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Title: Full February 2009 Journal
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 8477 KB

Title: February 2009 Journal Front/Back Matter
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 304 KB

Title: A Review and Application of the Finite-Difference Time-Domain Algorithm Applied to the Schrodinger Equation
Abstract: This paper contains a review of the FDTD algorithm as applied to the time-dependent Schrodinger equation, and the basic update equations are derived in their standard form. A simple absorbing boundary condition is formulated and shown to be effective with narrowband wave functions. The stability criterion is derived from a simple, novel perspective and found to give better efficiency than earlier attempts. Finally, the idea of probability current is introduced for the first time and shown how it can be used to radiate new probability into a simulation domain. This removes the need to define an initial-valued wave function, and the concept is demonstrated by measuring the transmission coefficient through a potential barrier.
Author(s): J. R. Nagel
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 901 KB

Title: Wide-Angle Absorbing Boundary Conditions for Low and High-Order FDTD Algorithms
Abstract: Wide-angle performance of the perfectlymatched- layer absorbing boundary conditions for the finite-difference time-domain (FDTD) method is investigated for efficient modeling of electrically large structures. The original split-field, uniaxial and convolutional perfectly-matched-layer formulations are all optimized to produce near-flat absorption for incidence angles up to 87 degrees. Optimized wide-angle parameters are derived for both the standard FDTD method and a high-order finite-volumes-based variant. The investigated high-order algorithm in particular is shown to produce improved wide-angle performance over standard FDTD for all three perfectly-matched-layer variants even when they are optimized for normal wave incidence. In all cases, optimization is managed through appropriate choices of modeling parameters which can be directly and unobtrusively applied to existing FDTD codes.
Author(s): Mohammed F. Hadi
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 113 KB

Title: Extension of the 2-D CP-FDTD Thin Slot Algorithm to 3-D for Shielding Analysis
Abstract: The two-dimensional CP-FDTD thin slot algorithm is extended to three-dimensions for the application to shielding analysis in electromagnetic compatibility. The accuracy and the applicability of the 3-D CP-FDTD scheme to the slot width were validated with finer mesh model and capacitive thin-slot formalism (C-TSF). The model taken by the comparison is originated from a thin slot in an enclosure wall. The numerical results indicate that the performance or accuracy will descend with the augment of the slot width. Good agreements with the results of finer mesh modeling can be expected as the slot width is on the order of the mesh dimension, and quite large discrepancies from the results of C-TSF with the slot width far less than mesh dimension. The 3D CP-FDTD algorithm will be utilized when the slot width is comparatively large and otherwise C-TSF will be used. Taking advantage of both of them will avoid finer mesh in thin slots modeling such as the shielding analysis of the electronic enclosure.
Author(s): Xu Li, Ji-h. Yu , Q.-di Wang , Y.-ming Li
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 400 KB

Title: A New Implementation of the Hybrid Taguchi GA: Application to the design of a Miniaturized Log-Periodic Thin-Wire Antenna
Abstract: This paper proposes a modification of the hybrid Taguchi-genetic algorithm (HTGA) for solving global numerical optimization problems with continuous variables. The HTGA is a method that combines a conventional genetic algorithm (CGA), which has a powerful global exploration capability, with the Taguchi method, which can exploit the optimum offspring. The Taguchi method is utilized in the HTGA to help in selecting the best genes in the crossover operations. The new implementation proposed in this paper (nHTGA) involves producing, at each generation, a single offspring by Taguchi method, one of its parents being the best individual found so far, instead of repeatedly applying Taguchi to generate several individuals with both parents selected at random as HTGA does. Moreover, the efficiency of the algorithm is enhanced by only crossing via Taguchi individuals with a high enough number of different genes. The performance of the proposed HTGA is assessed by solving several benchmark problems of global optimization with large number of dimensions and very large numbers of local minima. The computational experiments show that the new algorithm causes a reduction, sometimes drastic, in the number of function calls, i.e. in computational time, for all the benchmark problems proposed. As an example of application of this novel algorithm to a real-world problem, the optimization of an ultra-broadband zigzag log-periodic antenna is carried out and discussed.
Author(s): C. M. de J. van Coevorden, A. R. Bretones, M. F. Pantoja, S. G. Garcıa, A. Monorchio
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 2171 KB

Title: Analysis of the Behavior of Sierpinski Carpet Monopole Antenna
Abstract: Three fractal monopole antennas using the Sierpinski carpet geometry is described in this paper. The idea for these designs is gotten from semi-log-periodic behavior of fractal antenna. In this paper, we noted input impedance matching of antennas throughout the passband of them. In this point of view, we will apply the wideband, broadband and multiband for these antennas. Our first wide-band design is named antenna-1. This has a good input impedance match throughout the passband 2-20GHz. Second antenna is named antenna-2. This antenna has an interesting behavior while has a multiband behavior from 1-7GHz and has broad-band behavior from 7-20 GHz. However, because of two slots in ground plane of this antenna, the 6-7GHz band is eliminated. Third of antennas is named antenna-3. It has a multi-band behavior from 0.5-17GHz. On average, we could match input impedance of proposed antennas, for three desired behavior. The dimension of main- square for antenna-1, antenna-2 and antenna-3 is 45, 60 and 132 mm respectively. These antennas are suitable for the operating bands of GSM, ICMS, UMTS, Bluetooth, WLAN and HIPERLAN systems.
Author(s): M. Naghshvarian-Jahromi, N. Komjani-Barchloui
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 1072 KB

Title: Design of Elliptical Dielectric Resonator Antennas Using Genetic Algorithm and Rayleigh-Ritz Technique
Abstract: In this paper, a specialized genetic algorithm (GA) combined with Rayleigh-Ritz method is used to obtain the dimensions of elliptical dielectric resonators (EDRs) for dual-band, wide-band, or circular polarization (CP) operation. Slot-coupled elliptical dielectric resonator antennas (EDRAís) and their characteristics are investigated. Parametric studies are presented to study the dependence of the return loss on the slot parameters. These parametric studies are used to optimize the slot dimensions and its position to excite given desired modes.
Author(s): A. Tadjalli, A. Sebak, T. Denidni, I. Ahadi-Akhlaghi
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 500 KB

Title: A Closed-Form Rational Model of Coupled Right/Left-Handed Ladder Networks for New Microwave Circuits Design
Abstract: The analytical characterization of coupled composite righ/left-handed ladder networks is presented. Relying on closed-form polynomials, the two-port representation of the composite right/left-handed ladder network is obtained in a rational form, leading to identify its poles and residues and, thus, the state-space macromodel of the network. The proposed macromodel is successfully validated by comparing the numerical results with those obtained using conventional frequency domain techniques of finite periodic structures.
Author(s): G. Antonini
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 434 KB

Title: Functional Imaging of Compressed Breast by Microwave Radiometry
Abstract: A tumor is visible by a passive microwave radiometer scanning the breast surface if it changes the radiometer output of a healthy breast to an extent that overcomes the radiometric resolution for the given sensing antenna and integration time. In this paper the breast is intentionally squeezed between the radiometric antenna and the chest wall and the temperature is evaluated for the deformed breast together with the generated radiometric signal. To be compared with the radiometric resolution, the difference signal between the outputs in the presence of a lesion and in its absence has to be evaluated. To achieve this, a mechanical, thermal and electromagnetic model of the breast has been developed. A finite-element code has been used to solve for the mechanical and thermal problems, while FDTD has been exploited for electromagnetic computations. We show that compressing the breast improves the radiometric visibility depending on tumor depth and deformation.
Author(s): S. Iudicello, F. Bardati
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 2062 KB

Title: Analysis and Estimation of Surge Impedance of Tower
Abstract: Different mathematical formulas and analytical values of surge impedance of communication tower including high voltage transmission and distribution tower are presented. Those values and formulas have been utilized since 1934. Recently, the surge impedance of communication tower under the influence of direct and indirect lightning hit has drawn a lot of attention. Such value of lightning surge impedance and its associated parameters are becoming important factors for the protection system design in substation as well as low voltage communication equipments including home appliances.
Author(s): M. O. Goni , A. Ametani
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 295 KB

Title: A Novel Greenís Function Analysis of Wave Scattering by an Infinite Grating using Complex Images Technique
Abstract: A new method, based on the complex images technique is presented for solving the electromagnetic scattering from the infinite metallic and dielectric gratings. The main idea of this method lies in representing the infinite summation of the structure period Green's functions in terms of finite summations of complex images. The method of moments (MoM) is then employed to find the current distribution, reflection and transmission coefficients of the gratings. The validity of the presented method is shown through various examples for different grating geometries and incident wave polarizations. Fast convergence, simple formulations and flexibility of the method in analyzing different structures are the main advantages of the proposed method.
Author(s): H. Alaeian, R. Faraji-Dana
File Type: Journal Paper
Issue:Volume: 24      Number: 1      Year: 2009
Download Link:Click here to download PDF     File Size: 313 KB