M. Hamid

Rigorous solution of the scattering by two multilayered dielectric cylinders

In this paper the scattered field due to a plane wave incident on two parallel multilayered dielectric cylinders is derived using the boundary value approach. An asymptotic solution is also presented in which fictitious line sources located at the cylinder axes are used to account for the multiple interactions. For the sake of simplicity two layered-dielectric cylinders and two dielectridy coated conducting cylinders are investigated, however the solution can be easily extended to many layers as well as to many cylinders.

Moment method solution of double step discontinuities in waveguides

The problem of scattering of a double step waveguide discontinuity is investigated. Two coupled sets of equations in terms of the unknown magnetic current sheets on the apertures are obtained and solved for the electric field distribution using the moment method. The scattering matrix coefficients describing reflection, transmission, and mode conversions at a symmetric double step waveguide discontinuity are obtained and presented graphically for specific junctions.

Iterative solution of the scattering by a system of multilayered dielectric spheres

The effect of the dielectric layers on the multiple scattering behavior is studied for a system of two dielectric spheres with concentric shells. The solution to this problem is a first step toward the more general solution for arbitrary configurations of multilayered spheres which has potential applications in the simulation of complex bodies and in electromagnetic shielding for apertureless spherical cavities. Since the iterative procedure does not require matrix inversion and only a small number of iterations is needed (two to four for the range of parameters considered), the method presented is proved to be highly efficient.<<ETX>>

Iterative technique for scattering by a linear array of spheres

A novel iterative procedure is proposed for the solution to the scattering by a system of conducting spheres. This approach requires the solution of the field scattered by each sphere assumed to be alone in the incident field, which acts as an incident field on the other spheres. Therefore, the first-order scattered field results from the excitation of each sphere by the incident field only, while the second-order scattered field results from the excitation of each sphere by the sum of all first-order scattered fields. Hence, this iterative process continues until the solution converges. One of the advantages of employing this approach is that the proposed solution does not require matrix inversion and therefore the desired scattered field coefficients are obtained after each iteration and used in the subsequent iteration. Numerical results are plotted for the normalized backscattering and bistatic cross section patterns for various electrical separations, radii, and angles of incidence.<<ETX>>

Analytic solution of scattering by an array of conducting spheres

An analytic solution to the problem of multiple scattering of a plane wave by a linear array of N perfectly conducting spheres is obtained by using the addition theorem for the vector spherical wave functions. Numerical results are presented for the normalized backscattering and bistatic cross sections for systems of spheres with different separations and radii.<<ETX>>

Near field analysis of a perfectly conducting slotted elliptic cylinder

Near-field analysis of a perfectly conducting slotted cylinder excited by an electric line source or a z-polarized incident wave is considered. The problem is reduced to an integral equation in terms of the aperture field. The solution of the integral equation is carried out by expressing the aperture field in terms of a Fourier series expansion with unknown coefficients. Then Galerkins technique is used to solve for the unknown aperture field coefficients.<<ETX>>

Electromagnetic scattering by hemispherical bosses on a infinite plane surface

An analytic solution to the problem of multiple scattering of a plane electromagnetic wave by an array of hemispherical bosses on a perfectly conducting infinite plane surface is obtained by using the solution of the scattering by an array of full spheres, on the basis of an image technique. The solution of this problem is relevant in analyzing the scattering by 3-D rough surfaces. The system considered is replaced by the array of complete spheres in the absence of the conducting plane, but with the given incident plane wave and also a supplementary image plane wave, chosen such that the boundary conditions for the total field are satisfied at all the points where the conducting plane is located in the original problem. Numerical results are presented for the normalized backscattering cross section versus the incident angle for different systems of spheres.<<ETX>>

Generalized network formulation for symmetric double-step waveguide discontinuities

The equivalence principle and the moment method, which have previously been employed in the solution of single-step waveguide discontinuities, are extended to find solutions for the field and the scattering matrix coefficients at the junctions of symmetric double-step waveguide discontinuities. Scattering matrix coefficients are computed for representative symmetric double-step waveguide discontinuities and frequencies. The method is simple and straightforward, and the results obtained are compared with data available in the literature.

Hybrid mode analysis of a conical waveguide with a radially tapered impedance wall

This article presents a new conical structure which can support the spherical hybrid modes associated with corrugated conical waveguide. The analysis closely follows that of hybrid modes in corrugated conical waveguide. It is found that in order to obtain hybrid modes in a dielectric lined conical waveguide it is necessary to taper the dielectric constant of the lining.

Multi-section transmission line transformer of arbitrary length

A simple approach for matching a purely resistive load impedance to a given transmission line is presented. The parameters of the transformer can be accurately computed from presented equations. In this approach, the length of each section, as well as the characteristic impedance, can be properly chosen in order to minimize the total length of two sections while obtaining relatively wider bandwidth compared with the case of two sections of equal length. This approach provides much shorter total length and reduces the insertion loss of the matching section, while providing almost the same bandwidth property as compared with a single quarter-wavelength transformer section.