International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. A Dual Band Patch Antenna with a Pinwheel-Shaped Slots EBG Substrate Thu, 03 Sep 2015 13:05:48 +0000 http://www.hindawi.com/journals/ijap/2015/815751/ A dual band microstrip patch antenna integrated with pinwheel-shaped electromagnetic band-gap (EBG) structures is proposed. The patch antenna consists of a pair of spiral slots on the patch and is fed by using coaxial line. Its full-wave simulation predicts dual bands from 4.43 GHz to 4.56 GHz and from 4.96 GHz to 5.1 GHz in the C-band. The designed EBG with eight pinwheel-shaped slots addresses smaller frequency drift compared with the traditional square mushroom-like EBG when applied to the patch antenna. With the help of designed EBG structure, the impedance bandwidth, radiation efficiency, and gain of the patch antenna are improved significantly. The 10 dB impedance bandwidth is extended by 3.4% and 6.5% at the low- and high-frequency bands, respectively. The radiation efficiency is increased by 5% and 17.8%, and the realized gain is enhanced by 1.87 dB and 1.56 dB at 4.57 GHz and 5.06 GHz, respectively. The designed EBG structure may have many applications in other types of planar antennas. Xiaoyan Zhang, Zhaopeng Teng, Zhiqing Liu, and Bincheng Li Copyright © 2015 Xiaoyan Zhang et al. All rights reserved. Multiple Target Localization with Bistatic Radar Using Heuristic Computational Intelligence Techniques Mon, 31 Aug 2015 05:57:06 +0000 http://www.hindawi.com/journals/ijap/2015/982967/ We assume Bistatic Phase Multiple Input Multiple Output radar having passive Centrosymmetric Cross Shape Sensor Array (CSCA) on its receiver. Let the transmitter of this Bistatic radar send coherent signals using a subarray that gives a fairly wide beam with a large solid angle so as to cover up any potential relevant target in the near field. We developed Heuristic Computational Intelligence (HCI) based techniques to jointly estimate the range, amplitude, and elevation and azimuth angles of these multiple targets impinging on the CSCA. In this connection, first the global search optimizers, that is,are developed separately Particle Swarm Optimization (PSO) and Differential Evolution (DE) are developed separately, and, to enhance the performances further, both of them are hybridized with a local search optimizer called Active Set Algorithm (ASA). Initially, the performance of PSO, DE, PSO hybridized with ASA, and DE hybridized with ASA are compared with each other and then with some traditional techniques available in literature using root mean square error (RMSE) as figure of merit. Fawad Zaman, Ijaz Mansoor Qureshi, Ata Ur Rehman, and Shujaat Ali Khan Tanoli Copyright © 2015 Fawad Zaman et al. All rights reserved. Direction of Arrival Estimation Accuracy Enhancement via Using Displacement Invariance Technique Tue, 25 Aug 2015 08:51:42 +0000 http://www.hindawi.com/journals/ijap/2015/135753/ A new algorithm for improving Direction of Arrival Estimation (DOAE) accuracy has been carried out. Two contributions are introduced. First, Doppler frequency shift that resulted from the target movement is estimated using the displacement invariance technique (DIT). Second, the effect of Doppler frequency is modeled and incorporated into ESPRIT algorithm in order to increase the estimation accuracy. It is worth mentioning that the subspace approach has been employed into ESPRIT and DIT methods to reduce the computational complexity and the model’s nonlinearity effect. The DOAE accuracy has been verified by closed-form Cramér-Rao bound (CRB). The simulation results of the proposed algorithm are better than those of the previous estimation techniques leading to the estimator performance enhancement. Youssef Fayad, Caiyun Wang, Qunsheng Cao, and Alaa El-Din Sayed Hafez Copyright © 2015 Youssef Fayad et al. All rights reserved. A Three-Component Model Based on Macropropagation Phenomena Approach for Complex Building Scattering Sun, 23 Aug 2015 12:03:06 +0000 http://www.hindawi.com/journals/ijap/2015/258060/ Multipaths represent a common predominant and uncontrolled component on channel impairments for all terrestrial and Land Mobile Satellite systems. Without restrictions w.r.t mobile terrestrial applications, the addressed multipath problematic in this paper is focused on Land Mobile Satellite applications where delayed signal replicas are highly impacting performances on communication systems while they induce strong positioning errors for navigation systems. The actual trend in propagation channel modelling is to improve the multipath characterisation and representation by using semideterministic and hybrid physical-statistical models into channel simulators instead of narrow-band empirical approaches. In this context, this paper presents a new simplified model, called 3CM (3-Component Model) to reproduce building scattering in an efficient way which strongly improves computation performances. This model is based on asymptotic methods, namely, PO (Physical Optics) which allows the 3CM to be frequency scalable, polarimetric, and dielectric materials oriented. Note that the proposed model and the retained approach can be integrated into more complex tools such as existing ray tracers. However, this issue is not discussed in this paper. Mehdi Ait-Ighil, Fernando Perez-Fontan, Joel Lemorton, Frederic Lacoste, Christophe Bourga, and Michel Bousquet Copyright © 2015 Mehdi Ait-Ighil et al. All rights reserved. Radio Capacity Estimation for Millimeter Wave 5G Cellular Networks Using Narrow Beamwidth Antennas at the Base Stations Tue, 18 Aug 2015 09:39:35 +0000 http://www.hindawi.com/journals/ijap/2015/878614/ This paper presents radio frequency (RF) capacity estimation for millimeter wave (mm-wave) based fifth-generation (5G) cellular networks using field-level simulations. It is shown that, by reducing antenna beamwidth from 65° to 30°, we can enhance the capacity of mm-wave cellular networks roughly by 3.0 times at a distance of 220 m from the base station (BS). This enhancement is far much higher than the corresponding enhancement of 1.2 times observed for 900 MHz and 2.6 GHz microwave networks at the same distance from the BS. Thus the use of narrow beamwidth transmitting antennas has more pronounced benefits in mm-wave networks. Deployment trials performed on an LTE TDD site operating on 2.6 GHz show that 6-sector site with 27° antenna beamwidth enhances the quality of service (QoS) roughly by 40% and more than doubles the overall BS throughput (while enhancing the per sector throughput 1.1 times on average) compared to a 3-sector site using 65° antenna beamwidth. This agrees well with our capacity simulations. Since mm-wave 5G networks will use arbitrary number of beams, with beamwidth much less than 30°, the capacity enhancement expected in 5G system when using narrow beamwidth antennas would be much more than three times observed in our simulations. AlMuthanna Turki Nassar, Ahmed Iyanda Sulyman, and Abdulhameed Alsanie Copyright © 2015 AlMuthanna Turki Nassar et al. All rights reserved. Full-Wave Analysis of Stable Cross Fractal Frequency Selective Surfaces Using an Iterative Procedure Based on Wave Concept Mon, 17 Aug 2015 13:46:49 +0000 http://www.hindawi.com/journals/ijap/2015/401210/ This work presents a full-wave analysis of stable frequency selective surfaces (FSSs) composed of periodic arrays of cross fractal patch elements. The shapes of these patch elements are defined conforming to a fractal concept, where the generator fractal geometry is successively subdivided into parts which are smaller copies of the previous ones (defined as fractal levels). The main objective of this work is to investigate the performance of FSSs with cross fractal patch element geometries including their frequency response and stability in relation to both the angle of incidence and polarization of the plane wave. The frequency response of FSS structures is obtained using the wave concept iterative procedure (WCIP). This method is based on a wave concept formulation and the boundary conditions for the FSS structure. Prototypes were manufactured and measured to verify the WCIP model accuracy. A good agreement between WCIP and measured results was observed for the proposed cross fractal FSSs. In addition, these FSSs exhibited good angular stability. V. P. Silva Neto, M. J. Duarte, and A. G. D’Assunção Copyright © 2015 V. P. Silva Neto et al. All rights reserved. Creeping Ray Tracing Algorithm for Arbitrary NURBS Surfaces Based on Adaptive Variable Step Euler Method Wed, 12 Aug 2015 14:23:21 +0000 http://www.hindawi.com/journals/ijap/2015/604861/ Although the uniform theory of diffraction (UTD) could be theoretically applied to arbitrarilyshaped convex objects modeled by nonuniform rational B-splines (NURBS), one of the great challenges in calculation of the UTD surface diffracted fields is the difficulty in determining the geodesic paths along which the creeping waves propagate on arbitrarilyshaped NURBS surfaces. In differential geometry, geodesic paths satisfy geodesic differential equation (GDE). Hence, in this paper, a general and efficient adaptive variable step Euler method is introduced for solving the GDE on arbitrarilyshaped NURBS surfaces. In contrast with conventional Euler method, the proposed method employs a shape factor (SF) to efficiently enhance the accuracy of tracing and extends the application of UTD for practical engineering. The validity and usefulness of the algorithm can be verified by the numerical results. Song Fu, Yun-Hua Zhang, Si-Yuan He, Xi Chen, and Guo-Qiang Zhu Copyright © 2015 Song Fu et al. All rights reserved. Ray Tracing RF Field Prediction: An Unforgiving Validation Wed, 12 Aug 2015 08:12:50 +0000 http://www.hindawi.com/journals/ijap/2015/184608/ The prediction of RF coverage in urban environments is now commonly considered a solved problem with tens of models proposed in the literature showing good performance against measurements. Among these, ray tracing is regarded as one of the most accurate ones available. In the present work, however, we show that a great deal of work is still needed to make ray tracing really unleash its potential in practical use. A very extensive validation of a state-of-the-art 3D ray tracing model is carried out through comparison with measurements in one of the most challenging environments: the city of San Francisco. Although the comparison is based on RF cellular coverage at 850 and 1900 MHz, a widely studied territory, very relevant sources of error and inaccuracy are identified in several cases along with possible solutions. E. M. Vitucci, V. Degli-Esposti, F. Fuschini, J. S. Lu, M. Barbiroli, J. N. Wu, M. Zoli, J. J. Zhu, and H. L. Bertoni Copyright © 2015 E. M. Vitucci et al. All rights reserved. A Wideband Dual-Polarized Antenna Using Planar Quasi-Open-Sleeve Dipoles for Base Station Applications Wed, 12 Aug 2015 08:01:51 +0000 http://www.hindawi.com/journals/ijap/2015/164392/ A wideband dual-polarized antenna for WLAN, WiMAX, and LTE base station applications is presented in this paper. The proposed antenna consists of two pairs of orthogonal planar quasi-open-sleeve dipoles along the centerlines, a balanced feeding structure and a square ground plane. The planar quasi-open-sleeve dipole comprises a pair of bowtie-shaped planar dipoles with two parallel curve parasitic elements. The introduced parallel curve parasitic elements change the path of the current of the original bowtie-shaped planar dipoles at high frequencies and hence wideband characteristic is achieved. Two pairs of the planar quasi-open-sleeve dipoles placed orthogonally further broaden the bandwidth of the antenna with dual-polarization characteristics. The proposed antenna achieves a 10-dB return loss bandwidth from 2.32 to 4.03 GHz (53.9% bandwidth) using the planar quasi-open-sleeve dipole structures. The isolation between the two ports remains more than 32 dB in the whole bandwidth. Measured results show that the proposed antenna keeps the cross-polarization under −33 dB and the front-to-back ratio better than 15 dB in the operating band. The antenna has an area of 0.3λ  × 0.3λ at 2.32 GHz making it easy to be extended to an array element. Guan-xi Zhang, Li Sun, and Bao-hua Sun Copyright © 2015 Guan-xi Zhang et al. All rights reserved. Conformal Array Pattern Synthesis and Activated Elements Selection Strategy Based on PSOGSA Algorithm Tue, 11 Aug 2015 06:41:32 +0000 http://www.hindawi.com/journals/ijap/2015/858357/ The pattern synthesis and activated element selection for conformal array is investigated based on hybrid particle swarm optimization-gravitational search algorithm (PSOGSA) in this paper. With the introduction of PSOGSA algorithm which is a novel hybrid optimization technique, the element excitations are optimized to obtain the desired pattern for conformal array in the case of considering uncoupled and coupled element pattern. Numerical simulation and full-wave electromagnetic calculation verify the advantage and efficiency of our method. Then, a novel strategy of activated element selection based on PSOGSA algorithm is proposed for saving the energy consumption in conformal array. Bin Sun, Chunheng Liu, Yang Liu, Xiaofang Wu, Yongzhen Li, and Xuesong Wang Copyright © 2015 Bin Sun et al. All rights reserved. Dual-Polarized Planar Phased Array Analysis for Meteorological Applications Thu, 06 Aug 2015 11:13:56 +0000 http://www.hindawi.com/journals/ijap/2015/340704/ This paper presents a theoretical analysis for the accuracy requirements of the planar polarimetric phased array radar (PPPAR) in meteorological applications. Among many factors that contribute to the polarimetric biases, four factors are considered and analyzed in this study, namely, the polarization distortion due to the intrinsic limitation of a dual-polarized antenna element, the antenna pattern measurement error, the entire array patterns, and the imperfect horizontal and vertical channels. Two operation modes, the alternately transmitting and simultaneously receiving (ATSR) mode and the simultaneously transmitting and simultaneously receiving (STSR) mode, are discussed. For each mode, the polarimetric biases are formulated. As the STSR mode with orthogonal waveforms is similar to the ATSR mode, the analysis is mainly focused on the ATSR mode and the impacts of the bias sources on the measurement of polarimetric variables are investigated through Monte Carlo simulations. Some insights of the accuracy requirements are obtained and summarized. Chen Pang, Peter Hoogeboom, François Le Chevalier, Herman W. J. Russchenberg, Jian Dong, Tao Wang, and Xuesong Wang Copyright © 2015 Chen Pang et al. All rights reserved. Dual Circularly Polarized Omnidirectional Antenna with Slot Array on Coaxial Cylinder Thu, 06 Aug 2015 11:10:23 +0000 http://www.hindawi.com/journals/ijap/2015/127820/ A dual circularly polarized (CP) omnidirectional antenna based on slot array in coaxial cylinder structure is presented in this paper. It is constructed by perpendicular slot pairs around and along the axis of the coaxial cylinder to realize the omnidirectional CP property, and two ports are assigned in its two sides as left hand circularly polarized (LHCP) port and right hand circularly polarized (RHCP) port, respectively. The proposed antenna achieves a bandwidth of 16.4% ranging from 5.05 to 5.95 GHz with an isolation higher than 15 dB between the two CP ports, and the return loss (RL) is higher than 10 dB within the bandwidth in both of the two ports. From the measured results, the average axial ratio (AR) of the proposed antenna in omnidirectional plane is lower than 1.5 dB. Bin Zhou, Junping Geng, Zhe Li, Wenzhi Wang, Xianling Liang, and Ronghong Jin Copyright © 2015 Bin Zhou et al. All rights reserved. Robust Spectrum Sensing Demonstration Using a Low-Cost Front-End Receiver Wed, 05 Aug 2015 13:58:44 +0000 http://www.hindawi.com/journals/ijap/2015/464982/ Spectrum Sensing (SS) is an important function in Cognitive Radio (CR) to detect primary users. The design of SS algorithms is one of the most challenging tasks in CR and requires innovative hardware and software solutions to enhance detection probability and minimize low false alarm probability. Although several SS algorithms have been developed in the specialized literature, limited work has been done to practically demonstrate the feasibility of this function on platforms with significant computational and hardware constraints. In this paper, SS is demonstrated using a low cost TV tuner as agile front-end for sensing a large portion of the Ultra-High Frequency (UHF) spectrum. The problems encountered and the limitations imposed by the front-end are analysed along with the solutions adopted. Finally, the spectrum sensor developed is implemented on an Android device and SS implementation is demonstrated using a smartphone. Daniele Borio, Emanuele Angiuli, Raimondo Giuliani, and Gianmarco Baldini Copyright © 2015 Daniele Borio et al. All rights reserved. Smart Wireless Power Transfer Operated by Time-Modulated Arrays via a Two-Step Procedure Tue, 04 Aug 2015 13:52:36 +0000 http://www.hindawi.com/journals/ijap/2015/673536/ The paper introduces a novel method for agile and precise wireless power transmission operated by a time-modulated array. The unique, almost real-time reconfiguration capability of these arrays is fully exploited by a two-step procedure: first, a two-element time-modulated subarray is used for localization of tagged sensors to be energized; the entire 16-element TMA then provides the power to the detected tags, by exploiting the fundamental and first-sideband harmonic radiation. An investigation on the best array architecture is carried out, showing the importance of the adopted nonlinear/full-wave computer-aided-design platform. Very promising simulated energy transfer performance of the entire nonlinear radiating system is demonstrated. Diego Masotti, Alessandra Costanzo, and Vittorio Rizzoli Copyright © 2015 Diego Masotti et al. All rights reserved. Integral Equation Analysis of EM Scattering from Multilayered Metallic Photonic Crystal Accelerated with Adaptive Cross Approximation Tue, 04 Aug 2015 11:21:17 +0000 http://www.hindawi.com/journals/ijap/2015/274307/ A space-domain integral equation method accelerated with adaptive cross approximation (ACA) is presented for the fast and accurate analysis of electromagnetic (EM) scattering from multilayered metallic photonic crystal (MPC). The method directly solves for the electric field in order to easily enable the periodic boundary condition (PBC) in the spatial domain. The ACA is a purely algebraic method allowing the compression of fully populated matrices; hence, its formulation and implementation are independent of integral equation kernel (Green’s function). Therefore, the ACA is very well suited for accelerating integral equation analysis of periodic structure with the integral kernel of the periodic Green’s function (PGF). The computation of the spatial-domain periodic Green’s function (PGF) is accelerated by the modified Ewald transformation, such that the multilayered periodic structure can be analyzed efficiently and accurately. An effective interpolation method is also proposed to fast compute the periodic Green’s function, which can greatly reduce the time of matrix filling. Numerical examples show that the proposed method can greatly save the frequency sweep time for multilayered periodic structure. Jianxun Su, Zengrui Li, Xujin Yuan, Yaoqing (Lamar) Yang, and Junhong Wang Copyright © 2015 Jianxun Su et al. All rights reserved. A Compact Experimental Planar Antenna with a USB Connector for Mobile Phone Application Mon, 03 Aug 2015 14:22:09 +0000 http://www.hindawi.com/journals/ijap/2015/217241/ A practical antenna design combined with a universal serial bus (USB) connector in close vicinity is proposed. In the proposed arrangement, the antenna unit consisted of two planar inverted F antennas (PIFAs) placed on the two sides of the USB connector. The antenna is located at the bottom of the mobile phone to avoid the crowded space on the top side of the phone where various mobile phone accessories are usually assigned. A diplexer is incorporated in the unit to alleviate the adverse effect of the metal USB connector on the radiating efficiency of the antenna. A prototype antenna was fabricated and tested and showed good coverage for GSM850/900/1800/1900, UMTS2100, and LTE700/2500 multibands operation. The overall performances demonstrated the good design of the proposed unit for mobile phone application. Cheng-Hung Lin and Kwong-Kau Tiong Copyright © 2015 Cheng-Hung Lin and Kwong-Kau Tiong. All rights reserved. A Building-Block Favoring Method for the Topology Optimization of Internal Antenna Design Sun, 02 Aug 2015 11:32:12 +0000 http://www.hindawi.com/journals/ijap/2015/206243/ This paper proposes a new design technique for internal antenna development. The proposed method is based on the framework of topology optimization incorporated with three effective mechanisms favoring the building blocks of associated optimization problems. Conventionally, the topology optimization of antenna structures discretizes a design space into uniform and rectangular pixels. However, the defining length of the resultant building blocks is so large that the problem difficulty arises; furthermore, the order of the building blocks becomes extremely high, so genetic algorithms (GAs) and binary particle swarm optimization (BPSO) are not more efficient than the random search algorithm. In order to form tight linkage groups of building blocks, this paper proposes a novel approach to handle the design details. In particular, a nonuniform discretization is adopted to discretize the design space, and the initialization of GAs is assigned as orthogonal arrays (OAs) instead of a randomized population; moreover, the control map of GAs is constructed by ensuring the schema growth based on the generalized schema theorem. By using the proposed method, two internal antennas are thus successfully developed. The simulated and measured results show that the proposed technique significantly outperforms the conventional topology optimization. Yen-Sheng Chen Copyright © 2015 Yen-Sheng Chen. All rights reserved. MIMO Antenna Design and Channel Modeling 2014 Thu, 30 Jul 2015 07:52:27 +0000 http://www.hindawi.com/journals/ijap/2015/675650/ Wenhua Chen, Manos M. Tentzeris, Neil Trappe, Yuan Yao, Yan Zhang, and Xinyi Tang Copyright © 2015 Wenhua Chen et al. All rights reserved. Compressive Sensing for High-Resolution Direction-of-Arrival Estimation via Iterative Optimization on Sensing Matrix Wed, 29 Jul 2015 13:31:09 +0000 http://www.hindawi.com/journals/ijap/2015/713930/ A novel compressive sensing- (CS-) based direction-of-arrival (DOA) estimation algorithm is proposed to solve the performance degradation of the CS-based DOA estimation in the presence of sensing matrix mismatching. Firstly, a DOA sparse sensing model is set up in the presence of sensing matrix mismatching. Secondly, combining the Dantzig selector (DS) algorithm and least-absolute shrinkage and selection operator (LASSO) algorithm, a CS-based DOA estimation algorithm which performs iterative optimization alternatively on target angle information vector and sensing matrix mismatching error vector is proposed. The simulation result indicates that the proposed algorithm possesses higher angle resolution and estimation accuracy compared with conventional CS-based DOA estimation algorithms. Hongtao Li, Chaoyu Wang, and Xiaohua Zhu Copyright © 2015 Hongtao Li et al. All rights reserved. A Novel Miniaturized Dual Slant-Polarized UWB Antenna Array with Excellent Pattern Symmetry Property for MIMO Applications Wed, 29 Jul 2015 07:54:07 +0000 http://www.hindawi.com/journals/ijap/2015/801638/ A novel miniaturized 1 × 10 uniform linear dual slant-polarized UWB antenna array for MIMO base station is presented. The antenna array operates in the frequency band from 1710 to 2690 MHz with a 17.3–18.7 dBi gain in a size of 105 × 1100 × 37 mm. The array element is composed of two single-polarized dipoles evolved from bow-tie antenna with slots on them, which miniaturize the size of the antenna. The 10 array elements are fed through an air dielectric strip-line power splitter. Two parameters, the beam tracking and the beam squint, are presented to quantitatively describe the pattern symmetry property of the antenna. The simulated and measured radiation performances are studied and compared. The results show that the pattern symmetry property of the single antenna element has been improved about 24% compared with the former study, and the antenna array also provides excellent pattern symmetry property. Zhi Zeng, Jianjun Huang, Zhaohui Song, and Qinyu Zhang Copyright © 2015 Zhi Zeng et al. All rights reserved. Design of a Minimized Complementary Illusion Cloak with Arbitrary Position Tue, 28 Jul 2015 11:24:53 +0000 http://www.hindawi.com/journals/ijap/2015/932495/ This paper has developed a complementary illusion cloak to hide the objects with arbitrary shapes and sizes. In the proposed cloak, a complementary cloak is first introduced by using the trapezoid coordinate transformation. Then an illusion device in terms of another trapezoid coordinate transformation is designed to cloak the object. With two coordinate transformations, the complementary illusion cloak device can be arbitrarily placed to hide the target object, and the sizes of the antiobject used to cloak the object are obviously compressed. Numerical results including target objects with different shapes are given to verify correctness and effectiveness of the proposed cloak. Yan Shi, Lin Zhang, Wei Tang, Long Li, and Chang-Hong Liang Copyright © 2015 Yan Shi et al. All rights reserved. LTE Technology: Antenna, RF Front-Ends, and Channel Modeling Tue, 28 Jul 2015 07:57:25 +0000 http://www.hindawi.com/journals/ijap/2015/764178/ Qingfeng Zhang, Sai Wai Wong, Cheng Jin, Xiu Yin Zhang, Yifan Chen, Dimitrios Sounas, and Nima Chamanara Copyright © 2015 Qingfeng Zhang et al. All rights reserved. DOA Estimation for Mixed Uncorrelated and Coherent Sources in Multipath Environment Mon, 27 Jul 2015 13:20:14 +0000 http://www.hindawi.com/journals/ijap/2015/636545/ A novel direction-of-arrival (DOA) estimation method is proposed to cope with the scenario where a number of uncorrelated and coherent narrowband sources simultaneously impinge on the far-field of a uniform linear array (ULA). In the proposed method, the DOAs of uncorrelated sources are firstly estimated by utilizing the property of the moduli of eigenvalues of the DOA matrix. Afterwards, the contributions of uncorrelated sources and the interference of noise are eliminated completely by exploiting the improved spatial differencing technique and only the coherent components remain in the spatial differencing matrix. Finally, the remaining coherent sources can be resolved by performing the improved spatial smoothing scheme on the spatial differencing matrix. The presented method can resolve more number of sources than that of the array elements and distinguish the uncorrelated and coherent sources that come from the same direction as well as improving the estimation performance. Simulation results demonstrate the effectiveness and efficiency of the proposed method. Heping Shi, Wen Leng, Anguo Wang, and Tongfeng Guo Copyright © 2015 Heping Shi et al. All rights reserved. Compact Unequal Power Divider with Filtering Response Mon, 27 Jul 2015 13:14:33 +0000 http://www.hindawi.com/journals/ijap/2015/658102/ We present a novel unequal power divider with bandpass responses. The proposed power divider consists of five resonators and a resistor. The power division ratio is controlled by altering the coupling strength among the resonators. The output ports have the characteristic impedance of 50 Ω and impedance transformers in classical Wilkinson power dividers are not required in this design. Use of resonators enables the filtering function of the power divider. Two transmission zeros are generated near the passband edges, resulting in quasielliptic bandpass responses. For validation, a 2 : 1 filtering power divider is implemented. The fabricated circuit size is 0.22 λg  0.08 λg, featuring compact size for unequal filtering power dividers, which is suitable for the feeding networks of antenna arrays. Wei-Qiang Pan, Jin-Xu Xu, Kai Xu Wang, and Xiao Lan Zhao Copyright © 2015 Wei-Qiang Pan et al. All rights reserved. Dual-Frequency Two-Element Antenna Array with Suppressed Mutual Coupling Mon, 27 Jul 2015 12:50:05 +0000 http://www.hindawi.com/journals/ijap/2015/912934/ An efficient technique utilizing the defected ground structure (DGS) to suppress the mutual coupling effect of a dual-frequency microstrip antenna array is studied. The proposed dual-frequency DGS beneath two patches includes two circular split ring slots, each of which corresponds to one resonant frequency of the patches. The characteristic of the compact DGS is theoretically and experimentally investigated. The prototypes of the patches arrays with and without the proposed DGS are fabricated. Both the simulated and measured results show that the mutual coupling between array elements has been obviously reduced at the two operating frequency bands with the implementation of the proposed DGS structure. Yantao Yu, Lijun Yi, Xiaoya Liu, Zhaokai Gu, and Nadia Media Rizka Copyright © 2015 Yantao Yu et al. All rights reserved. MIMO Antenna with High Isolation for WBAN Applications Mon, 27 Jul 2015 12:49:40 +0000 http://www.hindawi.com/journals/ijap/2015/370763/ A multi-input multi-output (MIMO) antenna with high isolation is proposed for 2.4 GHz ISM band (2.4–2.485 GHz) WBAN applications. The proposed MIMO antenna consists of two PIFA elements and utilizes an isolator composed of a shorted strip and two slits in the ground plane. Although the separation between the two PIFAs is minimized to 8 mm (0.06 ), isolation performance is improved by virtue of an isolator. To analyze the antenna’s performance on a human body, the proposed antenna is placed on a human muscle-equivalent flat phantom and is investigated through simulations. The measured −10 dB reflection coefficient bandwidth of the antenna ranges from 2.11 GHz to 2.6 GHz, and the isolation is lower than −38 dB over the 2.4 GHz ISM band. Do-Gu Kang, Jinpil Tak, and Jaehoon Choi Copyright © 2015 Do-Gu Kang et al. All rights reserved. A Novel Metamaterial MIMO Antenna with High Isolation for WLAN Applications Mon, 27 Jul 2015 12:24:56 +0000 http://www.hindawi.com/journals/ijap/2015/851904/ A compact metamaterial-MIMO antenna for WLAN applications is presented in this paper. The MIMO antenna is designed by placing side by side two single metamaterial antennas which are constructed based on the modified composite right/left-handed (CRLH) model. By adding another left-handed inductor, the total left-handed inductor of the modified CRLH model is increased remarkably in comparison with that of conventional CRLH model. As a result, the proposed metamaterial antenna achieves 60% size reduction in comparison with the unloaded antenna. The MIMO antenna is electrically small (30 mm × 44 mm) with an edge-to-edge separation between two antennas of at 2.4 GHz. In order to reduce the mutual coupling of the antenna, a defected ground structure (DGS) is inserted to suppress the effect of surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.38 GHz to 2.5 GHz, which entirely covers WLAN frequency band allocated from 2.4 GHz to 2.48 GHz. The antenna also shows a high isolation coefficient which is less than −35 dB over the operating frequency band. A good agreement between simulation and measurement is shown in this context. Nguyen Khac Kiem, Huynh Nguyen Bao Phuong, Quang Ngoc Hieu, and Dao Ngoc Chien Copyright © 2015 Nguyen Khac Kiem et al. All rights reserved. Linear Array Design with Switched Beams for Wireless Communications Systems Mon, 27 Jul 2015 12:08:11 +0000 http://www.hindawi.com/journals/ijap/2015/278160/ This paper presents an analysis for optimal design of switched beamforming applied to a linear array for wireless communication systems. The beam switching scheme provides coverage of a given sector in azimuth and controls the sidelobe level simultaneously. The analysis was developed considering arrays composed of Quasi-Yagi elements. The model assumes a user moving in the azimuthal direction under a constant velocity and with an estimation of the signal-to-noise ratio (SNR) at the mobile user (MU). The radio base station applies the beam that yields the best performance during transmission. The decision is based on the feedback information received from the MU. The goal of the analysis is to determine the best trade-off between the array size and number of feedback bits necessary to maximize the SNR at the receiver. The results show that a compromise between the number of beam-pointing directions and the array size should be taken into consideration for a wireless communication system design. Vinícius Ludwig-Barbosa, Edson Schlosser, Renato Machado, Filipe Guterres Ferreira, Sabrina Müller Tolfo, and Marcos Vinício Thomas Heckler Copyright © 2015 Vinícius Ludwig-Barbosa et al. All rights reserved. 2D Active Antenna Array Design for FD-MIMO System and Antenna Virtualization Techniques Mon, 27 Jul 2015 12:05:49 +0000 http://www.hindawi.com/journals/ijap/2015/873530/ Full dimension MIMO (FD-MIMO) is one of the key technologies presently studied in the 3GPP for the next generation long-term evolution advanced (LTE-A) systems. By incorporating FD-MIMO into LTE/LTE-A systems, it is expected that system throughput will be drastically improved beyond what is possible in conventional LTE systems. This paper presets details on the 2D active antenna array design for FD-MIMO systems supporting 32 antenna elements. The FD-MIMO system allows for dynamic and adaptive precoding to be performed jointly across all antennas thus achieving more directional transmissions in the azimuth and elevation domains simultaneously, to a larger number of users. Finally, we discuss 2D antenna array port virtualization techniques for creating beams with wide coverage, necessary for broadcasting signals to all users within a sector, such as the CRS (Common Reference Signal). Ioannis Tzanidis, Yang Li, Gary Xu, Ji-Yun Seol, and JianZhong (Charlie) Zhang Copyright © 2015 Ioannis Tzanidis et al. All rights reserved. A CPW-Fed Quasi-PIFA Antenna Using Quasi-Lumped Resonators for Mobile Phones Mon, 27 Jul 2015 11:58:33 +0000 http://www.hindawi.com/journals/ijap/2015/715958/ A novel single CPW-fed Quasi-Planar Inverted-F Antenna (PIFA) using quasi-lumped elements is developed for mobile communication handheld terminals operating at 2.6 GHz. The antenna is composed of an inductor covered by a set of interdigital and parasitic capacitors. The proposed antenna achieves a measured bandwidth of 11% for return loss with the antenna gain of about 4 dBi. The antenna is designed in single layer (zero height) which is appropriate to be used in thin devices where a small room is considered for the antenna. The proposed antenna is suitable for use in Long Term Evolution band 7. The operating frequency of introduced antenna depends on the number of interdigital fingers and inductor length rather than the total resonator patch only, so that the operating frequency can be altered while the total patch size remains unchanged. The calculated operating frequency is confirmed by simulation and measurement. Also the dipole-like simulated radiation pattern is confirmed by measurement. Majid Rafiee, Mohd Fadzil bin Ain, and Aftanasar Md. Shahar Copyright © 2015 Majid Rafiee et al. All rights reserved.