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Title: Full Nov 2004 Journal Issue
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 5823 KB

Title: Nov 2004 Front/Back Matter and Index
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 1107 KB

Title: Development and Application of a Fast Multipole Method in a Hybrid FEM/MoM Field Solver
Abstract: Hybrid FEM/MoM methods combine the finite element method (FEM) and the method of moments (MoM) to model inhomogeneous unbounded problems. These two methods are coupled by enforcing the continuity of tangential fields on the boundary that separates the FEM and MoM regions. When modeling complex geometries with many elements on the boundary, the MoM part of the problem is the bottleneck of the hybrid method since it requires O(N^2) memory and O(N^3) computation time. This paper presents a hybrid FEM/MoM formulation applying the fast multipole method (FMM) that greatly reduces the memory requirement associated with MoM part. Two practical electromagnetic problems are presented to validate this method.
Author(s): C. Guo, T. H. Hubing
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 495 KB

Title: Inverse Scattering of a Dielectric Sphere Partially Buried in a Ground Plane Using a Radial Basis Function Network
Abstract: An analytic solution of the problem of electromagnetic scattering by a dielectric spherical scatterer resting on, or partially buried in, an infinite perfectly conducting ground plane is approximated by partially truncated sphere and is formulated using the method of images. The scattered field coefficients are solved exactly so that the scattered field can be evaluated everywhere. In particular, the scattering cross section can be calculated as a function of the sphere radius and permittivity as well as the truncated sphere distance for any specified angle of incidence. The solution of this problem is relevant to analyze the scattering by complex threedimensional bodies, plastic mines, icebergs, rough surfaces, etc., in which the flat background can be modeled by the ground plane while the complex body can be simulated by a sphere or a system of spheres partially truncated and resting on the ground plane. In order to solve the inverse scattering problem, we employ a radial basis function network to take the scattered field complex coefficients for the TE and TM polarization case as the network inputs to predict the three outputs of the electrical radius, burial distance, and relative permittivity of the sphere. The trained network is able to retrieve the three aforementioned parameters from new data which is different from the learning data.
Author(s): C. Loo, M. Hamid
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 1473 KB

Title: Recent Advances in Sensitivity Analysis with Frequency-Domain Full-Wave EM Solvers
Abstract: This paper introduces recent developments in efficient sensitivity analysis with numerical electromagnetic solvers in the frequency domain. We start by reviewing our original discrete approaches for sensitivity analysis. We then propose and investigate, for the first time, two new discrete approaches which enhance the accuracy of the estimated derivatives. All four introduced approaches are based on the adjointvariable method and target solvers on structured grids. Discussion and comparison of the accuracy and convergence for the different approaches are also given. Examples include waveguide and printed structures.
Author(s): S. M. Ali, N. K. Nikolova, M. H. Bakr
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 256 KB

Title: Advanced FVTD Simulation of Dielectric Resonator Antennas and Feed Structures
Abstract: This paper illustrates the application of the Finite- Volume Time-Domain (FVTD) method to the electromagnetic modeling of complex 3D antenna structures. The FVTD algorithm solves Maxwell's equations in a conformal polyhedral mesh, therefore permitting an accurate approximation of curved surfaces and a fine resolution of structural details. The flexibility of the unstructured mesh is coupled with a geometry-matched local time-stepping scheme to increase the computational efficiency. The FVTD algorithm is applied here to simulate probe-fed hemispherical dielectric resonator antennas. Emphasis of the investigation is placed on the modeling of fabrication details and their influence on the input impedance and resonance frequency of the device.
Author(s): C. Fumeaux, D. Baumann, R. Vahldieck
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 861 KB

Title: ANALYSIS OF A SUSPENDED STRIP IN A CIRCULAR CYLINDRICAL WAVEGUIDE
Abstract: The separation of variables method along with transformation theorem form Mathieu functions to Bessel functions are employed here to analyze the problem of a suspended strip in a circular waveguide. An infinite dimensional determinant is obtained which represents the characteristic equation of the proposed structure. To obtain the cutoff wavenumbers for both TE and TM cases of such a structure, the infinite determinant is truncated and convergence was observed. Numerical results for cases of interest are then presented.
Author(s): H. A. Ragheb, E. Hassan
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 375 KB

Title: RCS of Two Lossy Dielectric Loaded Semi-Elliptic Channels in a Conducting Plane
Abstract: Analytical solution to the problem of scattering of a plane electromagnetic wave by two lossy dielectric loaded semielliptic channels in a conducting plane is investigated using an iterative procedure to account for the interaction fields between the channels. The incident, scattered and transmitted fields in every region are expressed in terms of complex Mathieu functions. The translation addition theorem is used to compute the higher order scattered fields. Numerical results are presented for the far scattered field for different axial ratios, electrical separation distances, angles of incidence and loss of dielectric materials.
Author(s): A-K. Hamid
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 341 KB

Title: DESIGN OF CIRCULAR POLARIZED ANTENNAS USING GENETIC ALGORITHM BASED ON CURVED WIRE ANALYSIS
Abstract: An efficient Method of Moments formulation using curved segmentation (MoM-CS) to model curl and helical antenna structures is implemented and compared to straight wire segmentation code. This integral equation solver is then employed in conjunction with genetic algorithm (GA) to design and optimize complex helical wire antennas such as Tapered Single Helical Antenna (TSHA), Single Elliptical Curl Antenna (SECA) and Tapered Quadrifilar Antenna (TQFA) mounted over infinite ground plane. An optimum gain, VSWR and circular polarization properties that make these antennas suitable to be used in satellite communications systems are obtained. The numerical results show that the hybrid GA/ MoM-CS produces superior antenna designs for such complex geometries with reduced computation time compared to codes that use straight wire segmentations.
Author(s): M. A. Mangoud
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 416 KB

Title: Comparison of return loss calculations with measurements of narrow-band microstrip patch antennas
Abstract: The return loss of rectangular, single layer, coax fed patch antennas designed to resonate at 1904 MHz was computed using WIPL-D and HFSS and the results compared with experiment. Both codes predicted the bandwidth at 10 dB return loss points with good accuracy but not the resonant frequency and the corresponding return loss. It was also found that the resonant frequency predicted by WIPL-D was substantially closer to the experimental value than that predicted by HFSS.
Author(s): H. Abdallah, W. Wasylkiwskyj, K. Parikh, A. Zaghloul
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 279 KB

Title: ADAPTIVE NEURO-FUZZY INFERENCE SYSTEM FOR COMPUTING THE RESONANT FREQUENCY OF CIRCULAR MICROSTRIP ANTENNAS
Abstract: A new method for computing the resonant frequency of the circular microstrip antenna, based on the adaptive neuro-fuzzy inference system (ANFIS), is presented. A hybrid learning algorithm is used to identify the parameters of ANFIS. The results of the new method are in excellent agreement with the experimental results reported elsewhere.
Author(s): K. Guney, N. Sarikaya
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 224 KB

Title: MODELISATION OF PROBE FEED EXCITATION USING ITERATIVE METHOD
Abstract: This paper presents an implementation of an iterative method based on the waves concept for analyzing patch antennas fed by coaxial probes. This method includes a two-dimensional fast Fourier transform (FFT-2D) in a wave guide environment. The method has the advantage of simplicity in that it does not involve basis functions and inversion of matrices, as used in other calculation methods. Therefore, it is capable of analyzing larger bodies than other classical techniques. An implementation of the iterative calculation is shown for the extraction of S parameters of microwave components and antennas. The good agreement between simulation results and experimental published data justifies the design procedure and validates the present analysis approach.
Author(s): H. Zairi, A. Gharsallah, A. Gharbi, H. Baudrand
File Type: Journal Paper
Issue:Volume: 19      Number: 3      Year: 2004
Download Link:Click here to download PDF     File Size: 416 KB