching at the nodes converts the electric field integral equation to a matrix equation. Example cases are run and compared to previous moment methods and exact solutions, and this method shows good agreement. This method requires only one unknown per node in dielectric and magnetic material, which is a significant reduction in unknowns and matrix storage compared to traditional methods. By duality, this method can be used at either transverse electric or transverse magnetic polarization     

MMW scattering by rough lossy dielectric cylinders and tree trunks

The millimeter-wave (MMW) radar backscatter response of a rough, lossy, dielectric cylinder is examined both analytically and experimentally. Models for both the coherent and incoherent components of the scattered field are developed based on the geometric-optics approximation. The accuracy of the analytical models and their applicability in predicting the backscatter response of tree trunks are determined experimentally by measuring the radar backscatter at 95 GHz from a rough conducting cylinder and from a section of a tree trunk. In both cases, very good agreement was achieved between the model predictions and the measurements     

Scattering by a lossy dielectric cylinder in a rectangularwaveguide

Electromagnetic fields in a rectangular waveguide containing a lossy dielectric cylinder are investigated by means of the orthogonal expansion method. The calculated results are provided by measurement. Resonance effects become visible through the frequency responses of the scattering parameters and understandable by patterns due to magnetic fields and Poynting vectors. The lowest resonance is nonsymmetric and can be used to realize tunable bandstop filters with a relative 3-dB bandwidth of about 0.04 and an attenuation of more than 40 dB     

Scattering by a lossy dielectric circular cylindrical multilayer numerical values

The theoretical scattering solution for a plane wave incident normally on a lossy dielectric multilayer circular cylinder of infinite length is outlined. Numerical values of the modal scattering coefficient for TE and TM modes are given for several single and multilayer cylinders. Verifications of the results are described. The values may serve as reference data.     

An improved MFIE formulation for TE-wave scattering from lossy,inhomogeneous dielectric cylinders

A method-of-moments formulation involving the magnetic-field integral equation (MFIE) is presented for the analysis of nonhomogeneous electric (TE) source. The approach involves the use of triangular subdomain cells, a piecewise linear expansion for the total magnetic field, and point matching at the nodal points of the triangular-cell model. Results for internal fields and radar cross section are presented and shown to be stable and convergent, even for dielectrics characterized by a large-magnitude complex relative permittivity. It is noted that the complementary problem of TM-wave scattering from ferrite cylinders characterized by a permeability function can be treated using the dual to the approach presented     

Scattering of electromagnetic waves by arrays of conducting and dielectric cylinders

A method is developed that enables the solution of scattering by a finite number of cylinders in a convenient and accurate form. It is based on an analytic formulation using the boundary value problem and an application of a point matching technique. The method is then applied to study the scattering properties of both conducting and dielectric cylinders. It is also used to determine the size and spacing of passive scatterers to improve the directivity of linear antennas. In the latter case, a combination of the present method and a space perturbation technique is utilized to optimize the antenna gain.     

Scattering of a dipole field by finitely conducting dielectric circular cylinders

Using the differential equation approach an exact formal solution for the fields due to an axial electric dipole in the presence of a homogeneous isotropic infinite circular cylinder is obtained in integral form. An asymptotic expansion of the integral yields the far field. Patterns for different choices of the parameters are given. It is seen that for dielectric cylinders in particular, drastic departures from the perfectly conducting case can be obtained leading to more directive patterns. This in turn may have application in the design of arrays.     

Scattering by perfectly-conducting rectangular cylinders

The problem of determining the fields scattered by a perfectly-conducting rectangular cylinder is reduced to the solution of an integral equation. This equation is then solved by digital computer methods. Data are given for surface currents, radiation patterns and scattering cross sections for bothE- andH-incident waves.     

Wide-band electromagnetic scattering from a dielectric BOR buriedin a layered lossy dispersive medium

A method of moments (MoM) analysis is developed for electromagnetic scattering from a dielectric body of revolution (BOR) embedded in a layered medium (the half-space problem constituting a special case). The layered-medium parameters can be lossy and dispersive, of interest for simulating soil. To make such an analysis tractable for the wide-band (short-pulse) applications of interest here, we have employed the method of complex images to evaluate the Sommerfeld integrals characteristic of the dyadic layered-medium Green's function. Example wide-band scattering results are presented, wherein fundamental wave phenomenology is elucidated. Of particular interest, we consider wide-band scattering from a model plastic mine, buried in soil, with the soil covered by a layer of snow     

Scattering by dielectric containers

The radar cross section (RCS) has been derived by an approximate method for a thin dielectric plate and for thin spherical and conical dielectric shells. The computed results for a flat plate and a conical shell are compared with experimental patterns. The computed results for a conical shell are presented in the form of constant RCS contours on the aspect angle-frequency plane.     

Scattering by parallel conducting circular cylinders

The multiple scattering by two parallel conducting circular cylinders is considered. The total scattered field is divided into two components, namely a noninteraction term and a term due to all interactions between the cylinders. The noninteraction term is expressed exactly, whereas the interaction field is evaluated using the method of moments. It is found that this technique leads to an efficient solution for both the monostatic and bistatic scattering by cylinders of large radii. The computational advantages of this technique over classical boundary value and numerical solutions are presented.     

Scattering by multilayer isorefractive elliptic cylinders

An analytical solution to the plane-wave electromagnetic scattering by multilayer elliptic cylinders is derived in the case of isorefractive materials. For these materials, a recursive solution similar to the solution for the multilayer circular cylinder is obtained. Moreover, it will be shown that the matrix-based recursive procedure for common dielectrics reduces to the present solution in this particular case. Finally, a number of numerical examples and comparisons will be provided.     

On the quasi-TEM and full-wave approaches applied to coplanarmultistrip on lossy dielectric layered media

The characteristic parameters of coplanar multistrip lines embedded in multilayered lossless/lossy substrates are commonly computed by using either quasi-TEM or full-wave model. Several methods are provided in the literature to deal with this type of structure. A comparative study of quasi-TEM and rigorous solutions is carried out in order to establish criteria for the validity of the quasi-TEM approach. Reliable quasi-TEM and full-wave numerical data have been properly generated by applying an enhanced spectral domain analysis. The authors conclude that the quasi-TEM model yields satisfactory results for many MIC and MMIC practical cases. However, significant errors arise when high conductivity substrates are involved in MMIC applications. A discussion about the computation of the dynamic modal characteristic impedance is also reported, showing how the insertion of the modal orthogonality can save computational effort in a lossy multiport system     

Scattering by finite, open cylinders using approximate boundaryconditions

Simplified integral equation formulations for electromagnetic scattering from finite, open, circular cylinders are developed by invoking approximate boundary conditions. The approximate calculations are compared to calculational results of formulations based on exact boundary conditions. It is shown that the approximations work quite well despite the curved edges of the cylinders     

Scattering from a metallic object embedded near the randomly roughsurface of a lossy dielectric

Two-dimensional electromagnetic scattering from a perfectly conducting target embedded near the randomly rough surface of an isotropic lossy dielectric is investigated. The randomly rough surface is illuminated by a finite width beam from an antenna in the free space above the surface, with off-normal incidence. Standard integral equation methods are applied and include all subsurface interactions between the object and rough surface. For a chosen embedded target, Monte Carlo simulations are performed for a selection of ensembles of rough surface types intended to be suggestive of natural ground. Far field scattering coefficient distributions and corresponding synthetic images suggest when the buried object should be discernible. Sensitivities are explored in terms of surface type, polarization of the incident field, depth and orientation of target, soil characteristics, incidence angle, and beamwidth. Many of the scattering features identified should also apply in 3D     

Electromagnetic scattering by inhomogeneous dielectric cylinders

The scattering of electromagnetic waves by inhomogeneous dielectric cylinders is formulated by the unimoment method, and the interior finite-element problem is solved in a mesh geometry that greatly increases computational efficiency. Results are presented and compared to previously reported curves.     

Scattering by thin dielectric strips

A plane wave incident on a thin dielectric strip with infinite length is considered, letting the incident electric field vector be parallel with the edges of the strip. The field is expanded in the dielectric region as the sum of three plane waves (the forced wave and two surface waves). Thex-axis andy-axis propagation constants are known for each wave, and Galerkin's method is employed to determine the amplitudes of these waves. Finally, the far-zone scattered field is determined by considering the polarization currents radiating in free space. Numerical data are presented to illustrate the scattering properties of lossless and lossy dielectric strips as a function of the angle of incidence and the width of the strip. The calculations show excellent agreement with an earlier moment method using pulse bases and point matching.     

Scattering by a rotating dielectric sphere

The scattering of a plane wave by a rotating dielectric sphere of arbitrary radius,epsilon_{r}andmu_{r}is investigated. A relativistically correct solution is found for the scattered fields and the fields inside the sphere. This solution is valid in the limit of "small" angular velocities. Attention is focused on the fields at large distances. The depolarization of the backscattered signal and the scattering in the low frequency limit are treated in some detail.     

Scattering by right angle dielectric wedge

An asymptotic solution of electromagnetic waves scattered by a right-angled dielectric wedge for plane wave incidence is obtained. Scattered far fields are constructed by waves reflected and refracted from dielectric interfaces (geometric-optical fields) and a cylindrical wave diffracted from the edge. The asymptotic edge diffracted field is obtained by adding a correction to the edge diffraction of physical optics approximation, where the correction field in the far-field zone is calculated by solving a dual series equation amenable to simple numerical calculation. The validity of this result is assured by two limits of relative dielectric constantvarepsilonof the wedge. The total asymptotic field calculated agrees with Rawlins' Neumann series solution for smallvarepsilon, and the edge diffraction pattern is shown to approach that of a perfectly conducting wedge for largevarepsilon. Calculated far-field patterns are presented and the accuracy of physical optics approximation is discussed.     

Scattering by a finite set of perfectly conducting cylinders buried in a dielectric half-space: a spectral-domain solution

An analytical-numerical technique, for the solution of the two-dimensional electromagnetic plane-wave scattering by a finite set of perfectly conducting circular cylinders buried in a dielectric half-space, is presented. The problem is solved for both the near- and the far-field regions, for TM and TE polarizations. The diffracted field is represented in terms of a superposition of cylindrical waves and use is made of the plane-wave spectrum to take into account the reflection and transmission of such waves by the interface. The validity of the approach is confirmed by comparisons with results available in the literature, with very good agreement. The multiple interactions between two buried cylinders have been studied by considering both the induced currents and the scattered field diagrams. Applications of the method to objects of arbitrary cross-section simulated by a suitable configuration of circular cylinders are shown.