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Title: ACES Journal December 2013 Full Issue
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
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Title: ACES Journal December 2013 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 55 KB

Title: Characterization of Biaxial Materials Using a Partially-Filled Rectangular Waveguide
Abstract: A technique is proposed to measure the permittivity and permeability parameters of a sample of biaxial material placed into a rectangular waveguide. By constructing the material as a cube, only a single sample is required to find all six material parameters. The sample is inserted into the waveguide in multiple orientations, and the transmission and reflection coefficients of the sample region are measured using a vector network analyzer. The material parameters are then found by equating the measured S-parameters to those determined theoretically using a mode-matching technique. The theoretical details are outlined and the extraction process is described. A stacked dielectric cube is characterized experimentally to demonstrate the feasibility of the approach, and results are compared to those obtained using a reduced-aperture waveguide technique.
Author(s): J. Tang, B. Crowgey, O. Tuncer, E. Rothwell, B. Shanker, L. Kempel, M. Havrilla
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
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Title: Wideband Measurements of the Forward RCS and the Extinction Cross Section
Abstract: This paper describes the development of a method based on measurements of the radar cross section (RCS) amplitude and phase in the forward direction to determine the extinction cross section for the 2.5 GHz - 38 GHz frequency range using the optical theorem. Forward RCS measurements are technically complicated due to that the direct signal has to be subtracted from the total signal at the receiving antenna in order to extract the forward RCS. The efficiency of this subtraction as a function of time is evaluated. A traditional calibration method using a calibration target and a second method that does not require a calibration target are investigated and compared. The accuracy of the forward RCS measurements is determined using small spheres of different sizes. The spheres have a forward RCS that is straight forward to calculate with good accuracy. The method is also extended to polarimetric measurements on a small helix that are compared with method-of-moments calculations to validate the method.
Author(s): C. Larsson, M. Gustafsson
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 2451 KB

Title: A Three Dimensional FDTD Algorithm for Wave Propagation in Cold Plasma Media using Forth-Order Schemes
Abstract: A fourth-order accurate in space and second-order accurate in time, finite-difference time-domain (FDTD) scheme for wave propagation in cold plasma media is presented. The formulation of Maxwell’s equations is fully described and an elaborate study of the stability and dispersion properties of the resulting algorithm is conducted. The efficiency of the proposed FDTD (2, 4) technique in cold plasma media compared to its conventional FDTD (2, 2) counterpart is demonstrated through numerical results.
Author(s): M. Pourbagher, S. Sohafi
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 493 KB

Title: A Cone Shaped Tapered Chamber for Antenna Measurements Both in Near Field and Far Field in the 200 MHz to 18 GHz Frequency Range and Extension of the Quiet Zone using an RF Lens
Abstract: Traditionally, tapered chambers are constructed using a square based pyramidal shaped taper. The taper is then shaped into an octagon and finally transformed into a cylindrical launch section. This approach is related to the manufacturability of different absorber cuts. This paper introduces a chamber where the conical shape of the launch in continued throughout the entire length of the tapered chamber. The results of the free space VSWR test over a 1.5 m diameter quiet zone (QZ) are presented at different frequencies. The conical taper appears to have a better illumination wave front and better QZ levels even at frequencies above 2 GHz than the standard traditional approach. This design was implemented in Singapore and the actual chamber was designed to have a secondary near field range for planar and spherical scans. As with all antenna chambers, as the frequency increases, the usable or far field illuminated QZ is reduced. At a 12 m distance from the feed to the turntable, the quiet zone at 8 GHz is reduced to 45 cm. The chamber includes a near to far field range to allow the use of the chamber at higher frequencies when testing electrically large antennas. Another solution implemented to extend the quiet zone at high frequency is to use a large dielectric lens to improve the phase distribution of the field. A light weight, broadband lens with a diameter of 2 m was developed by Matsing Pte Ltd. The parameters of the lens were specially customized for the tapered chamber built. The RF lens, weighing just 35 kg, has a focal length of 10 m. It was installed in front of the turn table. The performance of the tapered chamber with the RF lens is presented. The usable far field QZ was increased by using a dielectric RF lens that allows for electrically larger antennas to be measured in the tapered range of the chamber.
Author(s): V. Rodriguez, S. Matitsine, T. T. Chia, P. Lagoiski, L. Matytsine, M. Matytsine, P. K. Tan
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 1254 KB

Title: A Model-Based Technique with l1 Minimization for Defect Detection and RCS Interpolation from Limited Data
Abstract: Method of moments (MoM) codes have become increasingly capable and accurate for predicting the radiation and scattering from structures with dimensions up to several tens of wavelengths. In an earlier work, we presented a network model (NM) algorithm that uses a Gauss- Newton iterative nonlinear estimation method in conjunction with a CARLOS-3D™ MoM model to estimate the “as-built” materials parameters of a target from a set of backscatter measurements. In this paper, we demonstrate how the NM algorithm, combined with the basis pursuits (BP) ?1 minimization technique, can be used to locate unknown defects (dents, cracks, etc.) on a target from a limited set of RCS pattern measurements. The advantage of ?1 minimization techniques such as BP is that they are capable of finding sparse solutions to underdetermined problems. As such, they reduce the requirement for a priori information regarding the location of the defects and do not require Nyquist sampling of the input pattern measurements. We will also show how the BP solutions can be used to interpolate RCS pattern data that is under sampled or has gaps.
Author(s): I. J. LaHaie, S. M. Cossmann, M. A. Blischke
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 15058 KB

Title: A Statistical Assessment of the Performance of FSV
Abstract: This paper assesses the performance of the feature selective validation (FSV) method by applying probability density functions to the FSV point-by-point analysis. As an augmentation to confidence histograms, probability density functions offer two advantages: they (1) provide the users of FSV with more subtle information about the quality of the data comparison and (2) make a statistical analysis of the FSV results available. The application of probability density functions in the verification of FSV is presented in this paper, which provides a quantitative measure to support the qualitative conclusions drawn in early publications on the FSV method used as a foundation for IEEE Std. 1597.1.
Author(s): G. Zhang, H. Sasse, L. Wang, A. Duffy
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 609 KB

Title: Fast Multipole Method for Large-Scale Electromagnetic Scattering Problems on GPU Cluster and FPGA-Accelerated Platforms
Abstract: The fast multipole method (FMM) for large-scale electromagnetic scattering problems is implemented on high performance computing (HPC) platforms and its performance is investigated in terms of accuracy, speedup, and scalability. The HPC platforms include a 13-node graphical processing unit (GPU) cluster, and a field programmable gate array (FPGA)-based high performance reconfigurable computer (HPRC). The details of the implementations and the performance achievements are shown and analyzed. We demonstrate a scalable parallelization while maintaining a good degree of accuracy.
Author(s): V. Dang, Q. Nguyen, O. Kilic
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 831 KB

Title: Computer Reconstructed Holographic Technique for Phase-less Near-Field Measurement
Abstract: A novel holographic near-field phaseless technique is presented. The measurement system is composed of the antenna under test, the reference antenna, the amplitude scanning measurement system, and the holographic reconstructed algorithm. The interference amplitude of the antenna under test with the reference antenna is measured by the amplitude scanning system. The complex near field of the antenna under test is reconstructed by a computer, where the measured interference is corrected by the multiplication with the virtual spherical reference wave and then filtered in Fourier transformation domain (e.g., plane wave angular spectrum) or the back-projected image space. The reconstruction method is rigorous without traditional Fresnel approximation. The novel technique requires the amplitude on one measurement surface and the computer reconstructed algorithm, while the previous phase less technique depends on two measurement surfaces or extra hardware to provide synthesizedreference- wave. The novel measurement method and reconstruction algorithm could be used in many applications as for the planar near field measurement for example. Simulated results are presented to demonstrate the complex field retrieval method and near-field to far field transformation.
Author(s): L. Zhiping, Z. Wang, W. Jianhua
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 347 KB

Title: VFD Approach to the Computation TE and TM Modes in Elliptic Waveguide on TM Grid
Abstract: We describe here a vector finite difference approach (VFD) to the evaluation of eigenvalues and modes of elliptical waveguides. The FD is applied using a 2D elliptical grid in the waveguide section. A suitable Taylor expansion of the vector mode function allows to take exactly into account the boundary condition. To prevent the raising of spurious modes, our FD approximation results in a constrained eigenvalue problem, that we solve using a decomposition method. This approach has been evaluated comparing our results to known data for the elliptic case.
Author(s): A. Fanti, G. Montisci, G. Mazzarella, G. A. Casula
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 515 KB

Title: A Thin Dielectric Approximation for Calculation of Electromagnetic Scattering from 3-D Homogeneous Chiral Bodies
Abstract: The full current thin dielectric sheet (TDS) approximation is considered for the problem of electromagnetic (EM) scattering by a three-dimensional (3-D) homogeneous thin chiral dielectric sheet. This approximation leads to surface integral equations (SIE) instead of the traditional volume integral equations (VIE). The surface of the thin dielectric region is modeled by triangle cells. Consequently, the number of unknowns is reduced by only surface meshes being utilized to discretize the dielectric geometry. Modified Rao-Wilson-Glisson (RWG) and pulse functions simultaneously for basis and testing functions are employed to approximate the tangential and normal currents in the dielectric layer. Then these SIEs are solved numerically using the conventional method of moments (MoM). The results by this approach show agreement with other methods while it greatly reduces the number of unknowns.
Author(s): X. Deng, Y. Tian, J. Wang, C. Gu, Y. Zhou
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 391 KB

Title: Novel Monolayer Windmill Structure Left-Handed Metamaterial
Abstract: In this paper, a simple structure made of periodic arrays of windmill structure, printed on only one side of a dielectric substrate, is introduced. Simulation and measurement were carried out for one layer of infinite left-handed material (LHM) slab using monolayer windmill structure. The results showed that by carefully adjusting the dimensions of the windmill structure, magnetic and electric resonances can be coexistent in a frequency range where there are both negative magnetic and electric responses. To further verify the left-handed (LH) properties of this structure metamaterial, effective medium parameters were retrieved and a refraction phenomenon based on a wedge-shaped model was demonstrated. Equivalent circuits for the magnetic and electric resonance were also offered to give a qualitative explanation of the LH behaviours.
Author(s): H. Xiong, J. S. Hong, D. L Jin
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 599 KB

Title: Measurements on Long and Rigid Objects for Radar Field Probe
Abstract: As a novel concept for field probes, radar cross section (RCS) measurements on long rigid objects rotated within a small angular range in and out of the broadside condition are reported. The rotation was maintained either in a horizontal (H) plane or in a vertical (V) plane containing the center of the quiet-zone (QZ). Processing the RCS data by DFT yields a spectrum, which is recognized as the field distribution along that object. This spectrum compares extremely well to traditional field-probes taken earlier by translating a sphere across the QZ in H- or V-direction. Preliminary results at several S-band frequencies are presented and discussed.
Author(s): P. S. P. Wei
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 931 KB

Title: Planar Metamaterial for Matched Waveguide Termination
Abstract: We present the design, fabrication, and characterization of a novel matched waveguide termination based on planar artificial metamaterial. This matched termination is realized by recent developed planar metamaterial absorber, which can be designed to near-completely absorb the propagating electromagnetic energy at the edge of a shorted rectangular waveguide. Theoretical discussions, numerical simulations and microwave experiments are employed to illustrate the matched characteristics of the proposed waveguide termination. As an example, a matched waveguide termination with standing wave ratio of 1.23 is experimentally demonstrated at microwave frequency. Our result yields a promising approach to design of novel waveguide terminations by techniques of metamaterials.
Author(s): J. Li, F. Wang, G. Wen, Y. Huang, W. Zhu
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 458 KB

Title: UWB Monopole Antenna with WLAN Frequency Band-Notched Performance by using a Pair of E-Shaped Slits
Abstract: In this paper an ultra-wideband monopole antenna with frequency band-stop performance is designed and manufactured. The proposed antenna consists of square radiating patch with two E-shaped slits and a ground plane with a protruded T-shaped strip inside the rectangular slot. In the proposed structure, by inserting a rectangular slot with a T-shaped strip protruded inside the slot on the ground plane, additional resonance is excited and hence, much wider impedance bandwidth can be produced, especially at the higher band. In order to create band-rejected function we use two E-shaped slits in the square radiating patch. The fabricated antenna has the frequency band of 3 GHz to over 12.7 GHz with a rejection band around 5 GHz – 6 GHz. Good VSWR and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for UWB applications
Author(s): N. Ojaroudi, M. Ojaroudi, N. Ghadimi
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 403 KB

Title: Design of an Array Feed Offset Parabolic Reflector Antenna by Using Electromagnetic Simulations and Measured Results
Abstract: Offset parabolic reflector antennas are well-known for their very simple configurations and are widely used. However, low antenna gain sometimes results in inconvenient operation. In order to increase the antenna gain, an array feed is generally employed to correct the antenna aperture distribution. However, accurate and low-loss realization methods for array feeds were not studied sufficiently. In this work, radiation pattern synthesis is first performed at the array feed to achieve uniform aperture distribution. As a result of this synthesis, the array excitation coefficients are determined. Further, accurate design methods for corporate feed line networks to obtain the required excitation coefficients and low feeder loss through electromagnetic simulations are described. Finally, the designed array feed is fabricated, and the measured radiation patterns are compared with the calculated results. Moreover, the array feed is combined with the fabricated offset reflector, and the antenna radiation patterns and gains are obtained. An increase in the antenna gain is ensured.
Author(s): N. Michishita, J. Shinohara, Y. Yamada, M. T. Islam, N. Misran
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 723 KB

Title: UWB Slot Antenna with Band-Stop Operation by Using H-Shaped Parasitic Structures for UWB Applications
Abstract: A novel ultra wideband (UWB) printed slot antenna with band-notched performance is designed and manufactured. In order to increase the impedance bandwidth of the slot antenna, we use a rectangular slot with an H-shaped parasitic structure inside the rectangular slot on the feedline that with this structure UWB frequency range can be achieved. Additionally, by using a square ring radiating stub with a rotated H-shaped parasitic structure inside the square ring, a frequency band-stop performance has been obtained. The designed antenna has a small size of 20 × 20 mm2 while showing the radiation performance in the frequency band of 2.97 GHz to over 12.39 GHz with a band rejection performance in the frequency band of 5.01 GHz to 5.98 GHz. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.
Author(s): M. Ojaroudi, N. Ojaroudi, N. Ghadimi
File Type: Journal Paper
Issue:Volume: 28      Number: 12      Year: 2013
Download Link:Click here to download PDF     File Size: 448 KB