Alaa K. Abdelmageed

Dual-polarized omnidirectional planar slot antenna for WLAN applications

A novel planar slot antenna is presented in this paper. The antenna provides dual-polarization and omnidirectional radiation patterns. Hence, it is suitable for hand-held equipments of wireless systems. The proposed antenna is optimized for operation at 5.2 GHz. The antenna, without ground plane extension, occupies an area of 2.17/spl times/2.17 cm/sup 2/. An impedance bandwidth of 10.6% is obtained, with a very good isolation between the two excitation ports. Appealing omnidirectional radiation patterns are maintained over the entire impedance bandwidth. The gains of the two polarizations are 2.59 and 3.52 dB, while the radiation efficiencies are 93% and 99.8%.

Efficient Evaluation of Modal Green's Functions Arising in Em Scattering By Bodies of ΡΕVolution - Abstract

The integral equations governing the electromagnetic scattering by bodies of revolution involve the computation of what are called the modal Greens functions. These functions are evaluated repeatedly. Hence, any saving in time while computing these functions will be reflected on the overall time of computation. These functions are usually evaluated using an adaptive numerical integration technique. In this work, an exact series form is obtained to efficiently evaluate these functions. An acceleration technique is used to speed up the series convergence. The method can be implemented in existing codes. It is shown that a significant saving in the time of computation is achieved using the series form.

Analysis of EM scattering by conducting bodies of revolution in layered media using the discrete complex image method

A mixed-potential integral equation (MPIE) is formulated for conducting bodies of revolution (BORs) embedded in plane stratified-media. The axis of BOR is assumed to be perpendicular to the material layers. The spectral integrals that arise in the MPIE kernels are efficiently evaluated by the discrete complex image method (DCIM). Sample numerical results are presented for a pillbox scatterer in a half-space environment.

On Enhancing the Accuracy of Evaluating Green's Functions for Multilayered Media in the Near-Field Region

The discrete complex image method stands as one of the most efficient techniques that is able to represent the Greens functions of multilayered structures accurately in the near- and intermediate- field regions. In order to extend the validity of the method to the far region,the surface waves are extracted. Although the extraction process yields accurate results in the intermediate and far-field regions, erroneous results are observed in the near-field region. In this paper, this problem is treated by extracting the contribution of an additional number of artificial poles. Using this scheme,the discrete complex image method can provide accurate representation of Greens functions in both the near- and far-field regions.

An Integral Equation Formulation for TM Scattering by a Conducting Cylinder Coated with an Inhomogeneous Dielectric/Magnetic Material

A volume-surface integral equation (VSIE) formulation is developed for determining the electromagnetic TM scattering by a two-dimensional conducting cylinder coated with an inhomogeneous dielectric/magnetic material. The electric fleld integral equations (EFIEs) are utilized to derive the VSIE. The surface EFIE is applied to the conducting surface, while the volume EFIE is applied to the coating region. By employing the surface and equivalence principles, the problem is reduced into a set of coupled integral equations in terms of equivalent electric and magnetic currents radiating into unbounded space. The moment method is used to solve the integral equations. Numerical results for the bistatic radar cross section for difierent structures are presented. The well-known exact series-solution for a conducting circular cylinder coated with multilayers of homogeneous materials is used along with the available published data to validate the results. The in∞uence of using coatings with double-positive (DPS) and/or double-negative (DNG) materials on the radar cross section is investigated.

Magnetic field integral equation for electromagnetic scattering by conducting bodies of revolution in layered media - Abstract

This work presents a new formulation for conducting bodies of revolution (BOR) in layered media. It is derived using magnetic field integral equation (MFIE). The discrete complex image method is used to transform the Sommerfeld integrals into closed form solutions. For large closed objects, the use of the magnetic field formulation is shown to be more advantageous than the electric field integral equation (EFIE) concerning the convergence of the solution. The obtained formulation is applied to the contiguous half-spaces case. Results of both the magnetic and electric field integral equation formulations are presented.

Electromagnetic TE scattering by a conducting cylinder coated with an inhomogeneous dielectric/magnetic material

The problem of electromagnetic TE scattering by an infinitely long conducting cylinder coated with an inhomogeneous dielectric/magnetic material is analyzed. A volume-surface integral equation (VSIE) approach is utilized to model the problem. By imposing the boundary conditions on the conducting surface, a surface magnetic field integral equation (MFIE) is developed. Inside the volume of the coating region, volume MFIEs are applied. The resultant integral equations are solved using the moment method. Numerical results for the bistatic radar cross section for different structures are presented. The results are validated using the exact series solution for a conducting circular cylinder coated with multilayers of homogeneous materials. Two types of coating materials are studied: the conventional or double positive (DPS) materials and the double negative (DNG) materials.

A New Approach to Evaluate the Surface Waves Term for the Nonsymmetrical Components of Green's Functions in Multilayered Media

The discrete complex image method is one of the most prominent techniques that handle the Sommerfeld integrals encountered in the integral equation formulations of multilayered media. The extraction of surface waves extends the validity of the method to the far field. These surface waves are expressed in terms of Hankel functions that suffers a singularity problem at the origin which contaminates the results in the near field. In this work,we use a formulation developed recently by the author to derive a new expression for the surface waves. The new expression is shown to obviate the singularity of the Hankel functions at the origin,and hence leads to accurate results in the near field.

A Closed-Form Expression of the Nonsymmetrical Components of Green's Function for Multilayered Media

The Greens function for multilayered media is expressed in terms of Sommerfeld integrals. The discrete complex image method is an appealing technique in handling such integrals. However, the results of the nonsymmetrical components lacks sufficient accuracy in the near-field region. This is due to the fact that these components have slowly varying spectral-domain behavior. In this work, the quasi-dynamic contribution is explicitly extracted. The remaining part has fast decaying behavior. The generalized pencil-of-function method is used to recast this part into a set of exponentials. Using a special identity, a closed-form expression is obtained that is valid in the near-field region. The method is demonstrated to yield accurate results for microstrip structures.

A surface integral equation formulation for electromagnetic scattering from a conducting cylinder coated with multilayers of homogeneous materials

A surface integral equation formulation is presented for electromagnetic scattering by a conducting cylinder coated with multilayers of homogeneous materials. Each layer may have a nonunity relative permittivity and permeability. Both the TM and TE polarizations are considered. The surface equivalence principle is utilized to model the problem where each layer is replaced by equivalent surface currents residing on the enclosing boundaries. A systematic procedure is developed to generate a set of coupled integral equations for an arbitrary number of layers. The method of moments is invoked to convert these equations into a sparse matrix equation which can be solved using sparse matrix routines. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method. The performance of the method is compared with that of the volume-surface integral equation formulation where a great saving in memory storage and computation time is achieved.