ACES Publication Search
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| Title: | ACES December 2011 Full Journal |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 4271 KB |
| Title: | ACES December 2011 Front/Back Matter |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1041 KB |
| Title: | Performance of Single and Double T-matched Short Dipole Tag Antennas for UHF RFID Systems |
| Abstract: | The impact of tag antenna and chip impedance tolerances on power transfer between these components is investigated analytically. Means for efficient computation of the minimum and maximum power transmission coefficient under given impedance tolerances are developed. The presented sensitivity analysis is employed to quantify the design uncertainty of single and double T-matched short dipole tag antennas for UHF RFID systems. The simulated and measured performance of the two tag antennas is analyzed and compared. |
| Author(s): | T. Björninen, A. Z. Elsherbeni, L. Ukkonen |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1212 KB |
| Title: | FEKO/NEC2 Simulation of Candidate Antennas for the Long Wavelength Array (LWA) |
| Abstract: | This paper presents FEKO and NEC-2 simulations done on three dipole-like structures; the big blade, the tied-fork and the fork antenna. These antenna elements are considered for the design of the long wavelength array (LWA). The LWA is an interferometer under construction in New Mexico, USA for astronomical observations in the 20 - 80 MHz spectrum. This paper presents the simulation results of a co-polarized antenna gain patterns, impedance values, and mutual couplings for each candidate elements. Coupling results from FEKO and NEC-2 simulations are compared with measurement result of the big blade antenna. The paper also presents Sparameters for 25 elements of the tied-fork antennas. |
| Author(s): | N. Fekadu, A. I. Zaghloul |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1178 KB |
| Title: | Electromagnetic Launch Vehicle Fairing and Acoustic Blanket Model of Received Power using FEKO |
| Abstract: | Evaluating the impact of radio frequency transmission in vehicle fairings is important to electromagnetically sensitive spacecraft. This study employs the multilevel fast multipole method (MLFMM) from a commercial electromagnetic tool, FEKO, to model the fairing electromagnetic environment in the presence of an internal transmitter with improved accuracy over industry applied techniques. This fairing model includes material properties representative of acoustic blanketing commonly used in vehicles. Equivalent surface material models within FEKO were successfully applied to simulate the test case. Finally, a simplified model is presented using the Nicholson Ross Weir derived blanket material properties. These properties are implemented with the coated metal option to reduce the model to one layer within the accuracy of the original three layer simulation. |
| Author(s): | D. H. Trout, J. E. Stanley, P. F. Wahid |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1237 KB |
| Title: | Evaluation of Lightning Induced Effects in a Graphite Composite Fairing Structure |
| Abstract: | Defining the electromagnetic environment inside a graphite composite fairing due to near-by lightning strikes is of interest to spacecraft developers. This effort develops a transmission-line-matrix (TLM) model with CST Microstripes to examine induced voltages on interior wire loops in a composite fairing due to a simulated near-by lightning strike. A physical vehicle-like composite fairing test fixture is constructed to anchor a TLM model in the time domain and a FEKO method of moments model in the frequency domain. Results show that a typical graphite composite fairing provides attenuation resulting in a significant reduction in induced voltages on high impedance circuits despite minimal attenuation of peak magnetic fields propagating through space in near-by lightning strike conditions. |
| Author(s): | D. H. Trout, J. E. Stanley, P. F. Wahid |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1241 KB |
| Title: | Analysis of Transient Electromagnetic Scattering from an Overfilled Cavity Embedded in an Impedance Ground Plane |
| Abstract: | In this paper, we consider the timedomain scattering problem of a two-dimensional overfilled cavity embedded in an impedance ground plane. An artificial boundary condition is introduced on a semicircle enclosing the cavity that couples the fields from the infinite exterior domain to those fields inside. The problem is first discretized in time using the Newmark scheme, and at each time step, we derive the variational formulation for the TM polarization, and establish well-posedness. Numerical implementation of the method for both the planar and overfilled cavity models is also presented. |
| Author(s): | R. S. Callihan, A. W. Wood |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1115 KB |
| Title: | Coupled Electromagnetic Field Computation with External Circuit for the Evaluation the Performance of Electric Motor Designs |
| Abstract: | In this paper, a set of PM machine's designs, having the similar level of nominal input and outputs i.e. voltage, torque, and speed were compared to evaluate the effectiveness of a computational design procedure. The designs include the machines with distributed winding arrangements, different number of slots, different pole widths, and different slot opening shapes. The physical characteristics of machines such as the cogging torque, back emf, flux linkages, and inductances were calculated from a 2D nonlinear transient finite element analysis with motion. The torque and speed profiles of all of the machines were calculated from the phase variable modeling approach. The phase variable model is a database representation of the machine's numerical model and it allows computationally efficient dynamic simulation of the coupled problem with realistic physics-based design. The phase variable models of the machines were linked to the driving circuit to determine the mutual effect of machine design parameter and the drive topology on the performance measures of machines. |
| Author(s): | A. Sarikhani , O. A. Mohammed |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1828 KB |
| Title: | Adaptive Design Specifications and Coarsely-Discretized EM Models for Rapid Optimization of Microwave Structures |
| Abstract: | A simple and efficient procedure for EM-simulation-driven design optimization of microwave devices is discussed. Our approach exploits recently introduced adaptively adjusted design specifications technique that shifts the optimization burden into a relaxed-accuracy and computationally cheap (low-fidelity) model of the structure under consideration, evaluated using the same EM solver as the original (high-fidelity) model but with coarse discretization. The unavoidable misalignment between the low- and high-fidelity models is accounted for by suitable adjustments of the design specifications. The presented method is simple to implement and allows rapid design improvement as demonstrated through examples. |
| Author(s): | S. Koziel |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1050 KB |
| Title: | Direct Field and Mixed Potential Integral Equation Solutions by Fast Fourier Transform Accelerated Multilevel Green’s Function Interpolation for Conducting and Impedance Boundary Objects |
| Abstract: | A fast solver based on multilevel Lagrange interpolation of homogenous space electric and magnetic field Green’s functions is discussed. Broadband applications are possible due to a wavelength adaptive multilevel scheme. By an FFT-technique, the pertinent translation operators are diagonalized. An impedance boundary condition (IBC) is employed considering electric and magnetic currents for the approximate treatment of non-metallic objects. The common mixedpotential integral equation and a direct field formulation are both discussed. In general, the direct field formulation leads to more accurate results in conjunction with interpolated Green’s functions, especially for low frequency problems. The efficiency of the algorithm is shown in several numerical examples. |
| Author(s): | D. T. Schobert , T. F. Eibert |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1149 KB |
| Title: | An Implementation of King’s Green Functions in Thin Wire Scattering Problems |
| Abstract: | We investigate electromagnetic scattering from metallic thin wire structures located over planar and spherical lossy dielectric half-spaces by applying Green’s function formulation and method of moments in the resonance region and under “high contrast approximation” (HCA). For this purpose, in the calculations of the impedance matrix and the potential column of the moment system, we employ the Green functions of King valid for arbitrary range under HCA and the asymptotic (far field) Green functions for planar and spherical impedance surfaces delivered by Norton and Wait, respectively. For a verification of the developed codes, the current distributions obtained under plane wave illumination on the arms of a cross shaped thin wire structure are compared to the same results obtained by the commercial software SNEC™. Various illustrations for the scattered electrical field from a thin wire plate located over planar and spherical half-spaces are also presented. |
| Author(s): | Ö. Zor, B. Polat |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1240 KB |
| Title: | Simulation and Design of a Tunable Patch Antenna |
| Abstract: | A method for designing a tunable microstrip patch antenna is presented, suggesting cooperation between a theoretical transmission line model and a professional electromagnetic simulation tool. Tunable impedance elements are used to perturb the microstrip patch to alter the tuning range of the antenna. Results show excellent correlation between theoretical calculations and simulation data from Sonnet. Finally, guidelines for designing an antenna to be excited by an IMPATT diode are discussed. |
| Author(s): | B. D. Horwath, T. Al-Attar |
| File Type: | Journal Paper |
| Issue: | Volume: 26 Number: 12 Year: 2011 |
| Download Link: | Click here to download PDF File Size: 1121 KB |