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Title: March 2008 Full Journal
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 7783 KB

Title: March 2008 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 220 KB

Title: An Improved Time-Domain Near-Field to Far-Field Transform in Two Dimensions
Abstract: Computing the far-field transient response of a two-dimensional geometry requires a convolution of near-field currents with a two-dimensional far-field impulse response. In this work, a purely time domain implementation is derived and its accuracy is demonstrated. This method is applicable to EMI, radiation, and scattering problems.
Author(s): J. A. Roden, S. L. Johns, J. Sacchini
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 200 KB

Title: Efficient Time-domain Sensitivity Analysis using Coarse Grids
Abstract: We propose an efficient coarse-grid approach to the sensitivity analysis with full-wave electromagnetic (EM) time-domain simulations. In order to compute the response sensitivity using an adjoint approach, waveforms at all perturbation grid points need to be saved and post-processed. Therefore, the memory requirements of the response sensitivity analysis may become excessive for electrically large objects or problems with a large number of optimizable parameters. The use of coarse grids can reduce these memory requirements drastically and improve the computational efficiency of the sensitivity analysis while maintaining good accuracy. In this paper, we show that the discretization step size used in the sensitivity computation can be many times larger than the step size used in the finite-difference timedomain (FDTD) simulation. The effects of the coarseness of the grid on the accuracy of the sensitivity analysis are investigated. Verification is carried out through 1-D, 2-D and 3-D lossy dielectric structures using commercial FDTD solvers.
Author(s): Y. Song, N. K. Nikolova, M. H. Bakr
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 363 KB

Title: Practical Implementation of a CPML Absorbing Boundary for GPU Accelerated FDTD Technique
Abstract: The use of graphical processing units (GPU) has been recently documented for the implementation of the FDTD technique; however, little has been reported about the necessary additions to three dimensional FDTD codes to make the technique more useful for fast antenna analysis and design. This paper details the addition of a convolutional perfectly matched layer absorbing boundary (CPML) to a three dimensional GPU accelerated FDTD code.
Author(s): M. J. Inman, A. Z. Elsherbeni, J. G. Maloney, B. N. Baker
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 1199 KB

Title: Broad-band Characterization of Wire Interconnects Using a Surface Integral Formulation with a Surface Effective Impedance
Abstract: A surface integral formulation is used for a broad-band characterization of wire interconnects. A suitable definition of effective impedance accounts for the penetration of currents and charges inside lossy conductors. The results are successfully compared to a volumetric integral approach.
Author(s): A. Maffucci, G. Rubinacci, S. Ventre, F. Villone, W. Zamboni
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 276 KB

Title: High-Frequency Full-Wave Analysis of Interconnects with Inhomogeneous Dielectrics through an Enhanced Transmission Line Model
Abstract: The paper deals with the inclusion of inhomogeneous dielectrics in a full-wave transmission line model for high-frequency analysis of interconnects. This “enhanced” transmission line model is derived from a full-wave integral formulation of the electromagnetic problem, and the inclusion of dielectrics is performed by an accurate semi-analytical evaluation of the Green functions for layered planar structures. The resulting model has a computational cost typical of a TL model but is able to perform a full-wave analysis in frequency ranges where the standard TL model may no longer be used. Moreover, as shown in the proposed examples, the model gives the possibility to investigate separately several phenomena affecting the high-frequency behavior of interconnects, like losses in dielectrics, unwanted radiation and excitation of parasitic modes.
Author(s): A. G. Chiariello, A. Maffucci, G. Miano, F. Villone, W. Zamboni
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 291 KB

Title: Circuit Models for Interconnects Using 3D Computational Techniques
Abstract: This paper presents a method to generate circuit models from 3D distributed structures. In the first step a broadband characterization of the device is obtained through a reduced order modeling technique. Then in the second step a rational approximation of the coefficients of the impedance matrix is derived using a root mean squared procedure. An equivalent circuit is then synthesized and allows a global circuit simulation of the whole structure. The proposed methodology can be used with a segmentation technique for the analysis of complex structures: a whole 3D structure can be subdivided into smaller parts. Each part is characterized by an equivalent circuit deduced from wideband analysis. The connection between the substructures makes available a global simulation of the whole system inside a circuit platform (SPICE for example). Numerical results are shown for different kinds of interconnects (tracks and cables).
Author(s): B. Essakhi, J. Benel, M. Smail, G. Akoun, L. Pichon
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 1025 KB

Title: Eddy Current Imaging of Surface Breaking Defects by Using Monotonicity Based Methods
Abstract: This paper is in the framework of the nondestructive evaluation of conductive materials by means of eddy current testing. In particular, we consider the imaging of surface breaking volumetric defects. In this case, it is possible to use relatively “high-frequencies” and, in the limit of skin-depth negligible with respect to the relevant geometrical sizes and negligible displacement current, the problem can be modeled as a magnetostatic one. The elliptic nature of magnetostatic allows proving a monotonicity property of the operator mapping the defects geometry into the measured quantity. This makes possible to use a recently proposed fast (noniterative) imaging algorithm.
Author(s): G. Rubinacci, A. Tamburrino , S. Ventre
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 1550 KB

Title: Design and Analysis of Partitioned Square Loop Antennas
Abstract: A novel antenna design is presented for operation at 5.8 GHz with omni-directional pattern characteristics. The antenna employs square loop geometry of one wavelength perimeter. The loop is partitioned with capacitive elements in order to minimize phase variations in the current flow and thereby enhance the radiation efficiency. Five capacitive elements are used to achieve optimal loop current flow, resulting in phase variations smaller than ± 6°. The performance of the antenna is first analyzed with a thin-wire antenna using method of moments (MoM) solver and later validated using a custom finite difference time domain (FDTD) package. The calculated radiation pattern in the plane of the loop is close to omni-directional with directive gain of 1.5 dBi. A printed circuit antenna is manufactured with alternating top- and bottom-layer conductors, with the overlapped regions acting as physical capacitors. The measured radiation patterns of the printed antenna confirm the predicted omni-directional behavior in the equatorial plane, while the input impedance demonstrates a close match to 50 Ω. The mean value of the gain is 2.15 dB at 5.869 GHz. A second printed antenna, having toplayer conductors only and gap capacitors, is simulated using finite element (FEM) software, and the performance is nearly omni-directional with a directive gain of 1.66 dBi. Both designs are very sensitive to the dimensions of the physical capacitors and require a highly accurate method of fabrication.
Author(s): R. Hasse, V. Demir, W. Hunsicker, D. Kajfez, A. Elsherbeni
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 457 KB

Title: Interval-Based Robust Design of a Microwave Power Transistor
Abstract: An interval-based approach aimed at the robust design of a specific performance of a Double Hetero-junction Bipolar Transistor (DHBT) for microwaves applications is presented. The robust design is obtained by looking at the range of the performance function by means of an overestimation, given in analytical form, of its amplitude. The proposed approach is described by referring to two theoretical performance functions to show the reliability for both the univariate and multivariate cases. The worst case approach is considered in order to study the minimum variation of the max oscillation frequency of the DHBT, obtained by a regression model from numerical results, in presence of given parameters variations. The physical and geometrical parameters affecting the performance are regarded as implicitly uncorrelated and uniformly distributed in an assigned range and therefore all their combinations are kept into account. The implemented approach permits to achieve a greater robustness of the solution without assuming approach-specific settings and additional computations dependent on designer’s ability and can be used to maximize the production yield.
Author(s): P. Lamberti, V. Tucci
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 1436 KB

Title: 7 Tesla MRI with RF Power and Field Homogeneity Comparable to 4 Tesla using Computational Electromagnetics
Abstract: In ultrahigh (≥ 7 Tesla) field magnetic resonance imaging (MRI), the electromagnetic interactions between the coil, its excitation sources, and the biological load become more significant compared to low MRI applications. Computational electromagnetic (CEM) techniques are currently playing a major role in the evaluation of MRI radiofrequency (RF) coils (commonly now, within ultrahigh field context, referred to as transmit arrays). This work compares the RF power requirements in 4 and 7 Tesla human MRI using CEM. Furthermore, we demonstrate that at ultrahigh MRI, highquality/ homogenous RF excitation fields could be obtained simultaneously with total RF power deposition lower than that achieved at lower field strengths. These results dispel what has been widely accepted from quasistatic approximations, namely that pushing the envelope of MRI field strength results in more RF power requirements and therefore, more RF power absorption in human tissue. This study is presented using the finite difference time domain (FDTD) method and a gradient based optimization method.
Author(s): L. Tang, T. S. Ibrahim
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 526 KB

Title: On-Wafer Measurement and Modeling of Silicon Carbide MESFET’s
Abstract: The goal of this work was to characterize Silicon Carbide (SiC) transistor devices, with measurements and modeling using an advanced software package. To characterize and model the SiC Metal- Semiconductor Field-Effect Transistors (MESFETs), onwafer measurements of the transistors were performed and their behavior was characterized. The transistors were measured using a vector network analyzer in conjunction with a probing station to make contact with the individual devices on the wafers. Once measurements were complete and typical performance characteristics found, equivalent circuit models were designed and the components optimized to create equivalent circuits with matching characteristics.
Author(s): L. Jordan, D. Elsherbeni, E. Hutchcraft, R. K. Gordon, D. Kajfez
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 323 KB

Title: Extracting the Electrical Properties of Polymeric Composite Materials through Circuit Simulation and Optimization
Abstract: The electrical properties of polymeric composite materials were extracted from measured data using optimization techniques in Advanced Design System (ADS), a circuit simulation tool. A vector network analyzer was used to measure the S-parameters of the composite materials. The materials were inserted in an X-band waveguide and measured from 8 GHz to 13 GHz. The measured data was used to reconstruct the relative permittivity and loss tangent against a modeled setup in ADS. Two techniques were implemented in the reconstruction of the permittivity, one with the permittivity and loss tangent assumed to be constant and the other with them considered to be a function of frequency. The results show that for both techniques the modeled data does converge to the measured data yielding an optimized permittivity and loss tangent.
Author(s): L. Bennett, W. E. Hutchcraft, R. K. Gordon, E. Lackey, J. G. Vaughan R. Averill
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 242 KB

Title: A Review of Statistical Methods for Comparing Two Data Sets
Abstract: Statistical approaches to compare data for validation of computational electromagnetics have been used for several years. They provide an accepted means of obtaining a numerical value to quantify the data under consideration. However, the use and meaning of these ‘numbers’ depends, by necessity, on the application. This paper provides an overview of some of the most widely applicable techniques, relating the output of these to visual assessment. It further includes comparison with the FSV (Feature Selective Validation) method allowing a triangulation between statistical approaches, visual approaches and heuristic approaches to validation. It is important that the decision to use or reject a particular technique for validation is based on a rational and objective selection approach. This paper suggests a framework to support this selection approach.
Author(s): A. Duffy, A. Orlandi
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 165 KB

Title: Using MATLAB to Control Commercial Computational Electromagnetics Software
Abstract: This paper provides details on how to use MATLAB to control some commercial electromagnetics software packages. FEKO is an example that can be directly called from MATLAB. Other commercial software, such as CST Microwave Studio and Ansoft HFSS, require a scripting language interface. An example of a design of an inset rectangular patch antenna is presented using a direct call to FEKO and a Visual Basic for Applications interface to CST Microwave Studio are presented.
Author(s): R. L. Haupt
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 176 KB

Title: Quantifying EMC Measurement Accuracy Using Feature Selective Validation
Abstract: It is commonplace in the field of Computational Electromagnetics (CEM) for engineers to validate models against experimental results. In some cases, this is performed with little understanding about the accuracy of the experimental data used to validate the underlying calculations from which Electromagnetic models are formed. This paper therefore explores the accuracy and more importantly the areas of inaccuracy and variability that may be associated with experimental data. The Feature Selective Validation (FSV) method is used to assess each area of variability, and thus quantify the quality of test configurations and test samples. In examining experimental repeatability rather than comparison to electromagnetic analysis results, this paper concludes that, while substantial variation between experimental results can exist, the use of FSV provides considerable assistance in quantifying repeatability and therefore assigning confidence to measurements against which CEM results can be compared. While this paper is based on experience in the automotive sector, it is anticipated that these findings are more widely applicable.
Author(s): A. Denton, A. Martin, A. Duffy
File Type: Journal Paper
Issue:Volume: 23      Number: 1      Year: 2008
Download Link:Click here to download PDF     File Size: 476 KB