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Title: ACES October 2010 Full Journal
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 12528 KB

Title: ACES October 2010 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 432 KB

Title: Design and Full-Wave Analysis of Cavity-Backed Resistively Loaded Circular-End Bow-Tie Antennas for GPR Applications – Part I
Abstract: In this paper, the design of cavitybacked bow-tie antennas for ground-penetrating radars is presented. Dielectric embedding and resistive loading of the radiating structure are employed to achieve at least 30 : 1 relative bandwidth (55 MHz? >1.5 GHz), with a maximum antenna size of 40 cm and stable antenna performance over different types of the ground. The design procedure is described in detail and provides useful guidelines for the considered class of radiators. Antenna parameters are optimized numerically to combine a large operational bandwidth with reasonably high antenna efficiency. To this end, a full-wave locally conformal finite-difference time domain procedure useful to model electromagnetic structures having complex geometrical and electrical characteristics in the vicinity of the ground is adopted.
Author(s): D. Caratelli, A. Yarovoy
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 2276 KB

Title: Design and Full-Wave Analysis of Cavity-Backed Resistively Loaded Circular-End Bow-Tie Antennas for GPR Applications – Part II
Abstract: In this paper, a comprehensive analysis of a novel GPR antenna featuring almost 30 : 1 relative bandwidth (55 MHz ? >1.5 GHz), with a maximum antenna size of 40 cm is performed. Antenna transient behavior, near-field radiation, and impact of the ground are analyzed in details. It has been shown that the antenna exhibits reduced and short ringing, low spurious energy emission in the air region, as well as stable circuital and radiation properties over different types of soil. Furthermore, the analysis of buried pipe detection using two such antennas has been performed. Novelty of such investigation lies in the fact that at the lowest operational frequency both the receive antenna and buried pipe are situated in the near-field region, whilst at the highest operational frequency only the far field is playing the role. From this analysis, antenna coupling level and waveforms of the target return, which are of crucial importance for GPR system design, are determined.
Author(s): D. Caratelli, A. Yarovoy
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 5952 KB

Title: A Partial Solution of MoM Matrices Based on Characteristic Basis Functions and its Application to On-Board Antennas Positioning
Abstract: A new technique, called incomplete Gauss-Jordan elimination (IGJE), is presented and hybridized with the characteristic basis function method (CBFM) to enable the partial solution of the method of moments (MoM) matrix. As a consequence, the goal of this technique is its application to optimization problems in electrically large scenarios where multiple but similar configurations need to be analyzed, since our method performs these analyses with a considerable reduction in the computational time and also memory. The term “similar” refers to the fact that the original structure is split into different blocks and modifications in the geometry (inserting, eliminating, or changing elements) of only a specific set of these blocks are allowed throughout the optimization process. In particular, we take advantage of this technique to analyze the optimum emplacement of an antenna on a given structure (e.g. a ship or airplane) with just one analysis. An example of an airplane antenna positioning is shown to illustrate the procedure.
Author(s): J. Laviada, J. Gutiérrez-Meana, M. R. Pino, F. Las-Heras
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 894 KB

Title: Strategies for Improving the Use of the Memory Hierarchy in an Implementation of the Modified Equivalent Current Approximation (MECA) Method
Abstract: In this paper, we investigate different techniques for improving the cache memory use when running a parallel implementation of the modified equivalent current approximation (MECA) method. The MECA method allows the analysis of dielectric and lossy geometries, and reduces to the well-studied physical optics (PO) formulation in case of PEC scatterers. We discuss several memory-hierarchy-based optimization techniques and present how to implement them in C. We show through simulations that these optimization strategies are effective for reducing the total execution time when calculating the scattered fields with a parallel implementation of the MECA method.
Author(s): H. Gómez-Sousa, J. A. Martínez-Lorenzo, O. Rubiños-López, J. G. Meana, M. Graña-Varela, N. Gonzalez-Valdes, M. Arias-Acuña
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 360 KB

Title: Analysis of Circular Slots Leaky-Wave Antenna in Cylindrical Waveguide by Wave Concept Iterative Procedure
Abstract: This paper presents the analysis of circular slots leaky-wave antenna by using an iterative method based on the wave concept. The classic method has been reformulated in cylindrical coordinates in order to be adequate for the analysis of the leaky-wave antenna with fast convergence. The proposed leaky-wave antenna can be used to replace a micro-strip patch array. Numerical results are presented to illustrate the advantages of the proposed structure. A good agreement between the new wave concept iterative procedure (WCIP) method results and published data is obtained.
Author(s): Z. Houaneb, H. Zairi, A. Gharsallah, H. Baudrand
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 569 KB

Title: Parasitic Patch of the Same Dimensions Enabled Excellent Performance of Microstrip Antenna Array
Abstract: This paper presents a thorough investigation on the use of parasitic patch as an effective secondary radiator to suppress mutual coupling and improve the gain of a microstrip array. The measured results show that the proposed parasitic patch placed halfway between elements in the E-plane of two-element array not only suppresses mutual coupling by 7.3dB, but, also, improves the gain by 1.6dB. By further simulation and comparison, the results indicate the proposed parasitic patch is quite suitable for application into the high-density microstrip arrays.
Author(s): M. Tang, S. Xiao, T. Deng, D. Wang, B. Wang
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 649 KB

Title: Input Impedance Sensitivity Analysis of Patch Antenna with Discrete Perturbations on Method-of-Moment Grids
Abstract: A new practical approach is proposed to the response sensitivity analysis of highfrequency structures modeled with the method of moments. The response sensitivities are calculated with the self-adjoint approach and discrete shape perturbations on the method of moments grids. The approach requires certain computational effort as a pre-process. This effort is due to building a global system matrix that covers all possible geometrical variations which may arise during design optimization. The technique is illustrated through the sensitivity analysis of the input impedance of a Yagi-Uda array and a printed patch antenna. The computed sensitivities are validated by comparing with the central finitedifference estimates at the response level.
Author(s): Y. Zhang, N. K. Nikolova, M. H. Bakr
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 551 KB

Title: A Microstrip Directional Coupler with Tight Coupling and Relatively Wideband using Defected Ground Structure
Abstract: This paper presents a detailed investigation utilizing a defected ground structure (DGS) to a conventional edge-coupled microstrip coupler with tight coupling level over a relatively wide frequency band. A reasonable spacing between microstrip coupled lines and stronger coupling are achieved using this technique. A 20 dB initial coupler (over a fractional bandwidth of 35% with ?1dB ripple) is converted into 8 dB coupler with almost 3 times wider band by etching off a single unit cell of rectangular and meandered slot loop in the ground plane under the central part of the coupling region. Optimum DGS dimensions are related to coupler dimensions in easy to use design curves. An efficient technique for compensation of the significant unavoidable mismatch resulting from the presence of the DGS is applied and tested. Some coupler samples with different DGS are fabricated, measured, and compared with a conventional coupler counterpart to verify the simulation results and illustrate the improvements, very good agreements are observed.
Author(s): A. S. Al-Zayed, Z. M. Hehjazi, A. S. Mohra
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 1809 KB

Title: Modeling and Simulation of Wilkinson Power Splitter in Suspended Stripline
Abstract: This paper offers one possible solution to the problem of different phase velocities in even and odd mode during the design of Wilkinson power splitters. This topic is especially important in the design of modern beamforming networks for military and space applications where low insertion loss is required and obtained through a use of suspended stripline and other extremely (ultra) inhomogeneous platforms. A new approach is proposed where even and odd mode quarterwave transforming sections of a multi-section Wilkinson splitter do not end at the same locations. The approach has been implemented through an algorithm that calculates all critical parameters of the splitter. In order to confirm the practicality of the proposed solution, various examples of Wilkinson splitters have then been developed through the algorithm and then simulated using SONNET® and other electromagnetic software tools. The developed configurations have, also, been compared to the conventional ones to evaluate the improved performance.
Author(s): S. Ibrahimpasic, M. Hasanovic
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 756 KB

Title: Microwave Detection of Cracks in Buried Pipes using the Complex Frequency Technique
Abstract: This work outlines a new technique for detecting cracks in buried pipes using scattered fields. The matrix pencil method (MPM) is applied on synthetic data to extract the natural frequency poles. A 50 cm long hollow pipe, 2.5 cm in diameter, and 5 mm in thickness is considered. Cracks of arc lengths of 6 cm and 4 cm with a width of 0.5 mm are introduced into the metallic pipes. It is shown that the MPM has the capability to extract distinctive poles associated with these cracks even when the pipe is hidden behind plywood, buried in sand, or when the synthetic data is corrupted with random noise of 10 dB signal to noise ratio.
Author(s): F. Deek, M. El-Shenawee
File Type: Journal Paper
Issue:Volume: 25      Number: 10      Year: 2010
Download Link:Click here to download PDF     File Size: 957 KB