ACES Publication Search
There are 14 search results for:
| Title: | ACES December 2009 Full Journal |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 9852 KB |
| Title: | ACES December 2009 Front/Back Matter |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 365 KB |
| Title: | Computational Electromagnetics and Model-Based Inversion: A Modern Paradigm for Eddy-Current Nondestructive Evaluation |
| Abstract: | This is the first of a planned series of papers in which we demonstrate the application of computational electromagnetics, especially the volume-integral method, to problems in eddycurrent nondestructive evaluation (NDE). In particular, we will apply the volume-integral code, VIC-3D, to solve forward and inverse problems in NDE. The range of problems that will be considered spans industries from nuclear power to aerospace to materials characterization. In this paper we will introduce the notion of model-based inversion, emphasizing the role of `estimationtheoretic metrics' to the practical application of inverse theory. |
| Author(s): | H. A. Sabbagh, R. K. Murphy, E. H. Sabbagh, J. C. Aldrin, J. Knopp, M. Blodgett |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 900 KB |
| Title: | Adaptive Arrays |
| Abstract: | This paper presents some types of adaptive antennas and the historical development of adaptive antennas. It explains some of the common algorithms associated with digital beamforming then presents techniques for adaptation using conventional arrays with corporate feeds, including the use of reconfigurable antenna elements. |
| Author(s): | R. Haupt |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 876 KB |
| Title: | Study of Exact and High-Frequency Code Solvers for Applications to a Conformal Dipole Array |
| Abstract: | The embedded element pattern of a conformal dipole array of seven elements is calculated using integral equation algorithms in exact solvers such as FEKO and WIPL-D, with the central element excited and other elements matchterminated in a 50? load. A technique is developed that uses the FEKO subdomain basis function current weights to derive the equivalent current weight for a single entire domain basis function for use in the high-frequency code NECBSC. This process includes effects of mutual coupling in the NECBSC calculations. The results for the embedded element pattern for cylinders with ???????? = 10, 20, 30, 40, 60 and 80, computed via FEKO, WIPL-D, and NECBSC, reveal discrepancies in the deep shadow (or creeping wave) regions. Parametric simulation studies for dipole currents, by varying the cylinder radius or radial distance of the array arc from the cylinder curved surface, are also included. |
| Author(s): | S. D. Walker, D. Chatterjee |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 756 KB |
| Title: | Design and Fabrication of an Axial Mode Helical Antenna |
| Abstract: | Given generalized requirements for a medium gain circularly polarized (CP) antenna we design and fabricate an axial mode helical antenna. This well known antenna has a relatively wide (1.7:1) bandwidth with gain proportional to the overall length. The antenna and ground plane diameters are determined by the chosen center frequency of operation. We evaluate the antenna design using FEKO electromagnetic simulation software for a center frequency of 700 MHz. We then fabricate one prototype with center metal rod support and foam core as in the conventional construction. We also desire a hollow core variant and use fiberglass to support the helical antenna. We present the measured results for these two types of construction compared to model results. Although the helical antenna embedded in fiberglass is a very rugged design it also involves sufficient dielectric loading to shift the antenna bandwidth to lower frequencies. |
| Author(s): | W. Coburn, C. Ly, T. Burcham, R. Harris, A. Bamba |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 815 KB |
| Title: | Rotman Lens Amplitude, Phase, and Pattern Evaluations by Measurements and Full Wave Simulations |
| Abstract: | Microwave lens’ performance is depicted by several parameters such as phase error, amplitude taper, and array scan pattern etc. For decades, these parameters have been estimated by the geometry optics method that does not capture the mutual couplings within the lens geometry. Full wave simulation toolkits to conduct EM prediction are now available. However, using them to synthesize and optimize the electrical performance of Rotman lens is still relatively new. Several microwave lens full wave simulations have been attempted using different methods, such as FDTD, FEM, and FIT. They were reported from the perspectives of either phase or amplitude predictions at a single port or single frequency. However, the lens properties at multiple frequencies and for multiple beam ports using MoM have not been investigated. In this paper, we address such simulations using the planar Green’s function in FEKO. The phase, amplitude and array factor across the frequency band for multiple beam ports are compared with the measured results, and their errors are evaluated. Prominent agreement between FEKO and measurement is demonstrated. The performance of a prototype lens is presented, followed by discussing few future aspects of lens optimization using full wave simulations. |
| Author(s): | J. Dong, A. I. Zaghloul, R. Sun, C. J. Reddy, S. J. Weiss |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 1200 KB |
| Title: | FEKO Simulation of a Wedge Mounted Four Element Array Antenna |
| Abstract: | A four element patch array with main beam locations approaching endfire has been developed. The initial design was accomplished using EMAG’s EMPicasso software. The array is intended to be used in a monopulse configuration on the sides of a wedge-like structure. As such, accurate estimations of the patterns need to be obtained when the antenna is mounted on the geometry of the wedge. These simulations were not possible with 2.5 dimensional software, such as EMPicasso (www.emagware.com). We present measured data as compared to simulations using FEKO (www.feko.info) software for the array on a wedge. |
| Author(s): | S. Weiss, W. Coburn, O. Kilic |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 583 KB |
| Title: | Infinite Periodic Boundary Conditions in FEKO |
| Abstract: | Infinite periodic boundary conditions (PBC’s) implemented in FEKO are presented. To enable the analysis of a wide variety of problems, the PBC includes dielectric objects, metallic surfaces, metallic wires and connection points between wires and surfaces. In addition, the geometry is allowed to touch the periodic boundaries (i.e. continuous current flow onto the neighboring cell which requires special basis function treatment). |
| Author(s): | J. van Tonder, U. Jakobus |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 2812 KB |
| Title: | A Mode Selecting Eigensolver for 2D FIT Models of Waveguides |
| Abstract: | For the computation of eigenmodes in multimodal waveguide structures, the Jacobi- Davidson eigenvalue solver is extended by a vector-based weighting function. It allows to generate only modes with a desired field distribution. The performance of this solver is studied by means of an eigenmode computation in a photonic crystal fiber which is discretized by the finite integration technique. The new algorithm is able to separate the modes in the fiber core from a number of non-physical modes which originate from a transversal PML-type boundary condition. |
| Author(s): | B. Bandlow, R. Schuhmann |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 461 KB |
| Title: | Multi-Fidelity Optimization of Microwave Structures Using Response Surface Approximation and Space Mapping |
| Abstract: | A computationally efficient method for design optimization of CPU-intensive microwave structures is discussed. The presented technique exploits a response surface approximation surrogate model set up using data from the coarse-mesh EMbased model being a relaxed-accuracy representation of the microwave structure in question. The surrogate model is further subjected to the classical space mapping optimization. It is demonstrated that the new technique is able to provide a satisfactory design with a few electromagnetic simulations of the original structure. Because of using functional approximation, no circuit equivalent coarse model is necessary, which makes the presented approach particularly suitable for structures for which the development of the reliable coarse model is problematic (e.g., antennas). |
| Author(s): | S. Koziel |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 639 KB |
| Title: | Modeling of UIC Cables in Railway Systems for Their Use as Power Line Communication Channels |
| Abstract: | In this paper the authors investigate the possibility of using the preexisting electrical-control grid onboard trains as a wideband communication channel. In particular the attention is focused on a particular class of cables (UIC) present in most trains. A model and a set of simulations are presented in the paper, showing that the PLC technology can be used in this new environment. |
| Author(s): | S. Barmada, A. Gaggelli, P. Masini, A. Musolino, R. Rizzo, M. Tucci |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 1024 KB |
| Title: | Enhancing Microwave Breast Tomography with Microwave-Induced Thermoacoustic Imaging |
| Abstract: | Finite-element based microwave to- mographic system can successfully recover dielectric properties of the human breast, aiming to image malignant breast tissues. When compared with mi- crowave radar imaging, microwave tomography re- quires simpler electronics and antenna design due to its narrowband operation. However, the narrowband feature limits the resolution of the nite-element mesh often used to recover the dielectric properties of the breast, as there is no a priori information for mesh re nement in the critical location within the breast. In this paper, we present a two-dimensional model of a microwave imaging system with monopole antennas and pressure sensors placed in an interleav- ing arrangement around the breast in its pendant position. The proposed system would synergistically function together with the microwave tomographic modality in a fashion that is envisioned as follows: (1) The system uses a monopole antenna to trig- ger microwave absorption and, consequently, heating and expansion of the tumor. (2) The array of pres- sure transducers placed around the breast detect the thermally-induced pressure signals. (3) These signals are used to construct a preliminary breast image. (4) The image is used to generate a non-uniform nite- element mesh, with increased re nement around the suspected tumor locations. (5) The re ned mesh is fed to an algorithm utilized by the microwave tomo- graphic system to solve the inverse problem, which will now have a priori information and will hence have improved resolution in its resulting image. |
| Author(s): | G. Zhu, M. Popovic |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 564 KB |
| Title: | Electrodynamics of Dipolar Beads in an Electrophoretic Spherical Cavity |
| Abstract: | The transient dynamics of dipolar beads in an electrophoretic spherical cavity presents an interesting phenomenon, because it captures the interplay of electrophoretics, particle dynamics, and tribology. The problem geometry is described by a dipolar bead immersed in a polarized fluid within the cavity. Switching bias voltages are applied to induce both translational and rotational motion of the bead. This paper details a model of coupled phenomena which employs ODE’s to describe the bead dynamics, integral equations for the field solution, and particle simulation for the bipolar migrations. Special focus is given to the impact of confinement and gravitational force on the bead dynamics. |
| Author(s): | M. H. Lean, A. R. Völkel |
| File Type: | Journal Paper |
| Issue: | Volume: 24 Number: 6 Year: 2009 |
| Download Link: | Click here to download PDF File Size: 343 KB |