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Title: Electromagnetics Computations Using the MPI Parallel Implementation of the Steepest Descent Fast Multipole Method (SDFMM).
Abstract: The computational solution of large-scale linear systems of equations necessitates the use of fast algorithms, but is also greatly enhanced by employing parallelization tachniques. The objective of this work is to demonstrate the speedup achieved by the MPI-based parallel implementation of the Steepest Descent Fast Multipole Method (SDFMM). Although this algorithm has already been optimized to take advantage of the structure of the physics of scattering problems, there is still the opportunity to speed up the calculation by dividing component tasks into pieces and using multiple processors to solve them in parallel. The SDFMM has three bottlenecks ordered as (1) filling the sparse impedance matrix associated with the near field moment method interactions, (2) the matrix vector multiplications associated with this sparse matrix (3) the far field interactions associated with the fast multipole method. The parallel implementation task is accomplished basically using a thirty-one node Intel Pentium Beowulf cluster and is also validated on a 4-processor Alpha workstation. The Beowulf cluster consists of thirty-one nodes of 350MHz Intel Pentium IIs with 256 MB of RAM and one node of a 4x450MHz Intel Pentium II Xeon shared memory processor with 2GB of RAM with all nodes connected to a 100 BaseTX Ethernet network. The Alpha workstation has a maximum of four 667MHz processors. The parallelized computer code is tested for different cases of the anti-personnel landmine detection application. Our numerical results show linear speedup in filling the sparse impedance matrix that tremendously reduced the overall code’s runtime. Using the 32-processors on the Beowulf cluster lead to achieve a 7.2 overall speedup and significant reduction in the runtime is gained using the 4-processors on the Alpha workstation.
Author(s): Magda El-Shenawee, Carey Rappaport, Desheng Jiang, Waleed Melsei
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 427 KB

Title: Electric Dyadic Green's Functions for Modeling Resonance and Coupling Effects in Waveguide-Based Aperture-Coupled Patch Arrays
Abstract: An efficient technique for the rapid development of electric Green's dyadics of a transversely layered, terminated rectangular waveguide is presented with application to waveguide-based aperture-coupled patch arrays. This technique uses a partial eigenfunction expansion resulting in a Sturm-Liouville problem for one-dimensional characteristic Green's functions in the waveguiding direction. In this representation, the one-dimensional characteristic Green's functions provide physical insight into resonance and surface wave effects occurring in overmoded layered waveguide transitions. Particularly, this is related to the correlation between transverse resonances in the waveguide cross-section and surface waves associated with a grounded dielectric slab waveguide. This is demonstrated for the examples of aperture-coupled patch arrays in the N-port waveguide transition, although the analysis is applicable to other waveguide-based antenna structures, which allow for the propagation of surface waves.
Author(s): Alexander B. Yakovlev, Sean Ortiz, Mete Ozkar, Amir Mortazawi, Michael B. Steer
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 234 KB

Title: Three-Dimensional Geometrical Optics Code for Indoor Propagation
Abstract: This paper presents program GO_3D for computing the fields of a transmitter in an indoor environment using geometrical optics. The program uses an “image tree” data structure to construct the images needed to compute all the rays carrying fields above a preset “threshold” value, no matter how many reflections are needed. The paper briefly describes the input file required to define wall construction, the floor plan, the transmitter, and the receiver locations. A case study consisting of a long corridor with a small room on one side is used to demonstrate the features of the GO_3D program.
Author(s): C.W. Trueman
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 733 KB

Title: Modeling of Planar Multilayered Periodic Arrays using the Method of Lines
Abstract: This paper presents an implementation of the Method of Lines, a semi-analytical method, for the numerical modeling of radiating stratified periodic structures composed of dielectric layers interspersed with metallic patches and slots. Beam scanning antenna arrays and frequency selective surfaces (FSS) are among possible applications. The combined use of the Modified Bioconjuguate Gradient Squared method with Stabilization, an interactive resolution method, together with the Fast Fourier Transform allows for the analysis of a wide array of problems using uniform, high discretization density by considerably speeding up the resolution process and drastically reducing memory requirements. Periodic FSS and slot coupled patch array antennas were simulated. A comparison of simulation results with available literature allows validation of the new approach.
Author(s): Aric Choiniere, Jean-Jacques Laurin
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 1387 KB

Title: TRANSMISSION AND REFLECTION CHARACTERISTICS OF A CLASS OF MODIFIED COPLANAR WAVEGUIDE STRUCTURES
Abstract: In this paper, several geometries of a class of grounded coplanar waveguide (GCPW) are investigated using the finite difference time domain (FDTD) method, and their losses are computed. A uniform grounded coplanar waveguide (GCPW) structure is used as a reference case for the other non-uniform geometries. First, this reference case is studied. For this case, four geometries are proposed to study the transmission and loss effect of replacing parts of the dielectric substrate with free space. Afterwards, two new geometries are simulated to study the effect of introducing a neck and a gap in the microstrip feeding line, with and without a bridge that connects the two parts of the microstrip feeding line separated with the gap. The effect of adding a PEC cap above the microstrip feeding line, and connecting the two side ground planes, is also studied. The conductor attenuation is studied for the basic GCPW geometry. The power losses are also calculated for the uniform geometries. The line impedance is calculated for all geometries at several points.
Author(s): Abdelnasser. A. Eldek, Atef. Z. Elsherbeni, Charles. E. Smith
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 378 KB

Title: Limits for Computational Electromagnetics Codes Imposed by Computer Architecture
Abstract: The algorithmic complexity of the innermost loops that determine the complexity of algorithms in computational electromagnetics (CEM) codes are analyzed according to their operation count and the impact of an underlying computer hardware. As memory chips are much slower than arithmetic processors, codes that involve a high data movement compared to the number of arithmetic operations are executed comparatively slower. Hence, matrix-matrix multiplications are much faster than matrix-vector multiplications. It is seen that it is not su•cient to compare only the complexity, but also the actual performance of algorithms to judge on faster execution. Implications involve FDTD loops, LU factorizations and iterative solvers for dense matrices. Run times on two reference platforms, namely an Athlon 900 MHz and an HP PA 8600 processor, verify the •ndings.
Author(s): Juergen v.Hagen, Werner Wiesbeck
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 2879 KB

Title: Propagation of Electromagnetic Waves in a Rectangular Tunnel
Abstract: A study of radio communication in the underground metero tunnel of the city of Cairo, Egypt was carried out. A part of this tunnel was selected, which has a rectangular shape. Its dimensions are 8.85 m. wide, 5.9 m. height and 4.5 km. long. The walls are made of concrete which have conductivity between 10^-1 to 10^-2 mho/m. The attenuation below and above the cutoff frequency, both for the two values of σ are accounted for and graphically drawn. The results are plotted versus selected frequencies ranging between 30-300 MHz show the attenuation for TEmn and TMmn (m,n=0,1) modes. It is found that the attenuation constant for 30 MHz is smaller than for 300 MHz.
Author(s): Osama M. Abo Seida
File Type: Journal Paper
Issue:Volume: 17      Number: 2      Year: 2002
Download Link:Click here to download PDF     File Size: 224 KB