ACES Publication Search





There are 14 search results for:



Title: ACES October 2009 Full Journal
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 4890 KB

Title: ACES October 2009 Front Back Matter
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 217 KB

Title: New Compact and Broadband Patch Antenna Configurations for Wireless Applications
Abstract: We present new compact patch antenna configurations with broadband capabilities for wireless applications. Analytical, simulation, and experimental work is performed on semi-circular and quarter-circular patch antennas with a shorting pin. The resonant frequencies and radiation fields of the dominant cavity modes of the shorted patch are derived. For the shorted semi-circular patch, the broadband operation is based on the efficient excitation of two staggered modes of the patch. It is shown that a relative bandwidth of 58% is achieved with a patch area that is only 13.6% of the central wavelength squared. The shorted quarter circular patch with the same radius as the half circular one provides a relative bandwidth of about 30%.
Author(s): A. F. Almutairi, N. A. Aljuhaishi, S. F. Mahmoud
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 341 KB

Title: Design and Optimization of Single, Dual, and Triple Band Transmission Line Matching Transformers for Frequency-Dependent Loads
Abstract: This paper presents a design method for matching a frequency- varying load to a lossless transmission line at N frequency points using N transmission line sections. The formulation is based on the ABCD matrix of a cascaded N-section transmission line, terminated by a complex load. The unknown characteristic impedances and lengths of the sections are found by imposing the matching condition at N frequencies. Analytical solution for the nonlinear equations is known for the N = 1 case only; for N > 1, analytical solution is difficult to obtain, and therefore, the highly efficient particle swarm optimization method is used to find the design the parameters after casting the design into an optimization problem. Different numerical examples are presented and discussed that illustrate the validity of the proposed design method.
Author(s): M. Khodier
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 727 KB

Title: Scan Angle Extension by Array with Pattern Reconfigurable Elements
Abstract: In this paper, a linear phased array with pattern reconfigurable elements is studied to perform a scan angle extension of the array. The developed array can scan its main beam from -70o to 70o in its scanning plane. Compared with the traditional microstrip phased array, the scanning angle is extended remarkably.
Author(s): S. Xiao, Y. Y. Bai, B. Z. Wang, S. Gao
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 568 KB

Title: Quantitative Analysis of Breast Skin for Tumor Detection Using Electromagnetic Waves
Abstract: This paper supplements the existing knowledge on the breast skinís effect on microwaves for tumor detection in the frequency range 4GHz - 7GHz. A realistic breast model is developed using data of an MRI scan of a physical breast. The breast fibro glandular content along with the tumorís size and location are considered. Numerical results indicate that the skin and tumor signatures could be on the same order of magnitude. This confirms the need to include the skin layer in breast models to minimize the potential of false alarms in tumor detection.
Author(s): D. A. Woten, M. El-Shenawee
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 240 KB

Title: High Reflector by One-dimensional Quasi-Periodic Thue-Morse Multilayered Band Gap Structure at Ultra High Frequency Band
Abstract: The quasi-periodic Thue-Morse (T-M) multilayered band gap structures are studied at ultra high frequency band (UHF) by using a theoretical model based on matrix method (MM) for any incidence simulator. It is demonstrated that reflection spectrum in this frequency domain cover a great part of UHF band which contains the Global System for Mobile communication (GSM) bands, where the propagation of electromagnetic waves is forbidden in this region for all incident angle and all polarisations. The study of a deformed stack which is constructed according to the quasi-periodic sequences so that the coordinates y of the deformed object was determined through the coordinates x of the Thue-Morse stack in accordance with the following rule y=xk+1, where k: the coefficient defining the deformation degree. Consequently, an omni-directional high reflector at UHF band covering the GSM band is established.
Author(s): Y. Trabelsi, N. Ben Ali, Y. Bouazzi, M. Kanzari
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 315 KB

Title: Simulation of Lightning Return Stroke Currents and Its Effect to Nearby Overhead Conductor
Abstract: A nearby lightning strike can induce significant currents in long horizontal and vertical conductors. Although the magnitude of the current in this case is much smaller than that encountered during a direct strike, the probability of occurrence and the frequency content are higher. In view of this, appropriate knowledge of the characteristics of such induced currents is relevant for the interpretation of recorded currents. Considering these, the present paper discusses a modeling procedure that permits simulation of lightning-induced voltages or currents on overhead lines due to nearby lightning strikes. The hypothesis of perfect conducting ground, generally adopted in studies on the subject, is discussed in order to better assess the validity of the simulation results. In this paper, a homogeneous non-perfect ground is also investigated for its influence on lightning-induced voltages. The procedure for analyses of the voltages induced on an overhead line by a nearby lightning return stroke with a striking point at unequal distances from the line terminations is presented. The analysis shows that lightning-induced voltages depend on the soil conductivity.
Author(s): M. O. Goni, E. Kaneko, A. Ametani
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 357 KB

Title: Dispersion Analysis of a Negative Group Velocity Medium with MATLAB
Abstract: The dispersive behavior of a waveguide loaded with a metamaterial slab is investigated by means of common mathematical tools demonstrating the existence of a superluminal propagation region. More specifically, MATLAB has been used to investigate the influence of the propagating pulse shape on the possibility to achieve a propagation characterized by a negative group delay. Results achieved in this way have also been validated by means of a Finite Difference Time Domain code.
Author(s): G. Monti, L. Tarricone
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 711 KB

Title: RCS Estimation of 3D Metallic Targets Using the Moment Method and Rao-Wilton-Glisson Basis Functions
Abstract: This work deals on the estimation of the radar cross section (RCS) of five three-dimensional conductive objects: the metallic sphere, NASA almond, single ogive, double ogive and conesphere, using the Moment Method. The Rao-Wilton-Glisson (RWG) basis functions were used to expand the surface current of targets inside the Electric Field Integral Equation (EFIE). Triangular domains of RWG basis functions were constructed using MATLAB tessellation capabilities and a MATLAB code was developed and run to solve the electromagnetic scattering problem. As a result five RCS graphs, one for each target, were obtained. The accuracy of the program was validated by comparing the obtained results with those reported in the Literature.
Author(s): G. K. Carvajal, D. J. Duque, A. J. Zozaya
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 474 KB

Title: A Fast Spectral Domain Solver for the Characterization of Larger Microwave Structures in Multilayered Environments
Abstract: A new kind of fast spectral domain method is presented for the solution of integral equations related to planar structures embedded in multilayered media. It is based on the well-known spectral domain Greenís function for multilayered media to construct a diagonalized translation operator on the Cartesian wavenumber plane to efficiently evaluate the matrix-vector multiplications during the iterative solution process. This allows fast integral equation solutions for arbitrary layer arrangements similar as with fast multipole methods (FMM) for structures in free space. The convergence properties of the involved spectral domain integrals related to the group interactions are drastically improved by different integration path deformation strategies combined with enhanced Legendre- Filon and Laguerre quadrature techniques. Together with the use of diakoptic preconditioners, only a small number of iterations are required with the pertinent Krylov subspace solvers, typically leading to a significantly higher computational performance than comparable commercial integral equation solvers.
Author(s): T. Vaupel
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 718 KB

Title: An Adaptive Approximate Inverse-Based Preconditioner Combined with the Fast Multipole Method for Solving Dense Linear Systems in Electromagnetic Scattering
Abstract: We discuss preconditioning strategies for solving large Electric Field Integral Equation systems. We consider several algebraic preconditioners for solving the dense linear system arising from the Galerkin discretization of the pertinent integral equation.We show that approximate inverse methods based on Frobenius-norm minimization techniques can be very effective to reduce the number of iterations of Krylov subspace solvers for this problem class. We describe the implementation of the preconditioner within the Fast Multipole Algorithm and we illustrate how to reduce the construction cost by using static pattern selection strategies. Finally, we present deflating techniques based on low-rank matrix updates to enhance the robustness of the approximate inverse on tough problems. Experiments are reported on the numerical behavior of the proposed method on a set of realistic industrial problems.
Author(s): B. Carpentieri
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 153 KB

Title: Fast and Accurate Cascaded Particle Swarm Gradient Optimization Method for Solving 2-D Inverse Scattering Problems
Abstract: In this paper, a fast and accurate technique for solving the inverse scattering problem of two-dimensional objects made of perfect conductor is proposed. In this technique which is called cascaded particle swarm gradient, the solving procedure is properly divided into two steps. In the first step, the position and the equivalent radius of the unknown objects is estimated while in the second step, the accurate shape function of the objects is determined. The former step is performed by a global optimizer namely particle swarm optimization (PSO) technique and the latter is carried out by the well-known gradient method. In this work, the forward scattering problem is solved by the equivalent source method. Several numerical examples are presented to examine the proposed algorithm especially in handling the challenging multi-object problems with concave shape functions in the presence of measurement errors. The results show that the proposed algorithm is about 75 times faster than a conventional PSO while yielding a higher accuracy.
Author(s): M. Farmahini-Farahani, R. Faraji-Dana, M. Shahabadi
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 297 KB

Title: Layer-Based Integration Arithmetic of Conformal PML
Abstract: As an efficient artificial truncating boundary condition, conformal perfectly matched layer (CPML) is a multilayer anisotropic absorbing media domain. The conventional finite element analysis of CPML generates a large scale coefficient matrix that leads to prohibitive cost to solve. This paper proposes layer-based integration arithmetic, in which, the CPML multilayer integration is substituted by layer-wise summing of monolayer integration on the normal direction, with considering relative dielectric constant and permeability as constants in each very thin monolayer. The arithmetic needs to divide CPML into through-thickness elements of multiple layers, while the coefficient matrix of each element is evaluated by the layer-based integration. Numerical experiments show that the layer-based integration arithmetic is reliable and CPML under this arithmetic becomes a high-efficiency absorbing boundary condition.
Author(s): Y. J. Zhang, Q. Sun
File Type: Journal Paper
Issue:Volume: 24      Number: 5      Year: 2009
Download Link:Click here to download PDF     File Size: 518 KB