International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. A Review of Computational Electromagnetic Methods for Graphene Modeling Sat, 30 Apr 2016 11:28:35 +0000 http://www.hindawi.com/journals/ijap/2016/7478621/ Graphene is a very promising optoelectronic material and has gained more and more attention. To analyze its electromagnetic properties, several numerical methods have been developed for graphene simulation. In this paper, a review of application of graphene in electronic and photonic device is provided, as well as some widely used computational electromagnetic algorithms for graphene modeling. The advantages and drawbacks of each method are discussed and numerical examples of these methods are given to illustrate their performance and application. Yu Shao, Jing Jing Yang, and Ming Huang Copyright © 2016 Yu Shao et al. All rights reserved. Through-Wall Detection with LS-SVM under Unknown Wall Characteristics Thu, 28 Apr 2016 11:44:24 +0000 http://www.hindawi.com/journals/ijap/2016/2790782/ One of the main challenges in through-wall imaging (TWI) is the presence of the walls, whose returns tend to obscure the target behind the walls and must be considered and computed in the imaging procedure. In this paper, a two-step procedure for the through-wall detection is proposed. Firstly, an effective clutter mitigation method based on singular value decomposition (SVD) is used. It does not require knowledge of the background scene or rely on accurate modeling and estimation of wall parameters. Then, TWI problem is cast as a regression one and solved by means of least-squares support vector machine (LS-SVM). The complex scattering process due to the presence of the walls is automatically included in the nonlinear relationship between the feature vector extracted from the target scattered fields and the position of the target. The relationship is obtained through a training phase using LS-SVM. Simulated results show that the proposed approach is effective. We also analyze the impacts of training samples and signal-to-noise ratio (SNR) on test detection accuracy. Simulated results reveal that the proposed LS-SVM based approach can provide comparative performances in terms of accuracy, convergence, robustness, and generalization in comparison with the support vector machine (SVM) based approach. Fangfang Wang, Yerong Zhang, and Huamei Zhang Copyright © 2016 Fangfang Wang et al. All rights reserved. A Novel Dual-Band Circularly Polarized Rectangular Slot Antenna Thu, 28 Apr 2016 09:44:51 +0000 http://www.hindawi.com/journals/ijap/2016/9071610/ A coplanar waveguide fed dual-band circularly polarized rectangular slot antenna is presented. The proposed antenna consists of a rectangular metal frame acting as a ground and an S-shaped monopole as a radiator. The spatial distribution of the surface current density is employed to demonstrate that the circular polarization is generated by the S-shaped monopole which controls the path of the surface currents. An antenna prototype, having overall dimension 37 × 37 × 1 mm3, has been fabricated on FR4 substrate with dielectric constant 4.4. The proposed antenna achieves 10 dB return loss bandwidths and 3 dB axial ratio (AR) in the frequency bands 2.39–2.81 GHz and 5.42–5.92 GHz, respectively. Both these characteristics are suitable for WLAN and WiMAX applications. Biao Li, Yang Ding, and Ying-Zeng Yin Copyright © 2016 Biao Li et al. All rights reserved. Optically Controlled Reconfigurable Filtenna Tue, 19 Apr 2016 14:14:16 +0000 http://www.hindawi.com/journals/ijap/2016/7161070/ This work is regarding the development of a novel antenna called optically controlled reconfigurable filtenna, which is based on the integration of a broadband printed antenna with a bandpass reconfigurable RF filter. The filter is designed by applying defected microstrip structure (DMS) technique and positioned in printed antenna feeding line in order to keep the same size of the original antenna. The filtenna bandwidth is optically reconfigurable by using two photoconductive silicon switches excited by CW laser at 808 nm. Numerical results rely on independent and switchable operational modes through the 2.4 and 5.1 GHz ISM bands, whereas measurements demonstrate two reconfigurable modes based on single-band/dual-band operation over the same frequency bands. The proposed device is validated by theoretical, numerical, and experimental results. L. G. Silva, A. A. C. Alves, and Arismar Cerqueira Sodré Jr. Copyright © 2016 L. G. Silva et al. All rights reserved. A Moving Source Localization Method for Distributed Passive Sensor Using TDOA and FDOA Measurements Mon, 18 Apr 2016 13:56:07 +0000 http://www.hindawi.com/journals/ijap/2016/8625039/ The conventional moving source localization methods are based on centralized sensors. This paper presents a moving source localization method for distributed passive sensors using TDOA and FDOA measurements. The novel method firstly uses the steepest descent algorithm to obtain a proper initial value of source position and velocity. Then, the coarse location estimation is obtained by maximum likelihood estimation (MLE). Finally, more accurate location estimation is achieved by subtracting theoretical bias, which is approximated by the actual bias using the estimated source location and noisy data measurement. Both theoretical analysis and simulations show that the theoretical bias always meets the actual bias when the noise level is small, and the proposed method can reduce the bias effectively while keeping the same root mean square error (RMSE) with the original MLE and Taylor-series method. Meanwhile, it is less sensitive to the initial guess and attains the CRLB under Gaussian TDOA and FDOA noise at a moderate noise level before the thresholding effect occurs. Zhixin Liu, Yongjun Zhao, Dexiu Hu, and Chengcheng Liu Copyright © 2016 Zhixin Liu et al. All rights reserved. Tracking of Range and Azimuth for Continuous Imaging of Marine Target in Monopulse ISAR with Wideband Echoes Mon, 18 Apr 2016 13:38:50 +0000 http://www.hindawi.com/journals/ijap/2016/1865915/ Real-time tracking of maneuvering targets is the prerequisite for continuous imaging of moving targets in inverse synthetic aperture radar (ISAR). In this paper, the range and azimuth tracking (RAT) method with wideband radar echoes is first presented for a mechanical scanning monopulse ISAR, which is regarded as the simplest phased array unit due to the two antenna feeds. To relieve the estimation fluctuation and poor robustness of the RAT method with a single snapshot, a modified range and azimuth tracking approach based on centroid algorithm (RATCA) with forgotten factor and multiple echoes is then proposed. The performances of different forgotten factors are investigated. Both theoretical analysis and experimental results demonstrate that RATCA is superior to RAT method. Particularly, when target echo is missing occasionally, RAT method fails while RATCA still keeps good performance. The potential of continuous imaging with shipborne ISAR is verified by experimental results. With minor modification, the method proposed in this paper can be potentially applied in the phased array radar. Junhao Xie, Wei Zhou, Gongjian Zhou, Yeshu Yuan, and Shaobin Li Copyright © 2016 Junhao Xie et al. All rights reserved. Investigation on the Inversion of the Atmospheric Duct Using the Artificial Bee Colony Algorithm Based on Opposition-Based Learning Mon, 18 Apr 2016 12:09:55 +0000 http://www.hindawi.com/journals/ijap/2016/2749035/ The artificial bee colony (ABC) algorithm is a recently introduced optimization method in the research field of swarm intelligence. This paper presents an improved ABC algorithm named as OGABC based on opposition-based learning (OBL) and global best search equation to overcome the shortcomings of the slow convergence rate and sinking into local optima in the process of inversion of atmospheric duct. Taking the inversion of the surface duct using refractivity from clutter (RFC) technique as an example to validate the performance of the proposed OGABC, the inversion results are compared with those of the modified invasive weed optimization (MIWO) and ABC. The radar sea clutter power calculated by parabolic equation method using the simulated and measured refractivity profile is utilized to carry out the inversion of the surface duct, respectively. The comparative investigation results indicate that the performance of OGABC is superior to that of MIWO and ABC in terms of stability, accuracy, and convergence rate during the process of inversion. Chao Yang, Jian-Ke Zhang, and Li-Xin Guo Copyright © 2016 Chao Yang et al. All rights reserved. Optimal Pattern Synthesis of Linear Antenna Array Using Grey Wolf Optimization Algorithm Sun, 17 Apr 2016 13:20:21 +0000 http://www.hindawi.com/journals/ijap/2016/1205970/ The aim of this paper is to introduce the grey wolf optimization (GWO) algorithm to the electromagnetics and antenna community. GWO is a new nature-inspired metaheuristic algorithm inspired by the social hierarchy and hunting behavior of grey wolves. It has potential to exhibit high performance in solving not only unconstrained but also constrained optimization problems. In this work, GWO has been applied to linear antenna arrays for optimal pattern synthesis in the following ways: by optimizing the antenna positions while assuming uniform excitation and by optimizing the antenna current amplitudes while assuming spacing and phase as that of uniform array. GWO is used to achieve an array pattern with minimum side lobe level (SLL) along with null placement in the specified directions. GWO is also applied for the minimization of the first side lobe nearest to the main beam (near side lobe). Various examples are presented that illustrate the application of GWO for linear array optimization and, subsequently, the results are validated by benchmarking with results obtained using other state-of-the-art nature-inspired evolutionary algorithms. The results suggest that optimization of linear antenna arrays using GWO provides considerable enhancements compared to the uniform array and the synthesis obtained from other optimization techniques. Prerna Saxena and Ashwin Kothari Copyright © 2016 Prerna Saxena and Ashwin Kothari. All rights reserved. Design of Asymmetrical Relay Resonators for Maximum Efficiency of Wireless Power Transfer Sun, 17 Apr 2016 08:53:29 +0000 http://www.hindawi.com/journals/ijap/2016/8247476/ This paper presents a new design method of asymmetrical relay resonators for maximum wireless power transfer. A new design method for relay resonators is demanded because maximum power transfer efficiency (PTE) is not obtained at the resonant frequency of unit resonator. The maximum PTE for relay resonators is obtained at the different resonances of unit resonator. The optimum design of asymmetrical relay is conducted by both the optimum placement and the optimum capacitance of resonators. The optimum placement is found by scanning the positions of the relays and optimum capacitance can be found by using genetic algorithm (GA). The PTEs are enhanced when capacitance is optimally designed by GA according to the position of relays, respectively, and then maximum efficiency is obtained at the optimum placement of relays. The capacitance of the second resonator to th resonator and the load resistance should be determined for maximum efficiency while the capacitance of the first resonator and the source resistance are obtained for the impedance matching. The simulated and measured results are in good agreement. Bo-Hee Choi and Jeong-Hae Lee Copyright © 2016 Bo-Hee Choi and Jeong-Hae Lee. All rights reserved. Efficient Design of the Microstrip Reflectarray Antenna by Optimizing the Reflection Phase Curve Sun, 10 Apr 2016 11:25:18 +0000 http://www.hindawi.com/journals/ijap/2016/8764967/ The microstrip reflectarray antenna is an attractive directional antenna combining advantages of both the reflector and the microstrip array antenna. For the design of this kind of antenna, the conventional method, which is based on the reflection phase curve, may not be effective because of the approximations made in the design procedure. The common optimization method that employs an optimization algorithm in conjunction with the full-wave simulation to optimize the antennas’ structural parameters is able to achieve better performances in comparison with the conventional method; but it is impractical for large-scale microstrip reflectarray antennas due to too many structural parameters from variable reflection elements. To tackle the design problem of the microstrip reflectarray antenna, a new method is proposed for the first time. It optimizes the reflection phase curve rather than the structural parameters and then utilizes the optimized reflection phase curve to design the antenna. A microstrip reflectarray antenna working at 5.8 GHz and with a fixed size of 300 mm × 300 mm is designed for high gain as a sample design. The results show that the proposed method has greatly improved the antenna’s gain over 2.2 dB (from 19.7 dBi to 21.9 dBi) in comparison with the conventional design method, and it only needs to optimize 6 structural parameters, in contrast to 22 for the common optimization method. Xing Chen, Qiang Chen, Pan Feng, and Kama Huang Copyright © 2016 Xing Chen et al. All rights reserved. Investigations on Shaped Mirror Systems in Quasi-Optical Mode Converters Based on Irradiance Moments Method Thu, 07 Apr 2016 09:54:58 +0000 http://www.hindawi.com/journals/ijap/2016/8043042/ A method of transforming high-order Gaussian beams (GBs) mode into circular symmetry fundamental Gaussian beam (FGB) mode with arbitrary waist size is presented using irradiance moments method in quasi-optical (QO) mode converters. The double shaped mirrors correcting amplitude and phase simultaneously are generated by a single incidence irradiance sampling data and known ideal output FGB taking advantage of linear moment matching technique and Fresnel diffraction theory, which can be applied to a wide frequency range especially significant for terahertz band. The numerical coding procedure of creating double correcting mirrors and its fast convergence speed are discussed at 325 GHz. Numerical and experimental comparisons reveal the conclusion that enhancing surface precision and increasing moments order can improve main lobe levels. Hai Wang, Zejian Lu, Xiaoming Liu, Junsheng Yu, Yuan Yao, Xiaodong Chen, Limei Qi, and Zhijiao Chen Copyright © 2016 Hai Wang et al. All rights reserved. The RF Energy Harvesting Antennas Operating in Commercially Deployed Frequency Bands: A Comparative Study Wed, 06 Apr 2016 07:48:45 +0000 http://www.hindawi.com/journals/ijap/2016/7379624/ This paper deals with suitable antennas for energy harvesting, which is a growing research field due to the utilization of nowadays ubiquitous and abundant RF energy. Four types of basic antenna structures suitable for harvesting applications, namely, the patch antenna, slot antenna, modified inverted F antenna, and dielectric resonator antenna, are compared from the viewpoint of reflection coefficient, efficiency, radiation patterns, and dimensions. The frequencies of interest were chosen so that they cover several main wireless systems operating between 0.8 GHz and 2.6 GHz, that is, GSM, UMTS, and WiFi. M. Mrnka, P. Vasina, M. Kufa, V. Hebelka, and Z. Raida Copyright © 2016 M. Mrnka et al. All rights reserved. Retracted: A Design of Double Broadband MIMO Antenna Wed, 30 Mar 2016 12:40:18 +0000 http://www.hindawi.com/journals/ijap/2016/5975806/ International Journal of Antennas and Propagation Copyright © 2016 International Journal of Antennas and Propagation. All rights reserved. Array Pattern Synthesis Using Particle Swarm Optimization with Dynamic Inertia Weight Tue, 29 Mar 2016 09:56:18 +0000 http://www.hindawi.com/journals/ijap/2016/1829458/ A Feedback Particle Swarm Optimization (FPSO) with a family of fitness functions is proposed to minimize sidelobe level (SLL) and control null. In order to search in a large initial space and converge fast in local space to a refined solution, a FPSO with nonlinear inertia weight algorithm is developed, which is determined by a subtriplicate function with feedback taken from the fitness of the best previous position. The optimized objectives in the fitness function can obtain an accurate null level independently. The directly constrained SLL range reveals the capability to reduce SLL. Considering both element positions and complex weight coefficients, a low-level SLL, accurate null at specific directions, and constrained main beam are achieved. Numerical examples using a uniform linear array of isotropic elements are simulated, which demonstrate the effectiveness of the proposed array pattern synthesis approach. Chuang Han and Ling Wang Copyright © 2016 Chuang Han and Ling Wang. All rights reserved. A Novel Blind Source Separation Algorithm and Performance Analysis of Weak Signal against Strong Interference in Passive Radar Systems Tue, 29 Mar 2016 09:07:27 +0000 http://www.hindawi.com/journals/ijap/2016/6203972/ In Passive Radar System, obtaining the mixed weak object signal against the super power signal (jamming) is still a challenging task. In this paper, a novel framework based on Passive Radar System is designed for weak object signal separation. Firstly, we propose an Interference Cancellation algorithm (IC-algorithm) to extract the mixed weak object signals from the strong jamming. Then, an improved FastICA algorithm with -means cluster is designed to separate each weak signal from the mixed weak object signals. At last, we discuss the performance of the proposed method and verify the novel method based on several simulations. The experimental results demonstrate the effectiveness of the proposed method. Chengjie Li, Lidong Zhu, Anhong Xie, and Zhongqiang Luo Copyright © 2016 Chengjie Li et al. All rights reserved. A Wearable Wireless Energy Link for Thin-Film Batteries Charging Thu, 24 Mar 2016 08:44:43 +0000 http://www.hindawi.com/journals/ijap/2016/9365756/ A wireless charger for low capacity thin-film batteries is presented. The proposed device consists of a nonradiative wireless resonant energy link and a power management unit. Experimental data referring to a prototype operating in the ISM band centered at 434 MHz are presented and discussed. In more detail, in order to facilitate the integration into wearable accessories (such as handbags or suitcases), the prototype of the wireless energy link was implemented by exploiting a magnetic coupling between two planar resonators fabricated by using a conductive fabric on a layer of leather. From experimental data, it is demonstrated that, at 434 MHz, the RF-to-RF power transfer efficiency of the link is approximately 69.3%. As for the performance of the system as a whole, when an RF power of 7.5 dBm is provided at the input port, a total efficiency of about 29.7% is obtained. Finally, experiments performed for calculating the charging time for a low capacity thin-film battery demonstrated that, for RF input power higher than 6 dBm, the time necessary for recharging the battery is lower than 50 minutes. Giuseppina Monti, Laura Corchia, Egidio De Benedetto, and Luciano Tarricone Copyright © 2016 Giuseppina Monti et al. All rights reserved. A Hybrid Approach for Fast Computation of Multiple Incident Angles Electromagnetic Scattering Problems with Compressive Sensing and Adaptive Cross Approximation Wed, 23 Mar 2016 13:54:53 +0000 http://www.hindawi.com/journals/ijap/2016/1416094/ A hybrid compressive approach for fast computation of the electromagnetic scattering problems with multiple incident angles is proposed. The compressive sensing (CS) technique is firstly introduced to the method of moment (MoM) to reduce the number of the right-hand sides (RHS), but since the resulting excitation matrix contains linear dependency and has low-rank characteristics, the adaptive cross approximation (ACA) algorithm is used to recompress such excitation matrix, keeping only the necessary physical information. The hybrid compressive approach can reduce the number of the RHS to lower level. In fact, the ratio of the number of the RHS between the compressed excitation matrix and the original excitation matrix in the conventional MoM is close to one to fifteen. Numerical results are presented to validate the efficiency and accuracy of this method, which turns out to be highly efficient and accurate for the solution to multiple incident angles electromagnetic scattering problems. Guo-hua Wang and Yu-fa Sun Copyright © 2016 Guo-hua Wang and Yu-fa Sun. All rights reserved. Miniaturization of UWB Antennas on Organic Material Wed, 23 Mar 2016 09:57:12 +0000 http://www.hindawi.com/journals/ijap/2016/5949254/ Three planar, CPW-fed, UWB antennas with increasingly reduced size are presented and the miniaturization method is discussed. The first antenna is a CPW-fed elliptical slot with an uneven U-shaped tuning stub, the second antenna is a cactus shaped monopole, and the third one is a miniaturized version of the cactus shaped monopole antenna. All presented antennas have a simulated and measured return loss below −10 dB over the 3.1 to 10.6 GHz UWB frequency range and mostly omnidirectional radiation patterns. The proposed antennas are fabricated on liquid crystal polymer (LCP). The CPW-fed slot antenna requires an overall board dimension of 38 mm × 40 mm, and the evolved cactus monopole is confined in a 28 mm × 32 mm board, while the final miniaturized cactus monopole is printed on 28 mm × 20 mm board, resulting in a 41% and 63% size reduction, respectively. Using both simulations and measurements, the paper analyzes the response of all three antennas and discusses and demonstrates the effectiveness of the implemented miniaturization method. Symeon Nikolaou and Muhammad Ali Babar Abbasi Copyright © 2016 Symeon Nikolaou and Muhammad Ali Babar Abbasi. All rights reserved. Detection of Wideband Signal Number Based on Bootstrap Resampling Tue, 22 Mar 2016 13:48:10 +0000 http://www.hindawi.com/journals/ijap/2016/3856727/ Knowing source number correctly is the precondition for most spatial spectrum estimation methods; however, many snapshots are needed when we determine number of wideband signals. Therefore, a new method based on Bootstrap resampling is proposed in this paper. First, signals are divided into some nonoverlapping subbands; apply coherent signal methods (CSM) to focus them on the single frequency. Then, fuse the eigenvalues with the corresponding eigenvectors of the focused covariance matrix. Subsequently, use Bootstrap to construct the new resampling matrix. Finally, the number of wideband signals can be calculated with obtained vector sequences according to clustering technique. The method has a high probability of success under low signal to noise ratio (SNR) and small number of snapshots. Jiaqi Zhen Copyright © 2016 Jiaqi Zhen. All rights reserved. Designing Unimodular Waveform with Low Range Sidelobes and Stopband for Cognitive Radar via Relaxed Alternating Projection Mon, 21 Mar 2016 10:48:08 +0000 http://www.hindawi.com/journals/ijap/2016/6280508/ Cognitive radar could adapt the spectrum of waveforms in response to information regarding the changing environment, so as to avoid narrowband interference or electronic jamming. Besides stopband constraints, low range sidelobes and unimodular property are also desired. In this paper, we propose a Spectral Approximation Relaxed Alternating Projection (SARAP) method, to synthesize unimodular waveform with low range sidelobes and spectral power suppressed. This novel method, based on phase retrieval and relaxed alternating projection, could convert the correlation optimization into the spectrum approximation via the Fast Fourier Transform (FFT). Moreover, by virtue of the relaxation factor and accelerated factor, SARAP can exploit local area and more likely converge to the global solution. Numerical trials have demonstrated that SARAP could achieve excellent performance and computational efficiency which will facilitate the real-time design. Xiang Feng, Yang-chun Song, Zhi-quan Zhou, and Yi-nan Zhao Copyright © 2016 Xiang Feng et al. All rights reserved. Clutter Loss Modelling for Low Elevation Link Scenarios Mon, 21 Mar 2016 07:52:08 +0000 http://www.hindawi.com/journals/ijap/2016/1478471/ An analysis of the accuracy of several deterministic and semideterministic propagation models related to calculating clutter loss for low elevation links is presented. Predictions are compared with measurements carried out at 2 GHz over three locations. By comparing prediction and measurement techniques, improved predictive capabilities of deterministic models are demonstrated and quantified in cases where a description of the propagation environment exists and an air-to-ground scenario is considered. Pavel Valtr, Jan Zeleny, Pavel Pechac, and Martin Grabner Copyright © 2016 Pavel Valtr et al. All rights reserved. Design of Wideband Multifunction Antenna Array Based on Multiple Interleaved Subarrays Wed, 16 Mar 2016 14:07:38 +0000 http://www.hindawi.com/journals/ijap/2016/1320726/ A new Modified Iterative Fourier Technique (MIFT) is proposed for the design of interleaved linear antenna arrays which operate at different frequencies with no grating lobes, low-sidelobe levels, and wide bandwidths. In view of the Fourier transform mapping between the element excitations and array factor of uniform linear antenna array, the spectrum of the array factor is first acquired with FFT and its energy distributions are investigated thoroughly. The relationship between the carrier frequency and the element excitation is obtained by the density-weighting theory. In the following steps, the element excitations of interleaved subarrays are carefully selected in an alternate manner, which ensures that similar patterns can be achieved for interleaved subarrays. The Peak Sidelobe Levels (PSLs) of the interleaved subarrays are further reduced by the iterative Fourier transform algorithm. Numerical simulation results show that favorable design of the interleaved linear antenna arrays with different carrier frequencies can be obtained by the proposed method with favorable pattern similarity, low PSL, and wide bandwidths. Longjun Li and Buhong Wang Copyright © 2016 Longjun Li and Buhong Wang. All rights reserved. A Novel Microstrip-to-Microstrip Vertical Via Transition in X-Band Multilayer Packages Wed, 16 Mar 2016 13:28:54 +0000 http://www.hindawi.com/journals/ijap/2016/9562854/ This paper investigates a novel X-band microstrip-to-microstrip vertical via transition with matching pads loaded signal via. This design has been proposed for a multilayer substrate package. The matching pads, which are located in the center of the signal via on each ground layer, are adopted to further improve the impedance matching level and thus attain better signal transition performance. A physics-based equivalent circuit modeling approach has been employed for this research. The right angle MS-to-MS via transition was also designed using this technique. The simulated -parameters indicate that the match-pad design made a breakthrough in achieving an approximate −15 dB wide-band return loss reduction. The measured -parameter of MS-to-MS transition showed that return loss with the matching pads is better than that without the matching pads. M. X. Yu Copyright © 2016 M. X. Yu. All rights reserved. A Modeling Method for Small Packing Particles in Electromagnetic Simulation Tue, 15 Mar 2016 12:41:54 +0000 http://www.hindawi.com/journals/ijap/2016/1785751/ A modeling method for small packing particles is proposed in this paper, especially for the application of the electromagnetic simulation. This method is able to model random distributed and mutual-contacted packing particles efficiently and accurately. This modeling method is faster than a commonly used software, especially for large number of particles. The accuracy of this modeling method is validated by experiments of packing density and effective permittivity. The established model can be easily imported into commercial electromagnetic simulation software. Yi Cheng Zhong, Yu Jian Cheng, and Yong Fan Copyright © 2016 Yi Cheng Zhong et al. All rights reserved. A Compact Dielectric Resonator Antenna Excited by a Planar Monopole Patch for Wideband Applications Tue, 15 Mar 2016 12:23:24 +0000 http://www.hindawi.com/journals/ijap/2016/9734781/ A compact dielectric resonator antenna (DRA) suitable for wideband applications is presented in this paper. The proposed antenna is mainly composed by a notched cylindrical dielectric resonator (DR) coated with a metal surface on the top and a finite ground plane where the presented DR is placed. This antenna is very simple in structure and has a very low overall height of at its lowest operation frequency. A comprehensive parametric study is carried out based on Ansoft HFSS to optimize the bandwidth. The proposed antenna has been successfully simulated, optimized, fabricated, and measured. The measurement results demonstrate that the proposed design produces an impedance bandwidth of more than 75%, ranging from 2.9 GHz to 6.7 GHz for the reflection coefficient less than −10 dB. In particular, consistent broadside radiation patterns, stable gain, and high radiation efficiency are also obtained within the operation frequency band. Xuping Li, Yabing Yang, Fei Gao, Hanqing Ma, and Xiaowei Shi Copyright © 2016 Xuping Li et al. All rights reserved. Adaptive Array Beamforming Using a Chaotic Beamforming Algorithm Mon, 14 Mar 2016 12:11:31 +0000 http://www.hindawi.com/journals/ijap/2016/8354204/ The Chaotic beamforming adaptive algorithm is new adaptive method for antenna array’s radiation pattern synthesis. This adaptive method based on the optimization of the Least Mean Square algorithm using Chaos theory enables fast adaptation of antenna array radiation pattern, reduction of the noisy reference signal’s impact, and the improvement of the tracking capabilities. We performed simulations for linear and circular antenna arrays. We also compared the performances of the used and existing algorithms in terms of the radiation pattern comparison. Ana Jovanović, Luka Lazović, and Vesna Rubežić Copyright © 2016 Ana Jovanović et al. All rights reserved. A Banach Space Regularization Approach for Multifrequency Microwave Imaging Sun, 13 Mar 2016 13:45:54 +0000 http://www.hindawi.com/journals/ijap/2016/9304371/ A method for microwave imaging of dielectric targets is proposed. It is based on a tomographic approach in which the field scattered by an unknown target (and collected in a proper observation domain) is inverted by using an inexact-Newton method developed in Banach spaces. In particular, the extension of the approach to multifrequency data processing is reported. The mathematical formulation of the new method is described and the results of numerical simulations are reported and discussed, analyzing the behavior of the multifrequency processing technique combined with the Banach spaces reconstruction method. Claudio Estatico, Alessandro Fedeli, Matteo Pastorino, and Andrea Randazzo Copyright © 2016 Claudio Estatico et al. All rights reserved. A Study of Antenna System for High Order MIMO Device Thu, 10 Mar 2016 09:52:23 +0000 http://www.hindawi.com/journals/ijap/2016/1936797/ Three types of compact MIMO (Multiple-Input Multiple-Output) antenna systems with four and six elements for mobile handsets are studied in this paper. The MIMO antenna system is built on a FR4 substrate of the dimensions 136 mm × 68.8 mm × 1 mm. The antenna element is a folded planar inverted-F antenna with added resonating branches wound on a small dielectric cube of the dimensions 10 mm × 10 mm × 5 mm, which is the smallest volume so far reported covering the frequency bands 1880 MHz–1920 MHz and 2300 MHz–2620 MHz for GSM1900, LTE2300, 2.4-GHz WLAN, and LTE2500. The effects of element numbers and configurations on the system performance are investigated. More than 10 dB isolations have been achieved by properly designing the antenna elements through the use of the pattern diversity without using decoupling circuits. The envelope correlation coefficients among the elements, the mean effective gains, the efficiencies, and the multiplexing efficiencies of the elements are also discussed. Zhaoliang Chen, Wen Geyi, Ming Zhang, and Jun Wang Copyright © 2016 Zhaoliang Chen et al. All rights reserved. Substrate Integrated Slot Array Antenna with Required Radiation Pattern Envelope Thu, 10 Mar 2016 06:18:32 +0000 http://www.hindawi.com/journals/ijap/2016/4031029/ A substrate integrated slot array antenna with a prescribed radiation pattern is investigated in this paper. To meet the requirement of a certain standard radiation pattern envelope, the array configuration and the element excitation coefficient should be considered together. An efficient and systematic method is proposed to determine the element number and element weights in a planar array. After that, the geometrical dimension of the substrate integrated slot array can be synthesized. As an example, a -band 16 × 22 slot array antenna based on the substrate integrated waveguide (SIW) technology is designed, fabricated, and measured. Its radiation pattern can meet the class 3 antenna radiation pattern envelope of the European Telecommunications Standards Institute (ETSI) standard pattern. Experimental results are in good agreement with simulated ones. M. M. Zhou, Y. J. Cheng, and W. N. Huang Copyright © 2016 M. M. Zhou et al. All rights reserved. Asymmetric Shaped-Pattern Synthesis for Planar Antenna Arrays Wed, 09 Mar 2016 13:18:22 +0000 http://www.hindawi.com/journals/ijap/2016/4746381/ A procedure to synthesize asymmetrically shaped beam patterns is developed for planar antenna arrays. As it is based on the quasi-analytical method of collapsed distributions, the main advantage of this procedure is the ability to realize a shaped (null-free) region with very low ripple. Smooth and asymmetrically shaped regions can be used for Direction-of-Arrival estimation and subsequently for efficient tracking with a single output (fully analog) beamformer. T. M. Bruintjes, A. B. J. Kokkeler, and G. J. M. Smit Copyright © 2016 T. M. Bruintjes et al. All rights reserved.