ACES Publication Search
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| Title: | ACES January 2010 Full Journal |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 9311 KB |
| Title: | ACES January 2010 Front/Back Matter |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 349 KB |
| Title: | A Summary Review on 25 Years of Progress and Future Challenges in FDTD and FETD Techniques |
| Abstract: | The finite-difference time-domain (FDTD) method has established itself among the most popular methods for the numerical solution of Maxwell equations. Reasons for its popularity include its versatility, matrix-free characteristic, ease for parallelization, and low computational complexity. In recent years, the finite-element time-domain (FETD) has also become another very popular algorithm for solving time-domain Maxwell equations due to its geometrical flexibility and the steady growth in hardware computing power. In this review, we succinctly recollect some of the milestones in the development of FDTD and FETD over the last 25 years, and briefly discuss some challenges for the future development of these two algorithms. |
| Author(s): | F. L. Teixeira |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 274 KB |
| Title: | Integral Equation Methods for Near-Field Far-Field Transformation |
| Abstract: | Antenna measurements are often carried out in the radiating near-field of the antenna under test. Near-field transformation algorithms determine an equivalent sources representation of the antenna in an inverse process and field values in almost arbitrary distances can be computed. In this paper two integral equation methods for the near-field transformation are presented, which are especially suitable for electrically large antennas, irregular sample point distributions, higher order probes, and non-ideal measurement environments. |
| Author(s): | C. H. Schmidt, T. F. Eibert |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 1037 KB |
| Title: | FPGA Accelerated Phased Array Design Using the Ant Colony Optimization |
| Abstract: | The objective of this paper is to investigate the utilization of field programmable gate arrays (FPGA) in the field of electromagnetics by applying the ant colony optimization (ACO) method in the design of phased array antennas for multiple beam satellite communication systems. The amplitudes of the array elements are optimized to reduce the cochannel interference in a multiple beam satellite communication system. The potential gains in the speed of the calculations are investigated in comparison to conventional simulation techniques of the same application on a regular PC. Two different FPGA platforms and implementation approaches are compared for performance to two software developments implemented using Matlab and C languages. It has been shown that significantly accelerated performance can be achieved for the particular application. This kind of speed improvement can enable handling more complex requirements and constraints for the same application in a very reasonable amount of time, which would otherwise be impossible with conventional computational platforms and techniques. This magnitude of speed improvement is due to the configurable nature of the FPGAs. Unlike central processing units (CPU) in a conventional computer, which have to deal with a preset set of instructions to properly function; FPGAs are completely programmable to carry out a set of functions in the most efficient manner for the particular algorithm at hand. In this study, the FPGA has been configured to function as an efficient “ACO machine.” Both parallelization and pipelining have been utilized to achieve this performance. The details of the implementation on the FPGA platform and the achieved acceleration are discussed in the paper. |
| Author(s): | O. Kilic |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 351 KB |
| Title: | A Simplified Model for Normal Mode Helical Antennas |
| Abstract: | Normal mode helical antennas are widely used for RFID and mobile communications applications due to their relatively small size and omni-directional radiation pattern. However, their highly curved geometry can make the design and analysis of helical antennas that are part of larger complex structures quite difficult. A simplified model is proposed that replaces the curved helix with straight wires and lumped elements. The simplified model can be used to reduce the complexity of full-wave models that include a helical antenna. It also can be used to estimate the performance of a helical antenna without fullwave modeling of the helical structure. |
| Author(s): | C. Su, H. Ke, T. Hubing |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 768 KB |
| Title: | Antenna Developments for Military Applications |
| Abstract: | A review of current, past and projected activities in antenna development indicates a broad spectrum of requirements, and subsequently a variety of innovations to meet these requirements for military radar and communications systems. Designing the antennas in the operating environment, known as in-situ design, is an important factor in guaranteeing the successful operation of the antenna in the field. This paper presents the basic blocks in antenna development, followed by examples of some antennas developed at the Army Research Laboratory for military systems and applications. These include Rotman lenses as beam formers for electronically scanning arrays; phased arrays using MEMS phase shifters at 30 GHz; a 76-GHz narrow beam, low-sidelobe antenna for collision avoidance radar; and other specialized antennas. Of special interest is an effort on developing and using metamaterials in antenna designs, where practical realizations of such materials have the potential of improving the performance and reducing the size of antennas. |
| Author(s): | A. I. Zaghloul, S. J. Weiss, W. K. Coburn |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 1198 KB |
| Title: | Low-profile, Broadband Polarization Converting Surface Ground Planes for Antenna Polarization Diversity |
| Abstract: | A broadband antenna backed by a polarization converting surface ground plane is presented. The conversion of reflected field polarization provides diversity from a single, linearly polarized antenna, while avoiding broadside nulls in the radiation pattern as a function of frequency. Results for a low-profile dipole planar inverted cone antenna ~?/10 above a polarization converting surface indicate greater than 40% bandwidth. Comparison with solid ground planes and high impedance ground planes are discussed, with polarization diversity and lack of broadside nulls identified as key advantages to the proposed design. |
| Author(s): | B. A. Lail, K. Y. Han |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 543 KB |
| Title: | A Numerical Study of Coaxial Helical Antennas |
| Abstract: | A FEKO model was constructed to investigate two helical antennas integrated coaxially on a shaped ground plane. One antenna was designed to have a reasonable gain and axial ratio (AR) from 0.5 – 0.9 GHz and the other from 1.0 – 1.6 GHz. In principle, the antennas could be connected in parallel to provide a near 50 ? input impedance and act as a wideband antenna. However, this connection is problematic and can make fabrication more complex while changing the input impedance in unpredictable ways. An alternative is to use a microstrip impedance transformer to provide a 50 ? input to each antenna. Then a broadband splitter can be used for a single feed wideband antenna. Otherwise, these two ports with switched input allow dual-band operation. The FEKO model is described and simulation results are presented for both cases. These results encourage further virtual prototyping and prototype fabrication for model validation. |
| Author(s): | W. K. Coburn |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 557 KB |
| Title: | Analysis of Multi-Layer Composite Cavity Using FEKO |
| Abstract: | Modeling of a large cavity containing multiple layers inside the structure has been studied using equivalent impedance approximations along with simplified single ray tracing analysis. This modeling effort investigates the effects of radiating with a source enclosed in a large vacant composite structure relative to a short wavelength. The development of the model involves the completion of a two step process. First, the heritage geometric reduction and approximation is investigated. This particular investigation involves an approach that is an application of Poynting’s Theorem. This work was performed by Hallett and Reddell at Goddard Space Flight Center in 1998. For this comparison, the Multi-Level Fast Multipole Method (MLFMM) available in the commercial tool FEKO, is used to model a generic multi-layer payload fairing (hollow cone connected to a hollow cylinder) with a radiating source to determine the resonant cavity effects within the fairing as another approximation baseline. The intent is to provide predictions for the electric field levels if a transmitter in the fairing either deliberately or unintentionally is activated. The results show a comparison with the heritage calculation and FEKO software tool. However, FEKO shows the electric field distributions within the composite fairing cavity instead of a single average value. |
| Author(s): | J. E. Stanley, D. H. Trout, S. K. Earles, I. N. Kostanic, P. F. Wahid |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 206 KB |
| Title: | Calibration and Evaluation of Body Interaction Effects for the Enhancement of a Body-Borne Radio Direction Finding System |
| Abstract: | A method of moments (MoM) based computational study and design of a body-borne direction finding (DF) system is investigated in this paper. A baseline two-sensor DF system is established, and the performance of this system is characterized with measurements and simulation. A cylindrical human body model is then introduced to the system as a passive scatterer. Computer models of the body-borne system are validated using measurements with a prototype human body phantom. A parametric system response study is performed on the most important model variables to identify system stability. A discussion is presented on how these data may be applied to a direction finding function to generate a direction finding solution. This work clearly demonstrates the ability of modern computational electromagnetics tools to accurately and efficiently predict the response of complex physical systems. |
| Author(s): | A. Lalezari, F. Lalezari, D. S. Filipovic |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 3951 KB |
| Title: | Application of the Normalized Surface Magnetic Source Model to a Blind Unexploded Ordnance Discrimination Test |
| Abstract: | The Normalized Surface Magnetic Source (NSMS) model is applied to unexploded ordnance (UXO) discrimination data collected at Camp Sibert, AL, with the EM63 electromagnetic induction sensor. The NSMS is a fast and accurate numerical forward model that represents an object’s response using a set of equivalent magnetic dipoles distributed on a surrounding closed surface. As part of the discrimination process one must also determine the location and orientation of each buried target. This is achieved using a physics-based technique that assumes a target to be a dipole and extracts the location from the measured magnetic field vector and the scalar magnetic potential; the latter is reconstructed from field measurements by means of an auxiliary layer of magnetic charges. Once the object’s location is estimated, the measured magnetic field is matched to NSMS predictions to determine the timedependent amplitudes of the surface magnetic sources, which in turn can be used to generate classifying features. This paper shows the superior discrimination performance of the NSMS model. |
| Author(s): | F. Shubitidze, J. P. Fernandez, I. Shamatava, L. R. Pasion, B. E. Barrowes, K. O'Neill |
| File Type: | Journal Paper |
| Issue: | Volume: 25 Number: 1 Year: 2010 |
| Download Link: | Click here to download PDF File Size: 907 KB |