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Title: ACES May 2011 Full Journal
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 5288 KB

Title: ACES May 2011 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 990 KB

Title: Surface Integral Equation Method for Scattering by DB Objects with Sharp Wedges
Abstract: A surface integral equation method is used to analyze time-harmonic electromagnetic scattering by arbitrarily shaped three-dimensional DB objects with sharp wedges. At the DB boundary surface, the electric and magnetic flux densities D and B normal to the surface are zero. The DB boundary conditions are enforced by expanding the unknown equivalent surface current densities with divergence-free loop basis functions. The equations are tested with Galerkin’s method. The integral equation method is applied to investige field behavior at sharp DB wedges and the results are compared with the quasistatic solution in order to determine the accuracy of numerical solution at the sharp DB wedges.
Author(s): J. Markkanen, P. Ylä-Oijala, A. Sihvola
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 773 KB

Title: Design of a Compact Circular Waveguide Antenna of Low Polarization Level using EBG Structures
Abstract: A new technique to improve the performance, in terms of bandwidth, gain and polarization purity, of conventional circular waveguide antennas using an electromagnetic band gap (EBG) structure is presented. The proposed antenna is composed by a circular waveguide and two layers with squared holes located over the waveguide aperture. The dimensions of the antenna have been obtained by means of an optimization process that uses a rigorous analysis tool. According to the results, a notable enhancement in polarization purity and gain is demonstrated when incorporating the second grid. The EBG antenna has the peak gain 14.36 dBi and the cross polarization level is lower than 40 dB within a wide bandwidth of 17%. A prototype has been fabricated and measured operating at 9.1GHz.
Author(s): J. Gómez, A. Tayebi, I. González, F. Cátedra
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 1032 KB

Title: An Alternative Multiresolution Basis in EFIE for Analysis of Low-Frequency Problems
Abstract: An alternative multiresolution (MR) basis is presented for the method-of-moments (MoM) solution of the electric-field integral equation (EFIE) for the analysis of low-frequency problems. The proposed MR basis functions can be treated as an extension of the traditional looptree basis function to hierarchical functions. Similar to the loop-tree basis, the MR basis functions are linear combinations of standard Rao- Wilton-Glisson (RWG) functions. Therefore, the MR algorithm can be easily applied to MoM codes with RWG basis. Since the MR basis is immune from the so-called low-frequency breakdown, the MR basis is especially suitable for the analysis of low-frequency problems. Compared with the previous MR basis, the present MR basis is easier to construct and comprehend, and the basischanging matrix is sparser. Physical interpretation and comparison are given for the previous and present MR bases. Numerical results demonstrate that the both the previous and present MR bases are efficient for 3D electromagnetic scattering problems at low frequencies.
Author(s): J. Ding, J. Zhu, R. Chen, Z. H. Fan, K. W. Leung
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 1016 KB

Title: Realistic Spatio-Temporal Channel Model for Broadband MIMO WLAN Systems Employing Uniform Circular Antenna Arrays
Abstract: The development of realistic spatially and temporally clustered channel models is a prerequisite to the creation of successful architectures of the future MIMO wireless communication systems. IEEE 802.11n channel models are designed for indoor wireless local area networks for bandwidths of up to 100 MHz, at frequencies of 2 and 5 GHz. The channel models comprise a set of 6 realistic profiles, labeled A to F, which cover the scenarios of flat fading, residential, residential/small office, typical office, large office, and large space. Each channel scenario is represented by distinct path loss model, multipath delay profile, number of clusters and taps with predefined values for angular and power parameters. These realistic models have been applied widely for MIMO systems utilizing only uniform linear array (ULA). In this paper, modifications to the standard IEEE 802.11n channel model are applied to include uniform circular array (UCA) geometries. Characteristics of spatial fading corrections and the eigenvales distribution of subchannels for UCA-MIMO systems are investigated. The effect of the azimuth orientation and line of sight component existence on the system capacity for both ULA and UCA arrays are studied. Also, the water filling power allocation scheme is investigated under different realistic conditions. Furthermore, the link performance of Vertical Bell Laboratories Layered Space Time (VBLAST) that employs UCA at the receiver front is presented by utilizing the developed channel model.
Author(s): M. A. Mangoud, Z. Mahdi
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 1058 KB

Title: Local Residual Error Estimators for the Method of Moments Solution of Electromagnetic Integral Equations
Abstract: Several methods for estimating the local (cell-by-cell) error associated with a method of moments solution of the electric field integral equation are investigated. Three different residual error estimators are used with a variety of prototype structures. The global error estimates show reasonable correlation with the actual current density errors, and all three local error estimators correctly identify the high-error regions. Utility of the proposed error estimators is presented through a simple h-refinement technique.
Author(s): U. Saeed, A. F. Peterson
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 838 KB

Title: An Adaptive Preconditioning Technique using Fuzzy Controller for Efficient Solution of Electric Field Integral Equations
Abstract: For efficiently solving large dense complex linear systems that arise in the electric field integral equation (EFIE) formulation of electromagnetic scattering problems, a new adaptive preconditioning technique using fuzzy controller (FC) is introduced and used in the context of the generalized minimal residual iterative method (GMRES) accelerated with the multilevel fast multipole method (MLFMM). The key idea is to control the choice of the preconditioner to be used in an iterative solver by using fuzzy controller. This approach allows the expert knowledge to be taken into account on the controller design and utilizes feedback to tune the cores of the fuzzy set. Numerical results show that the best preconditioner can be selected while maintaining low cost for adaptive procedures.
Author(s): Z. Liu, J. Chen, R. S. Chen
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 807 KB

Title: Augmented MLFMM for Analysis of Scattering from PEC Object with Fine Structures
Abstract: In this paper, a multilevel Green’s function interpolation method (MLGFIM) combined with multilevel fast multipole method (MLFMM) is presented for solving the electromagnetic scattering from the objects with fine structures. In the conventional MLFMM, the size of the finest cube must be larger than a definite value, which is typically 0.2 ?; it often generates a large number of unknowns in each finest cube especially for objects with fine structures. Accordingly, it requires a lot of memory to store the near-field impedance matrix in MLFMM. In order to decrease the memory requirement of the near-field matrix in the MLFMM, the MLGFIM is introduced to calculate the near-field interactions. The number of unknowns in each cube can be less than a required number regardless of the size of the cube in the MLGFIM. To further reduce the computational complexity, many recompressed techniques, such as the adaptive cross approximation (ACA), QR factorization, and singular value decomposition (SVD), are applied to compress the low rank Green’s function matrix for speeding up the matrix-vector multiplication. Numerical results are given to demonstrate the accuracy and efficiency of the proposed method.
Author(s): M. Chen, R. S. Chen, X. Q. Hu
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 852 KB

Title: Transient Analysis of Electromagnetic Scattering using Marching-on-in-Order Time-Domain Integral Equation Method with Curvilinear RWG Basis Functions
Abstract: In this paper, a modified marching-onin- order time-domain integral equation method is utilized to analyze transient electromagnetic scattering from arbitrarily shaped objects. The spatial and temporal testing procedures are separate, and both of them are performed with the Galerkin’s method. The curvilinear RWG basis functions are used as spatial basis functions with curved triangular patch modeling. It gives a remarkable reduction to the number of unknowns, also the memory requirement and CPU time, without sacrificing the accuracy. The use of the weighted Laguerre polynomials as temporal basis functions ensures an absolutely stable solution even in late time. Several numerical results, including the single ogive and NASA almond, are given to demonstrate the accuracy and efficiency of the proposed method.
Author(s): Q. Q. Wang, C. Yan, Y. F. Shi, D. Z. Wang, R. S. Chen
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 989 KB

Title: Advanced Image Processing Techniques for the Discrimination of Buried Objects
Abstract: A numerical study for the electromagnetic detection of buried objects is presented. The whole GPR set-up is simulated through an integral formulation solved by means of the Method of Moments and a new discrimination process based on the 2D-Wavelet decomposition of computed electric field maps is proposed. The new wavelet methodology proves to be an effective tool for discrimination even in presence of noise.
Author(s): R. Araneo, S. Barmada
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 1261 KB

Title: Design of a Half-Mode SIW High-Pass Filter
Abstract: A planar high-pass filter with simple topology, low insertion loss and high power handling is presented in this paper. It is based on the half-mode substrate-integrated waveguide (SIW) structure whose shorting wall is implemented with periodical via-holes. Meanwhile, bevel edges are embedded to achieve good impedance matching. Parameter studies are also performed to give design insights for practical applications. A planar waveguide filter with cutoff frequency of 10 GHz is designed and built. The measured data have a good agreement with the simulated responses, and demonstrate practical utility of the proposed topology.
Author(s): W. Shao, J. L. Li
File Type: Journal Paper
Issue:Volume: 26      Number: 5      Year: 2011
Download Link:Click here to download PDF     File Size: 1308 KB