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Title: ACES Journal November 2012
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
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Title: ACES Journal November 2012 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 632 KB

Title: Analytical and FEM Based Calculation of Electromagnetic Forces Exerted on Cylindrical Coils due to their own Current
Abstract: Different parts of the cylindrical coils are exposed to electromagnetic forces due to electric current flowing through it. These forces can deform the coil in axial and radial directions in abnormal operating conditions. So, in design process of cylindrical coils in many magnetic devices, mechanical stresses exerted on different parts of these kinds of coils should be determined. In this paper, analytical expressions for the forces in axial direction are derived in order to calculate the forces exerted on different parts of the cylindrical coils. In order to evaluate the precision of the method, the finite element method (FEM) is used and the results obtained by FEM are compared with the results of the analytical equations. Results obtained by finite element analysis confirm the analytical method. Due to inherent difficulties in calculation of the forces in radial direction, distribution of the latter on the coil body is calculated by FEM. The results show that the outer turns of the coil in two axial ends are exposed to the largest axial tension, while radial stresses are largest in the middle parts of the coil. In this paper, the calculations focus on the cylindrical coils; however, the method can be used for the calculation of the magnetic force distribution on different parts of spiral coils, disc coils and any type of air-cored coils with different sizes.
Author(s): A. Shiri, D. E. Moghadam
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 943 KB

Title: Accelerated and Robust Computation of Time Domain Floquet Wave-Based Periodic Greenís Functions for TD Integral Equations Applications
Abstract: A novel approach has been introduced to remedy the computational complexities of the recently introduced time domain periodic Greenís functions in the 1D and 2D periodic case. Specifically, it has been shown that for a certain class of temporal basis functions, the computational cost of convolutions with temporal basis functions, which results in the band-limited GFs needed by most time domain integral equations solvers, can be considerably reduced, as compared to conventional methods that are currently in practice. It is also well known that the computational complexity of the Floquet-wave based Greenís functions increases when the point of observation approaches a source. Robust forms have been obtained for both 1D and 2D periodic TDGFs for any source-observation distance, which are then further improved for high-efficiency numerical implementation.
Author(s): M. Saviz, R. Faraji-Dana
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 850 KB

Title: Analytical Solution of Scattering by a 2D Dielectric Filled Crack in a Ground Plane Coated by a Dielectric Layer: TE Case
Abstract: Analytical solution of scattering by a 2D loaded crack on a ground plane, coated by a dielectric layer for TE case is studied theoretically using Kobayashi and Nomura's (Kobayashi Potential) method. The geometry is divided into three regions whose fields are expressed in terms of Bessel eigenfunctions. The problem is reduced to a system of equations involving truncated summations with an infinite number of unknowns. Excitation coefficients are determined by applying the boundary conditions. By applying Weber- Schafheitlin discontinuous integrals, the infinite summations could efficiently be truncated with high numerical accuracy. For validation, in addition to convergence analysis, near-field magnetic current densities on the crack and the radar cross section (RCS) results are compared with those of Finite Element Method (FEM). Having the analytical method, the influence of the filling and the dielectric layer is investigated.
Author(s): B. Ghalamkari, A. Tavakoli, M. Dehmollaian
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 810 KB

Title: Transform Method for Dielectric Periodic Interface Scattering
Abstract: An extended transform method is developed for calculating the 2-D scattering problem from dielectric periodic interfaces. The method transforms the problem into scattering from two imaginary planes, one of which cuts across the maximum points and another across the minimum points of the periodic interface. The fields just above and below the periodic interface are expanded into Taylor series with respect to the two planes respectively. Then by satisfying boundary condition, the unknown coefficients can be determined. Comparing with T-Matrix and MoM, proposed method is simpler in formulation and less in computational time. Near scattered field distributions above and in the trough region of the periodic interface are calculated by proposed method. The results are in good agreements with those of T-Matrix and MoM respectively.
Author(s): L. Li, T. L. Dong, P. Chen, B. Y. Chen, Q. Huang, L. Lang, Q. X. Li
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 670 KB

Title: New Alternating Direction Implicit Finite-Difference Time-Domain Method with Higher Efficiency
Abstract: This letter presents a new unconditionally stable three-dimensional alternating direction implicit finite-difference time-domain (ADI-FDTD) method. The implicit differences of the method along different directions are irrelevant to each other, which results in a new updating equation with much simpler and more concise right-hand sides. This leads to substantial reduction in the number of arithmetic operations required for their computations. The unconditional stability of the proposed method is presented analytically, and the numerical performance of the method over the conventional ADI-FDTD method is demonstrated through numerical example.
Author(s): J. Chen
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 631 KB

Title: Electromagnetic Band Gap (EBG) Superstrate Resonator Antenna Design for Monopulse Radiation Pattern
Abstract: A high directive electromagnetic bandgap (EBG) antenna operating in a wide frequency band is used to design a monopulse radiation pattern. Four aperture coupled microstrip antennas (ACMA) are used as feeding sources in this EBG antenna, and a frequency selective surface (FSS) is used as a superstrate layer. By suitable design of a wideband feeding network, it is possible to obtain a monopulse radiation pattern in E&H-Planes simultaneously. In this antenna, using the superstrate layer and the ACMA simultaneously, leads to produce a wide frequency band for the antenna reflection coefficient. Also, high directivity is achieved only by using the superstrate layer that has been made by the FSS layer with square loop elements. At first, a wideband ACMA is designed to operate in x-band. Secondly, after the design of optimum superstrate layer by the FSS structure, it is added to the four ACMA in order to increase both bandwidth and directivity. Finally, a wideband feeding network which operates in X-Band is designed to produce monopulse radiation pattern. The EBG antenna operates in three different modes including one sum radiation pattern and two difference radiation patterns in E&H-Planes simultaneously.
Author(s): A. Pirhadi, H. Bahrami, A. Mallahzadeh
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 1327 KB

Title: Triangular Patch Yagi Antenna with Reconfigurable Pattern Characteristics
Abstract: A pattern reconfigurable Yagi patch antenna is proposed. The antenna is composed of three triangular microstrip patches, i.e., one driven patch and two parasitic patches. By controlling switches, which are installed on the parasitic patches, the radiation pattern of the antenna can point to three different directions, covering an elevation range from -61į to +63į in the E-plane. The simulated and measured results are presented and they agree with each other in reasonable precision.
Author(s): J. Zhang, X. S. Yang, J. L. Li, B. Z. Wang
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 899 KB

Title: Directivity and Bandwidth Enhancement of Proximity-Coupled Microstrip Antenna Using Metamaterial Cover
Abstract: Two major problems associated with patch antennas are low gain and narrow bandwidth. This paper is mainly concerned with directivity and bandwidth enhancement of proximity-coupled microstrip antenna using metamaterial cover. Compared to the patch without metamaterial cover, bandwidth of the antenna is improved about 2.33% and directivity is increased about 9.91dB. The commercial software CST Microwave Studio and a full-wave FDTD numerical technique, developed by the authors, are adopted for the simulations.
Author(s): M. Veysi, A. Jafargholi
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 773 KB

Title: Ultrawide band Negative Refraction Based on Moving Media Concept
Abstract: The anomalous wave propagation in a homogeneous, isotropic and lossless medium that moves with a constant velocity along the axis of a rectangular waveguide; and its interesting properties lead us to the fact that the moving media may be regarded as double negative metamaterial (DNG). In this paper, the correct sign of the permittivity and permeability of an equivalent stationary media, for each TE and TM modes and for both low and high dielectric velocities are investigated and it is shown that this medium acts as a DNG material over specific frequency ranges.
Author(s): A. Jafargholi
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 665 KB

Title: A New Method of QPSK Demodulation Based on Modified 26 GHz Six-Port Circuit
Abstract: In this paper, we propose to study a new demodulation technique of a QPSK signal exploited in a homodyne receiver by using a modified six-port circuit as demodulator. We will present two techniques of the same structure but we will retain only the best configuration. The new approach allows the integration of the receiver module in a high-performance millimeter wave technology, reducing the size and overall cost of the receivers. This approach is validated by using Agilentís Advanced Design System (ADS) software for RF design and simulation.
Author(s): L. Osman, I. Sfar, A. Gharsallah
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 1279 KB

Title: Compact Tri-band Metamaterial Antenna for Wireless Applications
Abstract: A novel compact triband coplanar waveguide fed metamaterial antenna is proposed. The left-handed (LH) inductance is provided by two parallel short ended spiral inductors. We achieved pentamodes of resonance consisting of negative modes, zeroth mode and positive modes. The resonance frequency at each of these modes are f-2=1.01 GHz, f-1=2.11GHz, f0=2.48 GHz, f+1= 3.04 GHz and f+2=3.54GHz with triband functionality obtained at f-2, f0 and f+2 resonances. Gain of the proposed structure at f-2, f0 and f+2 resonances is found to be -3.4993dB, 1.559dB and 1.9515dB respectively. The proposed antenna is measured at Antenna Measurement Facility (AMF) and results were compared with the simulated results. A good agreement between the measured and the simulated results validates the proposed design. The antenna radiates omni-directional waves in the horizontal plane. The proposed antenna serves the criteria for modern multiband wireless applications with an additional feature of increased bandwidth at the zeroth mode. The proposed multiband antenna is suitable for wireless communication applications such as the Global System for Mobile Communications (GSM) 900 in 1.01GHz, Wireless Local Area Network (WLAN) in the 2.48 GHz band (2.459 - 2.4924)GHz of IEEE 802.11b/g ISM band and worldwide interoperability for microwave access (WiMax) standards in the 3.54GHz band (3.491-3.596)GHz of IEEE 802.11a. This proposed antenna is most suitable for precise multiband wireless communication systems which include the mobile and wireless local area network (WLAN) systems due to their large service area.
Author(s): Sheeja K. L., P. K. Sahu, S. K. Behera, N. Dakhli
File Type: Journal Paper
Issue:Volume: 27      Number: 11      Year: 2012
Download Link:Click here to download PDF     File Size: 640 KB