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Title: March 2007 Full Journal
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: March 2007 Matter and Index
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 442 KB

Title: A Perspective on the 40-Year History of FDTD Computational Electrodynamics
Abstract: This paper arises from an invited plenary talk by the author at the 2006 Applied Computational Electromagnetics Society Symposium in Miami, FL (The 71 original slides can be downloaded at http://www.ece.northwestern.edu/ecefaculty/ taflove/ACES_talk.pdf). This paper summarizes the author’s perspectives on the history and future prospects of finite-difference time-domain (FDTD) computational electrodynamics on the occasion of the fortieth anniversary of the publication of Kane Yee’s seminal Paper #1. During these four decades, advances in basic theory, software realizations, and computing technology have elevated FDTD techniques to the top rank of computational tools for engineers and scientists studying electrodynamic phenomena and systems.
Author(s): Allen Taflove
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Miniature Antennas and Arrays Embedded within Magnetic Photonic Crystals and Other Novel Materials
Abstract: Engineered materials, such as new composites, electromagnetic bandgap and periodic structures have been of strong interest in recent years due to their extraordinary and unique electromagnetic behaviors. This paper will address how modified materials, inductive/capacitive lumped loads and low loss magnetic materials/crystals are impacting antenna design with the goal of overcoming miniaturization challenges (viz. bandwidth and gain reduction, multi-functionality etc.). Dielectric design and texturing for impedance matching has, for example, led to significant size reduction and higher bandwidth low frequency antennas. Examples showing a factor of 2 or more reduction in ultrawideband antennas will be shown and operating down to nearly 100MHz using a 6” aperture. A recently introduced new class of magnetic photonic crystals (MPCs) and Degenerate Band Edge (DBE), displaying spectral nonreciprocity are also introduced. Studies of these crystals have demonstrated that MPCs exhibit the interesting phenomena of (a) drastic incoming wave slow down, coupled with (b) significant amplitude growth while (c) maintaining minimal reflection at the interface with free space. The phenomena are associated with diverging frozen modes that occur around the stationary inflection points within the band diagram. Taking advantage of the frozen mode phenomena, we demonstrate that individual antenna elements and linear or volumetric arrays embedded within the MPC and DBE structures allow for supergain effects that can lead to novel miniature (high sensitivity and high gain antennas and sensors) array configurations.
Author(s): John L. Volakis, Kubilay Sertel, Chi-Chih Chen
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Estimation of Blockage Effects of Complex Structures on the Performance of the Spacecraft Reflector Antennas by a Hybrid PO/NF-FF Method
Abstract: A hybrid (PO/NF-FF) method is presented in this paper for estimating the blockage effects of complex structures on the performance of the spacecraft mounted reflector antennas. The method estimates the blockage effect based on null-field hypothesis. The main advantage of this method is its ease of implementation for different obstacle geometries. The accuracy and functionality of the method is demonstrated by comparing the results of this method with other methods such as Method of Moments (MoM) and Direct (PO). An alternative definition of beam efficiency is adopted when the radiated power is available only in the forward radiation region. As a case study, the method is used to evaluate the effects of side panels on the performance of a reflector antenna operating at K band. A new parameter is also defined to represent the effects of absorbed power by panels. This parameter may be used to estimate the contribution of absorbed power in increasing system noise temperature.
Author(s): Keyvan Bahadori, Yahya Rahmat-Samii
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 585 KB

Title: Enhanced Functionality for Hardware-Based FDTD Accelerators
Abstract: In this paper we present several architectural enhancements to our previously published hardware-based FDTD acceleration platform. This includes the addition of several new sources, including H-polarized point sources, voltage and current sources, Gaussian beams, and user-defined sources, such as waveguide mode profiles. We also discuss the recent support for extending objects into the absorbing boundary, which minimizes non-physical back reflections. With the addition of these features, the FDTD acceleration hardware has become a more robust and powerful tool, enabling the rapid simulation of a wider breadth of applications, including antennas, waveguides, and optics.
Author(s): Petersen F. Curt, James P. Durbano, Michael R. Bodnar, Shouyuan Shi, Mark S. Mirotznik
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 1807 KB

Title: MoM Solution to Scattering from Three-Dimensional Inhomogeneous Magnetic and Dielectric Bodies
Abstract: This paper presents a method of moments solution to scattering problems that involve inhomogeneous magnetic and dielectric bodies of arbitrary shapes. The volume equivalence principle was used to switch from an original problem that deals with an inhomogeneous magnetic and dielectric scatterer to a problem in free space with equivalent sources. The problem is described through a mixed potential formulation. The method of moments technique is then applied to achieve a numerical solution to the original problem. The volume of the scatterer is meshed by tetrahedral cells and face-based functions are applied to expand unknown quantities. Special attention is paid to the curl operation on vector potentials and corresponding volume integrals. The proposed formulation has been evaluated through some examples.
Author(s): M. Hasanovic, C. Mei, J. R. Mautz, E. Arvas
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Surface Impedance Boundary Conditions of High Order of Approximation for the Finite Integration Technique
Abstract: Time domain Surface Impedance Boundary Conditions (SIBCs) of high order of approximation relating the electric field integral along the edge of the computational cell and the magnetic flux through its facet are derived and implemented into the Finite Integration Technique (FIT). It enables such effects as curvature of the conductor surface and variation of the electromagnetic field along the interface to be accurately described in the formulation. As a result, accuracy of numerical results is improved and the application area is expanded as compared with formulations employing classical low order Leontovich SIBCs. Numerical results obtained using low- and highorder FIT-SIBC formulations are compared with analytical results to demonstrate the advantages of the proposed approach.
Author(s): Luca Di Rienzo, Nathan Ida, Sergey Yuferev
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: An Adaptive Basis Function Solution to the 1D and 2D Inverse Scattering Problems using the DBIM and the BIM
Abstract: We present the use of an adaptive set of basis functions used in conjunction with the MoM to solve the linearized scalar inverse electromagnetic scattering problem. The basis functions, which are whole-domain and harmonic, are selected to provide a perfectly conditioned solution under the first-order Born approximation when multiple frequency experiments are considered. In order to iteratively solve the full nonlinear problem by the Distorted Born Iterative Method (DBIM) and/or the Born Iterative Method (BIM), we introduce a single parameter into the basis function expansion to demonstrate that it is possible to maintain a well-conditioned linearized inverse problem by selecting the parameter value that minimizes the condition number of the discrete matrix operator. The proposed technique eliminates the need for Tikhonov regularization or equivalent regularization schemes commonly applied to the single-frequency, pulse-basis formulation of the linearized inverse scattering problem.
Author(s): Ian Jeffrey, Vladimir I. Okhmatovski, Joe LoVetri, Colin Gilmore
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: High-Order FVTD on Unstructured Grids using an Object-Oriented Computational Engine
Abstract: An object-oriented implementation of a finite-volume time-domain (FVTD) engine for solving Maxwell’s equations is presented. The relevant aspects of the FVTD method are discussed from an objectoriented perspective and details of the object classes are given. Computational results obtained using the FVTD engine for solving Maxwell’s Equations on unstructured grids are also shown. The engine implements both MUSCL and polynomial interpolation methods to approximate the fluxes at the cell boundaries up to thirdorder accuracy. In addition, the engine has the capability of using a number of time-integration schemes. Results are presented for the transient scattering from a PEC sphere and a lossy dielectric cube. For the case of the sphere, almost perfect agreement with the analytic solution in the time-domain is achieved. The number of cells required as compared to FDTD is substantially reduced.
Author(s): Dmitry Firsov, Joe LoVetri, Ian Jeffrey, Vladimir Okhmatovski, Colin Gilmore Walid Chamma
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Improved Smart Antenna Design Using Displaced Sensor Array Configuration
Abstract: Abstract-In this paper we propose a new sensor array configuration for improved smart antenna design. The new configuration involves two parallely-displaced sensor arrays in the vertical plane. The proposed sensor array configuration avoids the problem of spatial aliasing encountered in largely spaced sensor arrays and reduces the effects of inter-element mutual coupling for closely spaced arrays. Moreover, the proposed sensor array configuration allows for doubling the number of array elements and, hence, increasing the system capacity, without significantly increasing the array aperture. This allows for a more accurate beam pattern to be generated especially in a radio environment with a large number of interference signals. Numerical results are presented to demonstrate the improved performance of direction-of-arrival estimation and adaptive beamforming algorithms when the proposed array configuration is used.
Author(s): Raed M. Shubair
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 190 KB

Title: Development of Wideband L-Probe Coupled Patch Antenna
Abstract: The patch antenna fed by an L-shaped probe was proposed in 1998. This feeding method, and its modified version, the meandering strip, has led to the development of a new class of wideband patch antennas which can be operated in linear, circular or dual polarization with excellent performance characteristics. L-probe coupled patch antennas are simple in structure and low in material and production costs. Moreover, it can be designed with dual wideband performance which is very attractive for modern mobile communications. This paper presents a review of the general designs for linearly and circularly polarized L-probe patch antennas. Comparisons between measured and simulated results are presented. Methods for gain enhancement and cross polarization suppression are also introduced. The designs and performances of two dual-band wideband L-probe fed patch antennas are also described.
Author(s): Kwai Man Luk, Kai Fong Lee, Hau Wah Lai
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 546 KB

Title: Novel Broadband Dielectric Resonator Antennas Fed Through Double-Bowtie-Slot Excitation Scheme
Abstract: This paper discusses the concept and the realization of novel wideband dielectric resonator antennas (DRAs), in which a dielectric cylinder or parallelepiped are fed from a microstrip line through two parallel bowtie-slots. The concept of partial independence of the slot modes from the dielectric resonator mode is exploited in such a way that the resonances of the slot modes and of the DRA are designed to occur at different frequencies. As a result, the bandwidth of the DRA is significantly improved, while stability in the radiation patterns and low cross-polarization are maintained. Finally, a study is performed concerning the influence of the gap between the dielectric resonator and the ground plane upon the overall performance of the DRA. Comparison of the results from a commercial software tool (HFSS®) and from the Finite-Volume Time-Domain (FVTD) method is made.
Author(s): G. Almpanis, C. Fumeaux, R. Vahldieck
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Approximated Method Neglecting Coupling for Conformal Array
Abstract: Full modeling of large conformal array can be time and memory consuming. An approximated method that takes into account the vectorial nature of the radiated field is presented. The radiation characteristic of the array is obtained by means of the vectorial sum of each element radiation characteristic, rotated according to the orientation of the element. The coupling between elements will be evaluated in the case of interest: a conformal array on an inflatable structure. In the approximated method, coupling will be neglected in such a case. To illustrate the approach, a spiral antenna will be chosen and modeled with MoM. Finally, array radiation patterns obtained by the approximated method will be compared with a full wave MoM to validate our
Author(s): François Chauvet, Régis Guinvarc’h, Marc Hélier
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 414 KB

Title: Two Element Phased Array Dipole Antenna
Abstract: Two element array of dipole antennas with 90 degree phase difference feed is proposed for directional antenna applications. In the numerical analysis, the electromagnetic simulator WIPL-D based on the method of moment is used. At first, the distance between the two elements is fixed to be a quarter wavelengths at the design frequency of 2.45 GHz. The front-to-back ratio is calculated. Then, by adjusting the length of the two elements and the distance between the two elements, a front-to-back ratio of 15.3 dB is obtained. The relation between the front-to-back ratio of this antenna and the feed point currents is discussed. The measured input impedance with 90 degree hybrid
Author(s): Mitsuo Taguchi, Kotaro Era, Kazumasa Tanaka
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 272 KB

Title: Mixed Order Tangential Vector Finite Elements (TVFEs) for Tetrahedra and Applications to Multi-Functional Automotive Antenna Design
Abstract: Mixed order tangential vector finite elements (TVFEs) of order 0.5, 1.5, and 2.5 for tetrahedra are presented and used in conjunction with an exact Finite Element-Boundary Integral (FE-BI) formulation. The main advantage of using mixed order elements is to reduce the computational complexity when solving large problems. As an illustrative example, a wide band antenna is designed and placed on an automobile. Results regarding the antenna return loss, far field pattern, axial ratio, and gain are presented.
Author(s): Tutku Karacolak, Erdem Topsakal
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 499 KB

Title: Modeling and Analysis of a Dual-Band Dual-Polarization Radiator Using FEKO
Abstract: A dual-band hybrid antenna element comprising of microstrip and waveguide radiating elements is theoretically investigated through computer simulations. The low band radiator is a Shorted Annular Ring (SAR) microstrip antenna and the high band antenna is an open ended circular waveguide. First, the characteristics of a SAR patch antenna are presented and reviewed. Then the dual-band antenna configuration is described, which is realized by forming a waveguide radiator in the shorted region of the SAR microstrip antenna. Modeling and analysis of the SAR patch antenna and the hybrid element are investigated using the method-of-moment-based software package FEKO. The analysis includes return loss computations showing the element bandwidth at different frequency bands and the radiation patterns in the E- and H- planes. Feeding the element in phase quadrature produces circular polarizations (CP). The radiation patterns of the CP dual-band element are also analyzed using FEKO and the axial ratio performance is subsequently assessed
Author(s): Amir I. Zaghloul, C. Babu Ravipati, M. T. Kawser
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 617 KB

Title: Polymorphic Time Domain Computational Electromagnetics
Abstract: CEM methods such as FDTD and TLM are the de-facto standard for general purpose EM field modeling in the time domain. On the other hand, the Microsoft .NET Framework and the associated C# programming language have become the de-facto standard for software development on Windows. This paper presents the technique for building a time domain CEM object library in C#. This approach could be the basis for creating an open-source standard CEM library.
Author(s): Poman P.M. So
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 356 KB

Title: Simulation of Non Linear Circuits by the Use of a State Variable Approach in the Wavelet Domain
Abstract: A method for the simulation of complex circuits with nonlinear elements is proposed. The method is based on wavelet expansion of the state variable description, and leads to a compact representation of the nonlinear problem which is characterized by accuracy and computational efficiency.
Author(s): S. Barmada, A. Musolino, M. Raugi
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 428 KB

Title: Monochromatic Scattering from Three-Dimensional Gyrotropic Bodies Using the TLM Method
Abstract: A three-dimensional scatter field Transmission Line Modeling (TLM) algorithm is established to obtain bistatic radar cross sections of gyroelectric and gyromagnetic objects at a single frequency.
Author(s): Ahmet F. Yagli, Jay K. Lee, Ercument Arvas
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 512 KB

Title: High Frequency Phase Variable Model of Electric Machines from Electromagnetic Field Computation
Abstract: This paper presents a high frequency phase variable model of electric machines obtained using finite element (FE) analysis. The model consists of the low frequency phase variable model in parallel with a high frequency winding branch. The resistance and inductance of individual winding turns are calculated by magnetodynamic FE analysis while capacitance is calculated by electrostatic FE analysis. With the obtained parameters, a distributed model was formed based on the winding arrangement. The order of the distributed winding model is reduced using the Kron reduction technique to form the lumped parameter high frequency winding branch. A Permanent Magnet synchronous motor (PMSM) with its operating inverter is used as an example. The developed model is then used to evaluate the motor-inverter interaction. The results show the ability of the developed model to represent the motor’s high frequency behavior under different operating conditions.
Author(s): O. A. Mohammed, S. Ganu, N. Abed, S. Liu, Z. Liu
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Cascading Optical Negative Index Metamaterials
Abstract: We use a spatial harmonic analysis (SHA) method to homogenize optical metamaterials with a negative refractive index; the method provides a more general approach than other methods for estimating the effective index of materials arranged of cascaded elementary layers. The approach is validated for a single layer and a triple layer two dimensional metal grating.
Author(s): Alexander V. Kildishev, Uday K. Chettiar
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
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Title: Characterizing Infrared Frequency Selective Surfaces on Dispersive Media
Abstract: With the emergence of frequency selective surfaces (FSS) and other passive planar antenna devices at infrared frequencies, the increasing need for accurate characterization using numerical modeling prior to device fabrication has exposed limitations in the traditional modeling procedures used for lower frequency FSS designs. To improve full-wave FSS models at IR, a procedure to measure and integrate dispersive material properties in modeling is described. Measured and modeled results are provided as verification demonstrating the need to account for material dispersion in infrared FSS design.
Author(s): James Ginn, Brian Lail, David Shelton, Jeffrey Tharp, William Folks and Glenn Boreman
File Type: Journal Paper
Issue:Volume: 22      Number: 1      Year: 2007
Download Link:Click here to download PDF     File Size: 509 KB