ACES Publication Search
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| Title: | ACES Journal June 2017 Cover |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 2125 KB |
| Title: | ACES Journal June 2017 Front/Back Matter |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 128 KB |
| Title: | ACES Journal June 2017 Full |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 9830 KB |
| Title: | Analysis of Truncated Gratings and a Novel Technique for Extrapolating their Characteristics to those of Infinite Gratings |
| Abstract: | Periodic gratings, such as Frequency Selective Surfaces (FSSs) and EBG (electromagnetic band gap) structures, are used in a wide variety of electromagnetic applications and are typically analyzed under the assumption that they are infinite periodic. Since the real-word structures are necessarily finite, and are derived by truncating the corresponding infinite structures, it is of interest to determine how large the finite structure needs to be so that it mimics its infinite counterpart. A related question is how to extrapolate the simulation results of a finite structure to predict the performance of the corresponding infinite structure in a computationally efficient manner. The objectives of this work are to address both of these questions and to present a novel computational technique which hybridizes analytical and numerical techniques to provide the answers. We illustrate the application of the proposed technique by considering the test case of plane wave scattering by a strip grating and investigate the asymptotic behavior of the solution for the current on a truncated periodic grating as we increase its size. The proportionality constant, relating the current distribution on the unit cell of the infinite grating to the corresponding distribution in the truncated grating, is computed, and its asymptotic value is accurately predicted by using an extrapolation algorithm presented in the paper. The required number of strips is estimated such that the current on the finite structure is sufficiently close to that on the infinite one. The results obtained for the current are found to be in excellent agreement with those derived from full-wave simulations. |
| Author(s): | N. L. Tsitsas, R. Mittra |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1836 KB |
| Title: | Comparisons Among EIT Data Collection Techniques and Reconstruction Algorithms |
| Abstract: | Electrical Impedance Tomography (EIT) is an imaging technique that aims to reconstruct the spatial electrical conductivity distribution in sections of the human body. In this paper, in order to solve the EIT forward and inverse problems, a finite difference approach to the solution of Maxwell’s equations and the Newton- Raphson algorithm have been employed, respectively. In particular, the inverse problem has been solved using the Tikhonov regularization with various choices of the regularization matrix. Moreover, different data collection methods have been tested on simulated measurements. The obtained results have been compared based on the average deviation of the estimated conductivity distribution with respect to the reference one. The reconstruction procedure has been validated through a comparison with the EIDORS open source software. The best image reconstruction has been obtained by using the neighboring data collection method with null regularization matrix, and using the truncated singular value decomposition to perform the matrix inversion. Moreover, the cross and opposite data collection methods showed better performance than the neighboring one in the presence of a random noise added to the measured signal, while the opposite method evidenced the best results with respect to electrode positioning uncertainties. |
| Author(s): | S. Pisa, E. Pittella, E. Piuzzi |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1846 KB |
| Title: | Optimal Design of Electromagnetic Devices Using the League Championship Algorithm |
| Abstract: | Nowadays, there is an increasing attention on novel metaheuristics and their applications in different problems of science and engineering. A new efficient optimization method, called the League Championship Algorithm (LCA) is applied in this paper for the optimal design of electromagnetic devices. This method is inspired by the competition of sport teams in an artificial sport league for several weeks and over a number of seasons. The performance of the proposed algorithm is tested against two benchmark problems: the magnetizer and the outrunner-type brushless DC motor. The obtained results show that the LCA is an efficient and competitive algorithm for constructing optimal design of electromagnetic devices. |
| Author(s): | H. R. E. H. Bouchekara, M. Nahas, H. M. Kaouach |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1889 KB |
| Title: | Effective Medium Model for Multilayered Anisotropic Media with Different Orientations |
| Abstract: | An efficient model is developed to simulate multilayered biaxial anisotropic material with different orientations by using effective medium theory. Equivalent model is used to extract effective permittivity, permeability and orientation angle for multilayered biaxial anisotropic medium. Analytical expressions for effective parameters and orientation angle are derived for low frequency (LF) limit. The model also gives a non-magnetic effective anisotropic layer if each layer is non-magnetic anisotropic dielectric. Good agreement is achieved by comparing the effective parameters extracted with and without low frequency approximation. We show that the frequency-independent equivalent model is valid for frequency up to 10 GHz. |
| Author(s): | Y. Bao, J. Song |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1907 KB |
| Title: | Effects of Room Dimensions on the Frequency Response of Indoor Wave Propagation |
| Abstract: | In analogy with room acoustics, various aspects of microwave propagation in a room are treated. This paper presents the effect of the room dimensions on the frequency response of a propagating wave inside rooms. It is found by simulation and measurements that room dimensions affect the propagating waves in the rooms and degenerated bands can appear. In critical environments this may cause unwanted coloration effects, which decrease the signal quality. Appropriate choice of room dimensions may reduce the coloration effects of modes. A numerical optimization technique implemented in FEKO software package is used for finding the optimum room dimensions as to achieve the flattest possible frequency response. The effect of the room dimensions on wave propagating in corridors is presented. It is found that the room length has more effects on the frequency response of the signal than the room width for signals excited and transmitted in corridors. |
| Author(s): | H. M. El-Maghrabi, A. M. Attiya, E. A. Hashish |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1762 KB |
| Title: | SIW Rotman Lens with Planar Slot Array Antenna at Ku-band |
| Abstract: | A multi-beam antenna, which is the combination of a Rotman lens and a planar slot array antenna, is designed in this paper. The lens and the slot array are designed for 15.5 to 16.5 GHz frequency range and implemented in the same substrate using SIW structure. The Rotman lens with 7 input ports and 7 output ports are connected to a planar slotted array antenna with 7 waveguides. This multi-beam antenna consists of seven beams at angles of 0°, ±10°, ±20° and ±30° symmetrically. This antenna is designed for terrestrial and satellite applications, where the low cost, low profile and light multi-beam antennas are needed. Simulated and measured results show that the amplitude and phase distributions and scattering parameters of the antenna are in good agreement. In addition, the SLL, HPBW, main beam direction and cross polarization levels of all the radiation patterns are desirable. |
| Author(s): | S. A. Hosseini, Z. H. Firouzeh, M. Maddahali |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 2116 KB |
| Title: | Improvement of the Broadside Radiation Pattern of a Conformal Antenna Array using Amplitude Tapering |
| Abstract: | In this paper, an algorithm for evaluation of near optimal amplitude excitation coefficients for a conformal array on a wedge-shaped surface has been developed in order to maximize the broadside radiation pattern. The radiation pattern for an eight-element conformal antenna has been analyzed and the derived analytical expressions are used to recover the distorted broadside radiation pattern. A heuristic amplitude tapering algorithm is developed to maximize the broadside radiation pattern through the control of individual voltage variable attenuator of each radiating element in the array. It is shown that with appropriate amplitude tapering, the broadside radiation pattern of the array can be improved without phase correction. The pattern recovery information is used to develop a new 1 x 8 microstrip patch antenna array bent at certain angles on a single curved non-conducting structure and the measured results are shown to agree well with the analytical solutions. |
| Author(s): | Irfanullah, S. Khattak, B. D. Braaten |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1645 KB |
| Title: | Electromagnetic Time-Reversal Imaging Using Grouped Sub-Arrays for Resolution Enhancements |
| Abstract: | A new time-reversal (TR) imaging method using grouped sub-arrays for resolution enhancements is presented in this work. The method gives the image of the searching space for each target or scattering center at its own optimum instant, in contrast to the traditional TR imaging method that shows a snapshot of the whole domain at a specified instant. By introducing a grouping scheme that divides the time-reversal mirror (TRM) as many sub-TRMs, resolution enhancements in both crossrange and co-range directions are realized by means of destructive multiplication and incoherent superposition of the normalized sub-TRM imaging signals at nontarget positions. The present method permits all targets or scattering centers to be rendered at equal visibility, and has no requirement on the number of transmitters. Several simulation examples are provided to examine the performance of the proposed method. |
| Author(s): | Y.-Q. Li, X.-Q. Zhang, M.-Y. Xia |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1984 KB |
| Title: | Ultra-wideband and Polarization-insensitive RCS Reduction of Microstrip Antenna using Polarization Conversion Metasurface |
| Abstract: | A new type of polarization conversion metasurface (PCM) is presented to reduce radar cross section (RCS) of microstrip antenna. The proposed PCM consists of evolved split ring (ESR) resonators. Through designing of the PCM unit cell with five resonances and symmetrical layout, a high polarization conversion ratio and ultra-wideband passive cancellation are achieved. The proposed antenna (with PCM) and a reference antenna are designed, simulated and measured. The measured results show that our proposed antenna can achieve 10 dB in-band and 5 dB out-of-band RCS reduction in an ultra-wide frequency band from 6 GHz to 26.7 GHz. Moreover, the PCM works efficiently for both x- and y-polarized incident waves. The measured results show a good agreement with the simulations. Compared to previous researches, the proposed PCM features a compact profile and wider operating bandwidth of RCS reduction. |
| Author(s): | J. Su, C. Kong, Z. Li, X. Yuan, Y. L. Yang |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 2304 KB |
| Title: | Electromagnetic Modelling of Bundle of Single-walled Carbon Nanotubes with Circular Geometry for Antenna Applications |
| Abstract: | This paper aims to present an effective electromagnetic (EM) modelling approach for circular bundle of single-walled carbon nanotubes (CBSWCNTs), based on the electrical conductivity, relative complex permittivity and linear distribution impedance by applying General Ohm’s law for this bundle. The equivalent single conductor material (ESCM) model for personification the CB-SWCNTs is presented in this paper. The main target of this modelling approach is to estimate and investigate the EM properties of CBSWCNTs using common EM engineering tool solver CST (MWS). For this purpose, the CB-SWCNTs and ESCM dipole antennas will be designed and implemented using CST (MWS). Mathematically, the equivalent conductivity model, relative complex permittivity and other parameters of the CB-SWCNTs will be derived in this paper and considered as equivalent material parameters for the ESCM. This modelling technique is expected to provide new avenues for designing different antenna structures. |
| Author(s): | Y. N. Jurn, M. Abdulmalek, H. A. Rahim, S. A. Mahmood, W.-W. Liu |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1541 KB |
| Title: | K-band Planar and Low-profile Fabry-Perot Cavity Antenna with a Coupled Strip-Slitline Feed Structure |
| Abstract: | In this paper, a design of a planar, lowprofile, and high gain Fabry-Perot cavity antenna for Kband applications is presented. The antenna is consisted of a frequency selective surface (FSS) made of a circular hole array and a feeding structure made of a coupled strip-slitline. The FSS and the slitline both are lithographically patterned on a high permittivity substrate while the stripline is printed on top of a thin and low permittivity substrate. These two substrates are then closely appressed each other to form a planar structure. The measured results show that the proposed antenna has an impedance bandwidth of about 4% (|S11|?-10 dB), a maximum gain of about 10.4 dBi, and a 3-dB gain bandwidth of approximately 2.9% at the resonance frequency of around 20.8 GHz. The antenna’s compact, planar, and lightweight profile, i.e., approximately 4?o × 4?o × 0.24?o of a free-space wavelength at 21.0 GHz makes it promising for a small and efficient source in K-band applications. |
| Author(s): | H. H. Tran, T. K. Nguyen |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 2166 KB |
| Title: | Design and Analysis of a Koch Snowflake Fractal Monopole Antenna for Wideband Communication |
| Abstract: | In this article a compact wideband monopole antenna with constant high gain has been designed and fabricated for wideband microwave communication. Koch fractal geometry has been applied for design of this antenna structure. A wide bandwidth of 3.3 GHz (3.0 GHz to 6.3 GHz) has been obtained, which covers the IEEE 802.11 WLAN bands (5.2 GHz and 5.8 GHz) and WiMAX bands (3.5 GHz and 5.5 GHz). The proposed antenna is characterized by its high gain which remains constant throughout the entire operation bandwidth. An average gain of 5.07 dBi has been realized at all the frequencies of interest. The realized antenna gains are 5.01 dBi, 5.07 dBi, 5.09 dBi and 5.11 dBi at frequencies of 3.5 GHz, 5.2 GHz, 5.5 GHz and 5.8 GHz respectively. Good agreement between simulated and measured results justifies the applicability of the proposed antenna for wideband communication purpose, particularly for the WLAN and WiMAX microwave frequency bands of interest. |
| Author(s): | A. Bhattacharya, B. Roy, S. K. Chowdhury, A. K. Bhattacharjee |
| File Type: | Journal Paper |
| Issue: | Volume: 32 Number: 6 Year: 2017 |
| Download Link: | Click here to download PDF File Size: 1890 KB |