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Title: ACES Journal September 2013 Full Issue
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
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Title: ACES Journal September 2013 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
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Title: Modeling and Analysis of Anechoic Chamber Using CEM Tools
Abstract: Advances in computational resources facilitate anechoic chamber modeling and analysis at VHF/UHF frequencies using full-wave solvers available in commercial software such as FEKO. The measurement community has a substantial and increasing interest in utilizing computational electromagnetic (CEM) tools to minimize the financial and real estate resources required to design and construct a custom anechoic chamber without sacrificing performance. A full-wave simulation analysis such as the finite element method (FEM) provides a more accurate solution than the approximations inherent to asymptotic ray-tracing techniques such as physical optics (PO), which have traditionally been exploited to overcome computational resource limitations. An anechoic chamber is simulated with a rectangular down-range cross-section (in contrast with the traditional square cross-section) to utilize the software’s capability to assess polarization performance. The absorber layout within the anechoic chamber can be optimized using FEKO for minimal reflections and an acceptable axial ratio in the quiet zone. Numerical results of quiet zone disturbances and axial ratios are included for both low- and medium-gain source antennas over a broad frequency range.
Author(s): D. Campbell, G. Gampala, C. J. Reddy, M. Winebrand, J. Aubin
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 889 KB

Title: Study on the Matrix Pencil Method with Application to Predict Time-domain Response of a Reverberation Chamber
Abstract: The full wave simulation of reverberation chamber in time domain usually takes large computational time because of its resonant characteristic. This contribution makes the pioneer exploration of accelerating this kind of simulation by time-domain signal prediction. The prediction technique is based on the well known matrix pencil method (MPM). An approximation to the existing MPM is proposed to obtain a new kind of MPM, which is more computationally efficient. To conduct the prediction effectively, the signal’s oversampling should be avoided and the singular values appeared in MPM should be judged appropriately. The signal can be resampled according to Nyquist sampling law while the singular values can be selected by the newly proposed criterion based on cavity theory. For wideband time-domain responses, it is suggested to apply digital band-pass filter before prediction to get higher precision. Using the proposed methods, the computational time can be reduced almost 50 % for the reverberation chamber’s FDTD simulation.
Author(s): S. Wang, Z. C. Wu, L. Du, G. H. Wei, Y. Z. Cui
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 254 KB

Title: A Shifted SSOR Preconditioner with Low-Rank Compression for Monostatic RCS Calculation
Abstract: Computation time and memory consumption are two crucial bottlenecks for solving large dense complex linear system arising from electric field integral equations (EFIE) formulation of monostatic scattering problems. The traditional symmetric successive overrelaxation (SSOR) preconditioner, derived from the near-field matrix of the EFIE, is widely used to accelerate the convergence rate of iterative solvers. This technique can be greatly improved by modifying the near-field matrix of the EFIE with the principal value term of the magnetic field integral equation (MFIE) operator. Additionally, the adaptive cross approximation (ACA) algorithm is applied to compress the near-field interaction matrix to save memory. Numerical experiment results indicate that the novel technique can significantly reduce both the computational time and memory significantly with low cost for construction and implementation of preconditioners.
Author(s): J. Chen, Z. Liu, B. Yong, Z. Jiang, N. Cao
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 240 KB

Title: An Efficient Hybrid Model in Analyzing Nonlinearly Loaded Dipole Antenna above Lossy Ground in the Frequency Domain
Abstract: In this paper, a hybrid model is proposed for including lossy ground effect on scattering response from nonlinearly loaded dipole antenna. In this model, at first the input admittance and induced current at dipole antenna situated over lossy ground are efficiently modeled based on the fuzzy inference concepts. Volterra series model is then applied to compute the induced voltage across nonlinear load at different frequency harmonics. Numerical examples show not only the accuracy of the proposed hybrid model but also a high computational efficiency in comparison with previous hybrid models.
Author(s): S. R. Ostadzadeh
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 408 KB

Title: Unconditionally-Stable Meshless Methods Using Different Split-Step Techniques and Their Phase Velocity Considerations
Abstract: In this paper, new unconditionallystable meshless methods based on different splitstep methods are proposed. Moreover, comparison of the phase velocities of two different split-step meshless methods and that of alternativedirection- implicit meshless (ADI-ML) method is presented. Here we show how employing splitstep (SS) technique using radial point interpolation meshless (RPIM) method results in an unconditionally stable scheme. Symmetric operators and uniform splitting are utilized simultaneously to split the classical Maxwell’s matrix into four and six submatrices. Also, for more accurate approximations Crank-Nicolson (CN) scheme that is a fully implicit scheme has been applied for implementation of these schemes. It has been demonstrated, these proposed methods produce even more effective unconditionally stable responses than those of alternatingdirection- implicit meshless time-domain ADIMLTD methods. Eventually, in order to prove the advantage of the proposed method, a comparison has been made between these novel meshless methods and their finite-difference counterparts. More smoothed phase velocities in proposed meshless methods imply a reduction in dispersion error in comparison with their analogous cases in finite-difference time-domain (FDTD) method.
Author(s): F. Ansarizadeh, M. Movahhedi
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 354 KB

Title: Adaptive Difference Beam with Low Sidelobes at Subarray Level Based on Semidefinite Programming
Abstract: This paper proposes a semidefinite programming (SDP) method to form adaptive difference beam at subarray level. Its performance is investigated via computer simulations. Compared with loaded sample matrix inversion (LSMI) and constrained adaptive beam-pattern synthesis (CAPS). The proposed algorithm not only has manifest lower sidelobes in quiescent pattern control and sidelobe interference suppression, but also produces more accurate and deeper null in look direction when mainbeam interference deforms the pattern.
Author(s): J. Xu, Y. Zhang, X. F. Shen
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 527 KB

Title: Performance of Vivaldi Antennas in Reflector Feed Applications
Abstract: When a wideband antenna is to be used as a reflector feed, the phase center variation with frequency introduces an error on the phase of the primary field impinging on the reflector surface. This is because the antenna phase center will be coincident with the focus only at one particular frequency and displacement at other frequencies, which will result as the phase error losses due to axial defocusing. Tapered slot antennas are the most utilized antennas in ultra wide band (UWB) high-performance applications. In this work, performance of the UWB Vivaldi antennas (exponentially tapered slot antennas) in reflector feed applications is investigated. A long Vivaldi is designed, manufactured, and its phase center movement with frequency is measured. The correspondent phase error loss is estimated.
Author(s): N. T. Tokan
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 312 KB

Title: A Novel Antenna With Dual Band-Notched Characteristics using Shorting Pin and Z-Shaped Slot on Conductor Backed
Abstract: In this paper, a novel UWB antenna with dual notched bands is presented. The antenna consists of a square patch and a ground plane with a ?-shaped slot, which increase the bandwidth from 2.7 GHz to 11.3 GHz. To achieve two bands stop, both Z-shaped slot on conductor backed plane and strip ended up a shorting pin are used. The designed antenna has a small size of 15 × 22 mm2 while indicating the band-stop performance in the frequency bands of 3.1 GHz to 3.8 GHz and 5.1 GHz to 6.1 GHz in order.
Author(s): M. Khodaee, M. Akbari, S. Zarbakhsh
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 520 KB

Title: CPW-Fed Slot-Like Sleeve-Monopole Antenna with Bandwidth Enhancement for UWB Wireless Communications
Abstract: This paper proposes a novel slot-like sleeve-monopole antenna for ultra wideband applications with multi-resonances performance. The antenna consists of a CPW-fed sleeve monopole antenna with a coupled inverted Ushaped strip, surrounded by a pair of folded strips, which provides a wide usable fractional bandwidth of more than 120 % (3.09 GHz - 12.86 GHz). By adding a coupled inverted U-shaped strip with variable dimensions on the radiating patch and also by inserting two folded strips, additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the higher band. The designed antenna has a small size of 30 × 30 mm2 . Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.
Author(s): S. Bashiri, Ch. Ghobadi, J. Nourinia, M. Ojaroudi
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 456 KB

Title: A Novel Ultra-wideband Planar Antenna with Rejection of WLAN and ITU Bands
Abstract: A novel compact coplanar waveguidefed ultra wideband (UWB) antenna is proposed with dual band-notched characteristics. The antenna consists of novel tapered patch and is printed on FR4 substrate with compact size of 18 ? 23 mm2. By inserting a novel parasitic strip in trapezoidal slot and a pair of L-shaped slots in metallic ground, dual band-notched characteristics are obtained. Parametric analysis is performed by studying the effects of geometrical parameters of antenna on various characteristics. The antenna operates from 3.1 GHz to 11.6 GHz with dualnotched bands of 5.1 GHz-6.2 GHz and 8 GHz-8.4 GHz to avoid potential interference from WLAN and ITU bands, respectively. The antenna is analyzed in both frequency and time domains. The measured results show that the antenna has stable radiation patterns, consistent gain over the entire operating band. The time domain group delay of antenna indicates good linear phase response. The main features that make the antenna suitable for UWB applications are compactness, simple configuration, and stable radiation patterns.
Author(s): A. Subbarao, S. Raghavan
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 362 KB

Title: Omni-Directional/Multi-Resonance CPW-Fed Small Slot Antenna for UWB Applications
Abstract: In this paper, a novel multi-resonance small slot antenna with CPW feed-line and square radiating stub, for UWB applications is proposed. The proposed antenna consists of a square radiating stub with an inverted T-shaped slot and a ground plane with a T-shaped slit, which provides a wide usable fractional bandwidth of more than 145 % (1.89 GHz ? 12.43 GHz). By cutting a Tshaped slit with variable dimensions on the ground plane, and an inverted T-shaped slot in the square radiating stub additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the lower and upper bands. The proposed antenna displays a good omni-directional radiation pattern even at higher frequencies. The designed antenna has a small size of 30×30 mm2. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.
Author(s): A. Kamalvand, Ch. Ghobadi, J. Nourinia, M. Ojaroudi, N. Ojaroudi
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 387 KB

Title: Antenna Selection Procedure for BTS Over HAPs
Abstract: table antenna for a GSM urban macro cell covered by a base transceiver station (BTS) mounted on high altitude platform (HAP) at the stratosphere layer. To this end, an ideal cosine shape radiation pattern raised to the power of N is applied to select the appropriate antenna for achieving the optimum coverage. The optimum selection is based on minimizing the blind area, having less overlapped to total area ratio, and increasing the total coverage area, simultaneously. Our proposed scheme has two degrees of freedom; first, the values of N determining the directivity and half power beam width (HPBW), and second the angle ? denoting to the mechanical tilt of the antenna elements. To find the optimum pair of (N, ?), several simulations are done and the corresponding footprint contours are depicted. Simulation results show that utilizing three ideal cosine function antennas with N = 9 installed by ? = 38 degrees of mechanical tilt with respect to the normal is optimum for a macro cell coverage in an urban area by using HAPs located at 17 km altitude.
Author(s): A. Araghi, M. Mayiami, A. Montazeri, A. Foudazi, M. Yaghubi, M. Bod
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 367 KB

Title: Compact Oscillator Feedback Active Integrated Antenna by Using Interdigital Coupling Strip for WiMAX Applications
Abstract: A novel active feedback antenna for WiMAX applications is presented. By using an interdigital coupling strip in the active feedback antenna two new resonances can be achieved. Also the proposed interdigital radiating patch has a major advantage in providing tighter capacitive coupling to the line in comparison to known radiating patch. In order to generate DC isolation in the RF path, we use a pair of gap distances in the microstrip loop. Simulated and experimental results obtained for this antenna show that the proposed active integrated antenna (AIA) has a good return loss and radiation behavior within the WiMAX frequency range.
Author(s): J. Mazloum, A. Jalali, M. Ojaroudi, N. Ojaroudi
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 419 KB

Title: Design and Analysis of The Stub and Radial-Stub Loaded Resonator Band-Pass Filter with Cross-Shaped Coupled Feed-Lines for UWB Applications
Abstract: In this paper, the procedure of attaining a compact microstrip ultra-wideband (UWB) band-pass filter (BPF) by the use of stub and radial stub loaded resonator and also cross-shaped coupled lines (CCLs) as feed-lines, is presented and discussed. Implementation of CCLs results in suppression of the unwanted pass-band harmonics while by loading the resonator, additional transmission zeros (TZs) are produced, which lead to improvement of the in-band performance of the BPF. Measurement results of the fabricated UWB BPF are in good agreement with simulation predictions and the presented BPF has a sharp rolloff and improved out-of-band performance in the frequency band of interest.
Author(s): B. Mohammadi, J. Nourinia, Ch. Ghobadi, A. Valizade
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 471 KB

Title: Characteristic Parameters Determination of Different Striplines Configurations using HBEM
Abstract: Different configurations of striplines are analyzed using the hybrid boundary element (HBEM) method, developed at the Faculty of Electronic Engineering of Niš. The quasi TEM analysis is applied. The effective dielectric permittivity as well as the characteristic impedance of several 2D striplines are determined. In order to validate the obtained HBEM values of the characteristic impedance, in terms of accuracy, they have been compared with the corresponding ones obtained by the finite element method. Fast convergence of the results, short computation time, and possibility to solve complex multilayered configurations of striplines, make hybrid boundary element method very efficient in the calculation of 2D striplines parameters. All results are presented in tables and graphically.
Author(s): M. T. Peric, S. S. Ilic, S. R. Aleksic, N. B. Raicevic
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 383 KB

Title: Compact Branch Line Coupler using Step Impedance Transmission Lines (SITLs)
Abstract: A compact branch line coupler is proposed by using the optimized step impedance transmission lines (SITLs). The proposed branch line coupler has an area reduction of more than 50% at 1 GHz. The measured results of the fabricated coupler are in good agreement with the simulation results.
Author(s): S. H. Sedighy, M. Khalaj-Amirhosseini
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 253 KB

Title: An Adaptive Time-Stepping Algorithm in Weakly Coupled Electromagnetics-Thermal-Circuit Modeling
Abstract: This paper presents a weakly coupled formulation for the electromagnetic and thermal fields by applying the backward differentiation formula (BDF) and the Theta algorithm for the adaptive time-stepping and variable order 2D finite-element discretization. A coupling of the electromagnetic diffusion equation (EDE) and the electrical circuit equations is also included. A minimum time step criterion is adopted and an algorithm for the time-step size and order selection is implemented. The proposed model was programmed in C language. An example is presented to show the application of the formulation.
Author(s): R. B. B. Ovando-Martinez, C. Hernandez, M. A. Arjona
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 646 KB

Title: Electromagnetic Analysis of a Novel Cylindrical Transverse-Flux Permanent-Magnet Linear Machine
Abstract: Cylindrical transverse-flux permanentmagnet linear machine (TFPMLM) is a novel electric machine used for free piston energy converters. As the disadvantages of low power factor and complex manufacture exist in the conventional TFPMLM, this paper employs the staggered (not overlapped) stator teeth to reduce the flux leakage, and further increase the power factor and force density. In this paper the flux leakage and performances of two topologies are researched and compared. Then thorough analysis is made on axial 3-phase TFPMLM, which has great potential in force density and power factor. Thrust fluctuation, force density and power factor of the axial TFPMLM are analyzed. Moreover, the methods to improve force density and power factor are researched. Finally, a scheme with power factor up to 0.52, force density up to 2.17×105N/m3 is developed.
Author(s): P. Zheng, B. Yu, H. Yan, Y. Sui, J. Bai, P. Wang
File Type: Journal Paper
Issue:Volume: 28      Number: 9      Year: 2013
Download Link:Click here to download PDF     File Size: 531 KB