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Title: ACES May 2010 Full Journal
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 8935 KB

Title: ACES May 2010 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 384 KB

Title: Effect of Numerical Dispersion in FDTD Simulations of Light Scattering from Photoreceptors
Abstract: Abstract: Recently, the FDTD method was used to investigate the optical functional response of retinal photoreceptors. Light scattering patterns of the cells were simulated under various hypothetical states to determine the physiological processes that are most likely responsible for the experimentally observed signals. An FDTD model of a photoreceptor cell spans several wavelengths, therefore, the numerical dispersion, inherent in FDTD algorithms, will introduce significant phase errors in the simulation results. These phase errors can lead to erroneous predictions, especially for narrow band light stimulus. Currently, the qualitative and quantitive effects of numerical dispersion on light scattering computations are still unknown. In this paper, an analysis of the numerical dispersion errors in the near and far scattered fields is performed. The analysis provides decision guidelines for selecting enough computational resources to obtain the light scattering patterns with acceptable margin of errors.
Author(s): S. S. Abdallah, A. Iolov, K. Bizheva, O. M. Ramahi
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 357 KB

Title: Efficient Techniques for Accelerating the Ray-Tracing for Computing the Multiple Bounce Scattering of Complex Bodies Modeled by Flat Facets
Abstract: Abstract: A new algorithm to accelerate the raytracing for computing the radar cross section (RCS) of complex targets is presented. The algorithm is based on a combination of the angular Z-buffer (AZB), the volumetric space partitioning (SVP) and the depth-limited search method. The algorithm is very useful for RCS computing techniques based on geometrical optics (GO) and physical optics (PO). The targets are represented geometrically by a collection of flat patches. The approach is extremely efficient for computations of the RCS of large and complex bodies modeled by a high number of flat surfaces taking into account ray paths with multiple bounces. Results for representative targets are shown.
Author(s): F. Cátedra, L. Lozano, I. González, E. García, M. Algar
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 847 KB

Title: Parallel Implementations of the PEEC Method
Abstract: Abstract: This paper presents the first parallel implementation of a partial element equivalent circuit (PEEC) based electromagnetic modelling code suitable for solving general electromagnetic problems. The parallelization is based on the GMM++ and ScaLAPACK packages which are cross-platform libraries available for major operating systems. The parallel PEEC solver has been tested on several high performance computer systems. Large structures containing over 250 000 unknown current and voltage basis functions were successfully analyzed for the first time with a general PEEC-solver. The numerical examples are of orthogonal type, studied both in the time and frequency domain, for which memory, performance, and speed-up results are presented.
Author(s): D. Daroui, J. Ekman
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 1068 KB

Title: Advances of Neural Network Modeling Methods for RF/Microwave Applications
Abstract: Abstract: This paper provides an overview of recent advances of neural network modeling techniques which are very useful for RF/microwave modeling and design. First, we review neural network inverse modeling method for fast microwave design. Conventionally, design parameters are obtained using optimization techniques by multiple evaluations of EM-based models, which take a long time. To avoid this problem, neural network inverse models are developed in a special way, such that they provide design parameters quickly for a given specification. The method is used to design complex waveguide dual mode filters and design parameters are obtained faster than the conventional EM-based technique while retaining comparable accuracy. We also review recurrent neural network (RNN) and dynamic neural network (DNN) methods. Both RNN and DNN structures have the dynamic modeling capabilities and can be trained to learn the analog nonlinear behaviors of the original microwave circuits from input-output dynamic signals. The trained neural networks become fast and accurate behavioral models that can be subsequently used in systemlevel simulation and design replacing the CPUintensive detailed representations. Examples of amplifier and mixer behavioral modeling using the neural-network-based approach are also presented.
Author(s): H. Kabir, Y. Cao, Q. Zhang
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 343 KB

Title: High-Frequency Analysis of Scattering from Complex Targets in Half Space
Abstract: The high-frequency method for solving the scattering from electrically large conductive targets in half space is presented in this paper. The high-frequency method is deduced by introducing the half-space Green’s function into the conventional method of physical optics, method of equivalent currents. Combined with the graphicalelectromagnetic computing method and ray tracing technique that account for shadowing and multiple scattering in half space, one may calculate the radar cross-section of a conductive target object in a half space. The numerical results show that this method is efficient and accurate.
Author(s): X. Li, Y. Xie, R. Yang, Y. Wang
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 1562 KB

Title: EM Scattering by a Lossy Dielectric-Coated Nihility Elliptic Cylinder
Abstract: The problem of electromagnetic wave scattering by a lossy dielectric coated nihility elliptic cylinder is analyzed by solving the analogous problem of scattering by two lossy dielectric layers elliptic cylinder using the method of separation of variables. The incident, scattered, and transmitted fields are expressed in terms of complex Mathieu functions. Numerical results are obtained for the scattered fields of lossy and lossless dielectric coated nihility circular and elliptic cylinders to show their effect on the backscattering widths.
Author(s): A-K. Hamid
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 357 KB

Title: FDTD Investigation on Electromagnetic Scattering from Two-Dimensional Layered Rough Surfaces
Abstract: This paper presents an investigation into the electromagnetic scattering characteristic of two-dimensional (2-D) layered rough surfaces by using a finite-difference time-domain (FDTD) algorithm, which constitutes a three-dimensional scattering problem. The uniaxial perfectly matched layer medium is adopted for truncation of FDTD lattices, in which the finite-difference equations can be used for the total computation domain by properly choosing the uniaxial parameters. The upper and down rough surfaces are characterized with Gaussian statistics for the height and the autocorrelation function. The angular distribution of bistatic scattering coefficent from a 2-D singlelayered rough surface is calculated, and it shows good agreement with the numerical result through the Kirchhoff Approximation except for with large scattering angles. Finally, the bistatic scattering coefficents versus scattered and azimuthal angle for different conditions are analyzed in detail.
Author(s): J. Li, L. X. Guo, H. Zeng
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 1506 KB

Title: Electrical Performance Estimations for Shaped Dielectric Lens Antenna with Array Feed
Abstract: A shaped dielectric lens antenna with simple array feeds was developed to realize wide-angle beam scanning in car-mounted radar systems. The electrical performance of the dielectric lens antenna has been previously studied through electromagnetic simulations. The authors fabricated a practical dielectric lens antenna operating at 20 GHz and measured its performance. A convenient patch antenna configuration was developed for the array feed. A power divider comprising eight branched microstrip lines was designed in order to achieve precise excitation coefficients for the array feed. Design accuracy of the array feed was confirmed from measured and calculated results for the excitation coefficients and radiated electric field. To determine the wide-angle beam scanning characteristics, the aperture amplitude and phase distributions were estimated numerically using the obtained array radiated electric field. Excellent flat-phase characteristics were confirmed. The commercial electromagnetic simulator FEKO was employed for the numerical simulations. The radiation patterns at a 30° beam scanning angle were measured. Very good agreements between the measured and calculated results were found. Moreover, sufficient antenna gain was confirmed through experiments.
Author(s): Y. Tajima, S. Kamada, N. Michishita, Y. Yamada
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 3480 KB

Title: Calculation of the Magnetic Forces Between Planar Spiral Coils using Concentric Rings
Abstract: In this paper, the forces between current carrying planar spiral coils are calculated. In order to facilitate the calculation process, the coils have been replaced by concentric rings and using first and second order complete elliptic integrals, the forces between them have been calculated. The comparison of the calculations resulting from the replaced rings method and the direct method shows that the former is more effective in both simplicity and calculation time. To evaluate the precision of the calculations, planar spiral coils have been constructed and tested. The experimental results validate the results of the calculations.
Author(s): A. Shiri, A. Shoulaie
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 615 KB

Title: A New Method for Estimating the Direction-of-Arrival Waves by an Iterative Subspace-Based Method
Abstract: In this paper, a new subspace-based method for high-resolution direction-of-arrival (DOA) estimation of multiple plane waves in a noisy environment is proposed. This method called Iterative-Subspace-Decomposition (ISD) involves an iterative decomposition into two blocks of the matrices corresponding to the noise and the source subspaces. The proposed algorithm provides enhanced estimation performance of the DOA. It also significantly improves the resolution capability with respect to existing algorithms. The method can be applied to low signal-to-noise ratio (SNR) environment and is suitable for arrays with arbitrary sensor geometries, including linear arrays. Several numerical simulations are presented to assess the proposed method enhanced performance in comparison to that obtained by some classical algorithms. This comparative study has shown that the ISD leads to a significant reduction in the Root Mean Square Errors (RMSE) and resolution rate capabilities of the DOA estimates. As though, it is shown that the ISD method is superior in resolving closely spaced signals with a small number of snapshots and at low SNR.
Author(s): H. Changuel, A. Changuel, A. Gharsallah
File Type: Journal Paper
Issue:Volume: 25      Number: 5      Year: 2010
Download Link:Click here to download PDF     File Size: 428 KB