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Title: November 2003 Full Issue
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Front / Back Matter and Contents
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Full 2003 Special Conf. Issue
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Bistatic Scatterer And Antenna Imaging
Abstract: Two computing techniques to create an image of the radiating centres on an antenna or scatterer using Fourier optics is presented
Author(s): Steve Inge
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: An Approach to Multi-Resolution In Time Domain Based On The Discrete Wavelet Transform
Abstract: In this paper, an approach to multi-resolution in time domain (MRTD) is presented. Maxwell equations are discretized using finite differences in time and a derivative matrix in space that allows any desired level of spatial resolution. This derivative matrix acts on the coefficients that represent the expansion field components. These coeffiecents are calculated by means of the Discrete Wavelet Transforms. In this word hard (PEC and PMC) boundary conditions have been introduced into the algorithm using the method of images.
Author(s): C. Represa, C. Pereira, A. C. L. Cabeceira, I. Barba, J. Represa
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 346 KB

Title: Utilizing Particle Swarm Optimization in the Field Computation of Non-Linear Magnetic Media
Abstract: It is well known that the computation of magnetic fields in nonlinear magnetic media my be carried out using various techniques. In the case of problems involving complex geometries or magnetic media, numerical approaches become especially more appealing. The purpose of the paper is to present an automated particle swarm optimization approach using which field computations may be carried out
Author(s): A. A. Adly, S. K. Abd-El-Hafiz
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: An Empirical Approach for Design of Wideband, Probe-Fed, U-Slot Microstrip Patch Antenna on Single-layer, Infinite, Grounded Substrates
Abstract: Wideband microstrip antennas with relatively simple topologies continue to attract attention for design of compact, high-performance communication systems. The coaxially-fed rectangular patch U-slot has recently been investigated numerically and experimentally, and shown to yield 10 return-loss bandwidths in excess of 20%. However, there are no analytical models, nor any systematic design procedures currently available that can aid in realizing these confugurations. To that end, based on extensive CAD simulation results, for a wide range of commercially available microwave substrates (Er=2.94 to 10.2), and empirical design methodology is derived and illustrated by examples. It is shown that the present empirical design technique, with its attendant limitations, generate wideband U-slot designs that are optimzied using CAD tools such as IE3D within a few iterations, resulting in substantially reduced overall process cycles.
Author(s): V. Natarajan , D. Chatterjee
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Analysis of Conventional and Novel Delay Lines: A Numerical Study
Abstract: Delay lines are convenient circuit elements used to introduce delay between circuit board components to achieve required timing. Serpentine or meander lines are the most common of delay lines. These lines introduce delay but also introduce spurious dispersion that makes the signal appear as if it is arriving earlier than expected. The cause of such spurious speed-up or skew is analyzed qualitatively. Previous work found that owing to the periodicity inherent in the serpentine line structure, the crosstalk noise accumulates synchronously, thus creating a higher potential for triggering false logic. Numerical simulations are performed using the Finite-Difference Time-Domain (FDTD) method to corroborate the qualitative prediction with physical behavior. Based on the understanding of the coupling mechanism in periodic serpentine lines, a qualitative prediction can be made of the behavior of novel delay lines such as the spiral line. A new delay line, the concentric Cs delay lines, is introduced. The design of the new line is based on forcing the crosstalk noise to spread over time, or to accumulate asynchronously, thus enhancing the integrity of the received signal.
Author(s): O. Ramahi
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 174 KB

Title: Automatic Calculation of Band Diagrams of Photonic Crystals Using the Multiple Multipole Method
Abstract: In the framework of photonic crystal’s band structure calculations, we present a novel way – based on several advanced techniques for searching and tracing eigenvalues with the multiple multipole program – to compute these diagrams automatically, efficiently, and with a high accuracy. Finally, we validate the results for some well known test cases.
Author(s): J. Smajic, C. Hafner, D. Erni, Jasmin Smajic, Christian Hafner, Daniel Erni
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 186 KB

Title: Wireless Propagation in Non Line of Sight Urban Areas using Uniform Theory of Diffraction
Abstract: This paper describes a three-dimensional electromagnetic propagation model for signal power prediction in a non line of sight urban area located in Singapore. The model, which is implemented using the Ohio State NEC-BSC V4.2 basic scattering code and is based on ray theory and uniform theory of diffraction (UTD) takes into account first, second, and third order effects including triple reflections and diffractions. The simplified propagation model of Raffles Place, the central business district of Singapore, uses more than 360 geometrical structures and is compared with data measured at 937.6 MHz along a drive route at the site. The results from the propagation model produced reasonable agreement with the measurements showing that a simplified model using UTD can be used to simulate the gross features of electromagnetic scatter in an urban area. It is shown that use of penetrable dielectric building walls are also necessary for accurate prediction of radio wave propagation in urban areas under non line of sight conditions. It is also found that third order scattering effects can be dominant in non line of sight situations and may be necessary for accurate predictions.
Author(s): G. A. Ellis
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Impact of Some Discontinuities on the Convergence of Numerical Methods in Electromagnetics
Abstract: The effect of discontinuities at edges and at feed-points of antennas on numerical convergence rates is investigated. In the case of edges, higher order representations of the edge-mode, expressed with the aid of Hermite splines, are shown to provide improved convergence in both global and local measures. When using a magnetic frill to excite an antenna, it is shown that when the current representation allows for the "charge jump" across the frill, then convergence is accelerated. The use of both sub-domain and entire-domain functions is explored.
Author(s): M. M. Bibby
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 176 KB

Title: Reducing Electromagnetic Coupling in Shielded Enclosures using a Genetic Algorithm -- Finite-Difference Time-Domain Solver
Abstract: Comprehensive shielding in modern electronic equipment may lead to resonant behaviour within the equipment enclosure. This paper presents a method for optimising the placement of sources of electromagnetic (EM) energy and susceptors to this EM energy within an enclosed resonant cavity. The source and susceptor are placed on a dielectric slab within a perfectly conducting enclosure to reduce the level of EM coupling between the two. Optimisation is facilitated using a genetic algorithm coupled with a finite-difference time-domain solver. Results are presented for single objective optimisation and multi-objective optimisation cases.
Author(s): Russell Iain Macpherson, N J Ryan, R. I. Macpherson, N. J. Ryan
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: The Marvels of Electromagnetic Band Gap (EBG) Structures
Abstract: Artists and scientists alike have been fascinated by the existence of periodic structures in nature. When these structures interact with electromagnetic waves many unique features result. Observables are characteristics such as frequency stop-bands, pass-bands, and band-gaps. Various terminology have been used to classify these structures depending on the domain of the applications in filter designs, gratings, frequency selective surfaces (FSS), photonic crystals and band-gaps (PBG), etc. We prefer to classify them under the broad terminology of “Electromagnetic Band-gaps (EBG)”. Recently, many researchers have adopted this terminology. Broadly speaking, EBG structures are 3-D periodic objects that prevent the propagation of the electromagnetic waves in a specified band of frequency for all angles of arrival and for all polarization states of electromagnetic waves. In practice, however, it is very difficult to obtain such complete band-gap structures and partial band-gaps are achieved. Filters typically cover the scalar situation and single angle of arrival. FSS typically cover limited angles of arrival and respond differently to polarization states. PBG typically cover in-plane angles of arrival and also sensitive to polarization states. Surveying the literature, one finds that FSS terminology has been widely used in the microwave community while PBG terminology has been widely applied in the optical community. This overview paper presents a powerful computational engine utilizing Finite Difference Time Domain (FDTD) technique integrated with novel extrapolating algorithms to illustrate the marvels of EBG structures. The paper addresses structures such as (a) FSS structures, (b) PBG crystals, (c) smart surfaces for communication antenna applications, (d) surfaces with perfectly magnetic conducting properties (PMC), (e) creation of materials with negative permittivity and negative permeability, (f) surfaces with reduced edge diffraction effects and (g) reduction of mutual coupling among array antenna elements. Some representative applications of these structures are highlighted. In the last several years, there have been numerous published conference papers and journal articles dealing with the characterizations and applications of EBG structures. This paper is based on some of the results published by the author and his co-workers in the cited references. The reader is encouraged to perform detailed literature search to learn more about this area.
Author(s): Y. Rahmat-Samii
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 471 KB

Title: A Decompose-Solve-Recompose (DSR) Technique
Abstract: A novel spatial Decompose-Solve-Recompose (DSR) technique is demonstrated to be very attractive for analyzing uniform and non-uniform large phased array (LPA) antennas, because it can accurately account for array edge effects. A simple concurrent periodic/ non-periodic analysis scheme, similar to that utilized in the Progressive Numerical Method (PNM), is presented for the modeling of planar large phased array antennas. The resulting 2D spatial DSR technique, known as the Hybrid Edge-Periodic DSR technique, requires the decomposition of a large planar array into an outer edge “ring” array and a central periodic array block.
Author(s): K. Y. Sze, K. F. Sabet, D. Chun
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 280 KB

Title: A 2-PIN LOADED PATCH AS A MULTIBAND ANTENNA
Abstract:
Author(s): S. F. Mahmoud, A. F. Almutairi
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 148 KB

Title: ANTENNA DESIGN AND RADIATION PATTERN
Abstract: Characteristics and radiation patterns of many antenna geometries and antenna arrays can be evaluated but not easily visualized. This paper presents a software package that has been developed to allow for 2D and 3D visualization of the radiation patterns for many different types of antennas and antenna arrays. The package allows the user to visualize the field patterns for a given type of antenna, and to display the constituent parameters (input impedance, directivity, gain, etc). The user may inspect the field pattern for a single element of many different types of antennas (such as dipole, loop, aperture) or for arrays of common elements. The parameters for these antennas or arrays may be varied manually or via an automated swept parameter menu. The program allows for the design and study of diverse antenna arrays. Common types of 1-D, 2-D, and 3-D arrays are available, as well as a builder for an arbitrary system of elements. Synthesis and simulation tools are also integrated into the package to allow for automatically determining the best configuration for an array or an element to meet a predetermined radiation characteristic.
Author(s): A. Z. Elsherbeni, M. J. Inman, R. C. L. Riley
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 421 KB

Title: Aperture-Coupled Stripline-to-Waveguide
Abstract: A full-wave electromagnetic model is developed and verified for a waveguide transition consisting of slotted rectangular waveguides coupled to a strip line. This waveguide-based structure represents a portion of the planar spatial power combining amplifier array. The electromagnetic simulator is developed to analyze the stripline-to-slot transitions operating in a waveguidebased environment in the X-band. The simulator is based on the method of moments (MoM) discretization of the coupled system of integral equations with the piecewise sinusodial testing and basis functions in the electric and magnetic surface current density expansions. Electric and magnetic dyadic Green’s functions used in this integral equation formulation are developed for an infinite rectangular waveguide in the form of partial expansion over the complete system of eigenfunctions of a transverse Laplacian operator. Numerical results are obtained and compared with a commercial microwave simulator for a few representative structures, including various configurations and planar arrays of slotted waveguide modules coupled to a strip line.
Author(s): C. W. Hicks, A. B. Yakovlev, M. B. Steer
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 199 KB

Title: ACCURACY OF THREE UNCONDITIONALLY-STABLE FDTD SCHEMES
Abstract: This paper discusses accuracy limitations due to numerical dispersion and time step size for three implicit unconditionally-stable FDTD methods: Alternate-Direction-Implicit (ADI), Crank-Nicolson (CN) and Crank-Nicolson-Douglas-Gunn (CNDG). It is shown that for a uniform mesh, the three methods have the same numerical phase velocity along the axes, but have large differences along the diagonals. The ADI method has two orders-of-magnitude larger anisotropy than that of CN and CNDG. CNDG has no anisotropy at certain Courant numbers and mesh densities. At the limit of zero spatial mesh size, the three methods have different “intrinsic temporal dispersion” for a given time step size: CN has no anisotropy; ADI has positive anisotropy and CNDG has negative anisotropy, which is much smaller than ADI. The Nyquist sampling theorem provides a fundamental upper bound on the time step size for all three methods. It is shown that for ADI and CN the practical upper bound is close to the Nyquist limit, but for CNDG is half the Nyquist limit.
Author(s): G. Sun, C. W. Trueman
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: Accelerating Computations with a MoM-Based Computer Program
Abstract: Electromagnetic research often requires studies within wider frequency ranges. For achieving a fine resolution in the frequency domain, the required computation time is usually high. Here the MoM-based field computation program FEKO working in frequency domain is used for this purpose. In order to reduce the computational costs by minimizing the number of sampling points used, the interpolation algorithm MPBE (Model Based Parameter Estimation) is applied to achieve a mathematically based approximation of the problem. This paper presents the acceleration of computations with FEKO using the interpolation algorithm MBPE. A short introduction to FEKO is given at the beginning. Subsequently the implementation of MBPE as well as three possible adaptive strategies for further shortening the computation time is presented. Finally examples are given that show the advantages of this implemented method.
Author(s): M. Schick, F. M. Landstorfer
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 878 KB

Title: Analysis of Scattering Problems by MOM
Abstract: In this paper a method for the solution of scattering problems is proposed. In particular the EFIE is solved by a collocation point procedure, where the unknown current density is expanded by Daubechies wavelets on the interval and the integration is performed in the wavelet domain by the integral operator, hence without the use of any quadrature formula. Comparison with induced currents calculated by a standard MoM and with fields calculated by a FEM code are reported.
Author(s): S. Barmada, M. Raugi
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 182 KB

Title: On the Construction and Use of Two-Dimensional Wavelet-Like Basis
Abstract: An alternative method for generating higher dimensional wavelet-like basis functions is proposed in this paper. One method that has been used was to derive the two-dimensional wavelet-like basis from the two-dimensional traditional finite element basis. However, in this paper, products of one-dimensional wavelet-like functions are used as two-dimensional waveletlike basis functions. The generation of linear wavelet-like functions is discussed in detail and the use of linear and higher order wavelet-like functions is also investigated. The advantages and disadvantages of this technique for deriving wavelet-like basis functions will be discussed.
Author(s): W. E. Hutchcraft, R. K. Gordon
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 286 KB

Title: Multimode Hybrid Junctions
Abstract: The design, construction and testing of new hybrid junctions to perform the usual functions of summation and subtraction of incoming signals, not only over the fundamental mode but also to include the first few higher order modes, are important tasks for both military and civilian applications. The performance of the proposed junctions is evaluated experimentally and their relevance for a variety of microwave measurements and tracking radars suggested.
Author(s): M. Hamid
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 122 KB

Title: Electromagnetic Scattering by a System of Dielectric Spheres Coated With a Dielectric Shell
Abstract: Analytical solution is derived to the problem of scattering of electromagnetic plane wave by an array of dielectric spheres each coated with a dielectric shell. The incident, scattered and transmitted electric and magnetic fields are expressed in terms of the vector spherical wave functions. The vector spherical translation addition theorem is applied to impose the boundary conditions on the surface of various layers. Numerical results are computed and presented graphically for the radar cross sections of several configurations of spheres system with multi dielectric layers.
Author(s): A-K. Hamid, M. I. Hussein, M. Hamid
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
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Title: A Fast Forward Model for Simulating EMI Scattering with Realistic Sensors and Elongated Objects
Abstract: Fast solutions for UWB electromagnetic induction (EMI) scattering from fundamental object shapes are of longstanding interest for sensing of metallic objects, e.g. underground unexploded ordnance (UXO) detection and discrimination. Researchers have recently developed the general formulation for an analytical solution for EMI scattering from a spheroid. The specialization based on Small Penetration Assumption (SPA) is designed to attack the high frequency difficulties that challenge many numerical techniques. This paper uses the new analytical techniques to explore scattering from spheroids and other objects, with excitation complicated by non-uniform fields. To perform the necessary decomposition of the transmitted primary field into spheroidal modes, we represent the transmitter by a set of magnetic dipoles, which dramatically increases efficiency. The performance of the SPA solution is evaluated by comparison with results from other numerical techniques and measured data. Comparison with measured data also indicates that EMI signals from some complicated objects can be approximated by those from spheroids with similar proportions, which is promising for applications requiring fast solutions, such as inversion processing.
Author(s): K. Sun, K O’Neill, I. Shamatava, F. Shubitidze, K. D. Paulsen
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 450 KB

Title: Computation of SAR in Cell Culture Flasks Exposed to 900 MHz GSM Type Signals in a Modified TEM Cell
Abstract: In order to provide rigorous dosimetry for in vitro studies, Telstra Research Laboratories has developed a modified transverse electromagnetic cell exposure system. The system acts as a chamber for experiments in which a human cell culture exists as a very thin monolayer adhered to the bottom of a plastic culture flask under a layer of several millimetres of RPMI nutrient medium while incubated in a controlled atmosphere. A key to the rigour of any experiment seeking to investigate possible effects of electromagnetic energy on living systems is to ensure that the exposures used are accurately known, and to achieve this, numerical methods for the challenging task of characterising the SAR profile in the medium have been developed. This paper describes salient aspects of the development and analysis of the system.
Author(s): R. L. McIntosh, R. J. McKenzie, S. Iskra, A. Carratelli, P. Standaert
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 238 KB

Title: Performance of Preconditioned Krylov Iterative Methods for Solving Hybrid Integral Equations in Electromagnetics
Abstract: In Solving systems of linear equations arising from practical engineering models such as the eletromagnetic wave scattering problems, it is critical to choose a fast and robust solver. Due to the large scale of those problems, preconditioned Krylov iterative methods are most suitable. The Krylov iterative methods require the computation of matrix-vector product operations at each iteration, which account for the major computational cost of this class of methods. We use the multilevel fast multipole algorithm (MLFMA) to reduce the computational complexity of the matrix-vector operations. we conduct an experimental study on the behavior of three Krylov iterative methods, BiCG, BiCGSTAB, and TFQMR, and two preconditioners, the ILUT preconditioner, and the sparse approximate inverse (SAI) preconditoner. The preconditioners are constructed by using the near part matrix numerically generated in the MLFMA. Out experimental results indicate that a well chosen preconditioned Krylov iterative method maintains the computational complexity of the MLFMA and effectively reduces the overall simulation time.
Author(s): J. Lee, J. Zhang, C. Lu
File Type: Journal Paper
Issue:Volume: 18      Number: 3      Year: 2003
Download Link:Click here to download PDF     File Size: 608 KB