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Title: September 2008 Full Journal
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 11657 KB

Title: September 2008 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 169 KB

Title: New Stability Criterion for Unstructured Mesh Upwinding FVTD Schemes for Maxwell’s Equations
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 240 KB

Title: A Review of Perfectly Matched Absorbers for the Finite-Volume Time-Domain Method
Abstract: Different implementations of planar perfectly matched absorbers are studied under the unified framework of the Finite-Volume Time-Domain (FVTD) method. This comparative analysis allows to discuss the similarities existing between the theoretical models and explores the differences in their practical implementation and numerical performance in the framework of the FVTD method. Numerical experiments for performance analysis of the different PML models are conducted in terms of discretization and angle of incidence using waveguide models. The results are compared to theoretically expected values and to the first-order Silver M¨uller absorbing boundary condition.
Author(s): T. Kaufmann, K. Sankaran, C. Fumeaux, R. Vahldieck
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 318 KB

Title: A General Framework for Mixed Structured/Unstructured PEEC Modelling
Abstract: The paper proposes a re-formulation of PEEC modeling in terms of dual discretization of surface conductors. The result is a precise formalization of the PEEC tessellation and gives the possibility of handling general meshes, both structured and unstructured. This fact allows the use of triangular meshes only where necessary, leaving orthogonal discretization whenever possible and improving computational performances. The method, referred to as dual-PEEC, is validated by solving a structure referenced in literature and finally applied to the computation of the input impedance of a spiral inductor.
Author(s): F. Freschi, M. Repetto
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 608 KB

Title: Preliminary Investigation of the NCP Parameter-Choice Method for Inverse Scattering Problems Using BIM: 2-D TM Case
Abstract: A new method of choosing the regularization parameter, originally developed for a general class of discrete ill-posed problems, is investigated for electromagnetic inverse scattering problems that are formulated using a penalty method. This so-called normalized cumulative periodogram (NCP) parameterchoice method uses more information available in the residual vector, as opposed to just its norm, and attempts to choose the largest regularization parameter that makes the residual resemble white noise. This is done by calculating the NCP of the residual for each choice of the regularization parameter, starting from large values and stopping at the first parameter which puts the NCP inside the Kolmogorov-Smirnov limits. The main advantage of this method, as compared, for example, to the L-curve and Generalized Cross-Validation (GCV) techniques, is that it is computationally inexpensive and therefore makes it an appropriate technique for large-scale problems arising in inverse imaging. In this paper, we apply this technique to the general-form Tikhonovregularized functional arising in the 2-D/TM inverse electromagnetic problem, which is formulated via an integral equation and solved using the Born Iterative Method (BIM).
Author(s): Puyan Mojabi, Joe LoVetri
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 1896 KB

Title: Finite Element Modeling of Dual-Core Photonic Crystal Fiber
Abstract: In this paper, coupling characteristics of dualcore photonic crystal fiber (PCF) are studied extensively using vector finite element method, which has the potential to realize wavelength selective MUX-DEMUX for wavelength division multiplexing (WDM) application. Dispersion characteristic is also reported and demonstrates the wavelength region where it can support short duration soliton like pulses.
Author(s): K. R. Khan, T. X. Wu
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 119 KB

Title: A Parallel Numerical Method to Solve High Frequency Ghost Obstacle Acoustic Scattering Problems
Abstract: A highly parallelizable numerical method for time dependent high frequency acoustic scattering problems involving realistic smart obstacles is proposed. A scatterer becomes smart when hit by an incoming wave reacts circulating on its boundary a pressure current to pursue a given goal. A pressure current is a quantity whose physical dimension is pressure divided by time. In particular in this paper we consider obstacles that when hit by an incoming acoustic wave try to generate a virtual image of themselves in a location in space different from their actual location. The virtual image of the obstacle (i.e.: the ghost obstacle) is seen outside a given set containing the obstacle and its virtual image in the apparent location. We call this problem ghost obstacle scattering problem. We model this acoustic scattering problem and several other acoustic scattering problems concerning other types of smart obstacles as optimal control problems for the wave equation. Using the Pontryagin maximum principle the first order optimality conditions associated to these control problems are formulated. The numerical method proposed to solve these optimality conditions is a variation of the operator expansion method and reduces the solution of the optimal control problem to the solution of a sequence of systems of integral equations. These systems of integral equations are solved using suitable wavelet bases to represent the unknowns, the data and the integral kernels. These wavelet bases are made of piecewise polynomial functions and have the property that the matrices that represent the integral operators on these wavelet bases can be approximated satisfactorily with very sparse matrices. This property of the wavelet bases makes possible to approximate the optimal control problems considered with linear systems of equations with hundreds of thousands or millions of unknowns and equations that can be stored and solved with affordable computing resources, that is it makes possible to solve satisfactorily problems with realistic obstacles hit by waves of small wavelength. We validate the method proposed solving some test problems, these problems are optimal control problems involving a “smart” simplified version of the NASA space shuttle hit by incoming waves with small wavelengths compared to its characteristic dimension. We consider test problems with ratio between the characteristic dimension of the obstacle and the wavelength of the time harmonic component of the incoming wave up to approximately sixty. The numerical results obtained are very satisfactory. The website: http://www.econ.univpm.it/recchioni/scattering/w16 contains stereographic and virtual reality applications showing some numerical experiments relative to the problems studied in this paper. A more general reference to the work in acoustic and electromagnetic scattering of the authors and of their coauthors is the website: http://www.econ.univpm.it/recchioni/scattering.
Author(s): L. Fatone, M. C. Recchioni, F. Zirilli
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 799 KB

Title: Analysis of a Singly-Fed Circularly Polarized Electromagnetically Coupled Patch Antenna
Abstract: This paper presents analysis of a broadband circularly polarized electromagnetically coupled patch antenna (EMCP) fed thorough a coaxial probe. The bandwidth of the antenna is investigated numerically and through experiment. The 12% bandwidth of the measured return loss implies broadband behavior considering the operating frequency and the inherent bandwidth limitations of the microstrip antenna structure. The changes in circular polarization bandwidth were investigated using finite-element-method (FEM) software and the results suggest that the increase in separation between the patches causes a decrease of 3dB bandwidth and the degradation of the minimum value of axial ratio. An axial ratio bandwidth of 2% is achieved in the reported EMCP structure. In addition, we have applied a modal analysis using finite-difference time-domain (FDTD) simulation to reveal the simultaneous excitation of TM01 and TM10 modes at around 1.3GHz. These results help explain the broadband and circular polarization characteristics of the EMCP structure under investigation.
Author(s): A. Hajiaboli, M. Popović
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 277 KB

Title: Stochastic Optimization of a Patch Antenna
Abstract: The paper describes an efficient technique for optimizing the shape of the patch of a multi-band antenna by means of Genetic Algorithms and the hybrid FEM– RBCI method, for the analysis of open-boundary scattering and radiation electromagnetic field problems. The admissible rectangular patch area is logically and regularly subdivided into rectangular sub-areas, coinciding with the trace of the tetrahedral edge element mesh on the patch surface. In this way the relevant matrices of the finite element algebraic system, computed at the beginning of the optimization, remain unchanged, even if the patch is changed by inserting some metallic sub-areas. Moreover, in order to reduce the computing time of the iterative solver, the solution of a similar patch configuration is used as the initial guess for the solver.
Author(s): S. Alfonzetti, G. Borzě, E. Dilettoso, N. Salerno
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 115 KB

Title: A New Broadband Microstrip Leaky – Wave Antenna
Abstract: This paper presents a novel design of a curve tapered leaky-wave antenna (LWA). An FDTD code was used to extract the propagation constant of a microstrip LWA and to run a simple algorithm to design its layout. A physical grounding structure along the length of the antenna allows the adoption of a simple feeding planar line and the reduction of sidelobes. Moreover, the proposed design of LWA has interesting performance both for its bandwidth, (up to 33% for VSWR< 2) and for its gain (more than 12 dBi peak power gain at 10.5 GHz), compared with conventional planar microstrip LWAs which work in the same frequency range but with narrower bandwidth (20% VSWR< 2) and peak power gain less than 10 dBi. A prototype of a LWA proposed, was made showing a good agreement between experimental and theoretical results.
Author(s): O. Losito
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 473 KB

Title: Two-Element T-Array for Cross-Polarized Breast Tumor Detection
Abstract: This paper reports on a computational study of a 2-element cross-polarized antenna array for breast cancer detection. The “Dark Eyes” antenna is used in a T-arrangement to form the array. The antenna return loss is below -10dB in the range 2.3-10.3 GHz and the cross-polarized mutual coupling is less than -30dB for frequencies over 2.4 GHz. Using the finite-difference time-domain (FDTD) method, an ultra-wideband (UWB) pulse is transmitted in the numerical breast phantom and the co- and cross-polarized back-scatter response is recorded from tumors at different locations. The breast phantom was modeled as a simple layered medium of skin and fat. The dispersive properties of layers were introduced through a Debye model. Simulation results for a spherical and a cylindrical tumor of different orientations are presented and discussed.
Author(s): H. Kanj, M. Popovic
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 3879 KB

Title: Finite Array Analysis Through Combination of Macro Basis Functions and Array Scanning Methods
Abstract: The Macro Basis Functions (MBF) approach receives increasing attention for the evaluation of the effects of array truncation. In this paper, we show how physically based MBFs can be obtained from solutions for infinite arrays and for arrays of minimal size. The method is first explained and illustrated for the case of finite-by-infinite arrays of electrically connected taperedslot antennas. It is then extended to the case of planar arrays. Very low error levels are achieved with a small number of MBFs, in terms of port currents as well as in terms of radiation patterns.
Author(s): C. Craeye, R. Sarkis
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 1291 KB

Title: Robust Adaptive Beamforming Using Least Mean Mixed Norm Algorithm
Abstract: This paper proposes an accurate and rapidlyconvergent algorithm for enhanced adaptive beamforming based on the combination of the least mean mixed norm (LMMN) algorithm with initialization using sample matrix inversion (SMI). The algorithm uses a mixing parameter  which controls the proportions of the error norms and offers an extra degree of freedom within the adaptation. Monte Carlo simulations show that the misadjustment curve has a minimum at  = 0:40 which means that the proposed algorithm has an optimum steady-state performance at this mixing parameter value. The convergence of the algorithm is further improved by employing SMI to initialize the weights vector in the LMMN update equation. This makes the proposed SMI-initialized LMMN algorithm have a better steady state performance when compared to the least mean squares (LMS) algorithm and better stability properties when compared to the least mean fourth (LMF) algorithm. Simulation results obtained show that the developed SMI-initialized LMMN algorithm outperforms other algorithms in terms of computational efficiency, numerical accuracy, and cosnvergence rate.
Author(s): R. M. Shubair, S. A. Jimaa, A. A. Omar
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 333 KB

Title: An Accurate Reduced-Order Polynomial Solution for Root-MUSIC Source Localization Using Displaced Sensor Arrays
Abstract: This paper proposes a modified Root-MUSIC direction finding algorithm for source localization using a displaced sensor array (DSA) configuration which utilizes two parallely-displaced arrays in the vertical plane. It is shown that the proposed configuration utilizes the spatial displacement of array sensors in both the horizontal and azimuth directions together with the symmetry of the two parallel arrays in order to reduce the rank of the spatial covariance matrix. This results in a reducedorder Root-MUSIC polynomial for which the complex roots correspond to the desired directions of the radiating sources to be localized. Simulation results show that the developed algorithm outperforms the standard Root- MUSIC algorithm for conventional uniform linear arrays (ULAs) in terms of computational efficiency, numerical accuracy, and angular resolution.
Author(s): R. M. Shubair
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 221 KB

Title: The Design of a TRL Calibration Kit for Microstrip and its use for Measurement and Modeling of Active and Passive RF Components
Abstract: Microstrip TRL standards for the Thru, Reflect, and Line are designed, fabricated and tested. A split fixture design is built which contains microstrip to coaxial transitions to aid in measuring non-coaxial devices. With this microstrip TRL calibration kit, accurate and repeatable calibrations over a broad frequency range will be verified. This kit is used to measure and model several components such as a capacitor, an inductor, a transistor, and a radio frequency identification tag. The TRL kit allows the reference planes to be set at the device under test and allows novel modeling of the device’s intrinsic and extrinsic parameters through optimization of a network to minimize the difference between S-Parameter measurements taken with the TRL kit and device under test and the proposed model.
Author(s): D. Elsherbeni, L. Jordan, E. Hutchcraft, D. Kajfez, R. K. Gordon
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 761 KB

Title: A Discrete Random Medium Model for Electromagnetic Wave Interactions with Sea Spray
Abstract: Understanding the electromagnetic interactions with sea spray is of interest for many applications such as satellite or terrestrial communications, remote sensing systems for surveillance and meteorology. The water droplets in spray are a key factor in the energy transfer between the atmosphere and the ocean, which can help the wind speed retrieval algorithms for the global climate models. Furthermore, the presence of these droplets along the propagation path interferes with both land-based and satellite based remote sensing of the ocean surface. This paper investigates the backscatter response from sea spray, which is modeled as a layer of water droplets over a rough ocean surface. The distorted Born approximation technique is used in conjunction with the analytical wave theory to compute backscattering from the medium.
Author(s): O. Kilic
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 351 KB

Title: Abstraction of Graphics Hardware Through The Use of Modern Interfaces to Increase Performance of Linear Algebra Routines
Abstract: General purpose computation on graphics processing units (GPGPU) is introduced through the application of modern interfaces that abstract graphics hardware. In order to provide an example of these techniques, implementation of an iterative matrix solving algorithm is detailed using two interfaces – Stanford's BrookGPU and Accelerator from Microsoft Research. Performance of the Accelerator implementation is then analyzed.
Author(s): M. Woolsey, W. E. Hutchcraft, R. K. Gordon
File Type: Journal Paper
Issue:Volume: 23      Number: 3      Year: 2008
Download Link:Click here to download PDF     File Size: 192 KB