International Journal of Antennas and Propagation The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Design of High-Gain and Beam Steering Antennas Using a New Planar Folded-Line Metamaterial Structure Tue, 16 Sep 2014 11:42:57 +0000 In the last few years, there has been growing interest in employing metamaterials (MTMs) to enhance antenna gain. In this paper we proposed a novel structure of planar folded-line left-handed metamaterial (FL-LHM) and applied it to improve the gain of three 5.8 GHz microstrip antenna types: a circularly polarized patch antenna, an antenna array, and a beam steering antenna. The planar FL-LHM structure was designed based on transmission line analysis. Their scattering parameters were obtained using a numerical model; the negative effective permittivity and permeability were then calculated from these parameters for the assessment of negative refraction index region. The S11 and radiation patterns of three fabricated antennas were measured; these results matched well with the simulation. We observed that the gain was increased up to 3 dBi for all the antennas. In addition, we were also able to maintain the circular polarization as well as the steering of the antenna without changing its dimensions. Minh Thuy Le, Quoc Cuong Nguyen, and Tan Phu Vuong Copyright © 2014 Minh Thuy Le et al. All rights reserved. Real-Time MIMO Channel Sounder for Emulation of Distributed Ultrawideband Systems Mon, 15 Sep 2014 08:06:50 +0000 This paper introduces an ultrawideband (UWB) channel sounding system. Its novel architecture allows real-time measurements of multiple time-variant radio propagation channels in different ultrawide frequency bands. Its architecture allows emulation of multiuser systems, sensor networks, localization systems, and distributed MIMO radar systems. The sounder uses a maximum length binary sequence (MLBS) excitation signal and correlation processing in the receiver. Its synchronous multichannel operation is supported by excellent timing stability and low power consumption of miniature size modules based upon custom integrated SiGe circuits. The paper describes the architecture, design, calibration, basic parameters, and application examples of the sounding system. Rudolf Zetik, Martin Kmec, Jürgen Sachs, and Reiner S. Thomä Copyright © 2014 Rudolf Zetik et al. All rights reserved. Interleaved-MIMO DAS for Indoor Radio Coverage: Guidelines for Planning Mon, 15 Sep 2014 00:00:00 +0000 The combination of distributed antenna systems (DAS) and multiple input multiple output (MIMO) schemes opens the way to a variety of coverage solutions for indoor environment. In this paper interleaved-MIMO (i-MIMO) DAS indoor coverage extension strategies are studied. Their performance in high-order MIMO cases is investigated in realistic conditions through LTE-A link-level simulations, based on statistical data extracted from radio channel measurements; the impact of the deployment strategy on performance is then evaluated and useful planning guidelines are derived to determine the optimum deployment for a given propagation environment. E. M. Vitucci, F. Fuschini, V. Degli-Esposti, and L. Tarlazzi Copyright © 2014 E. M. Vitucci et al. All rights reserved. A Compact Vivaldi Shaped Partially Dielectric Loaded TEM Horn Antenna for UWB Communication Wed, 10 Sep 2014 00:00:00 +0000 Ultrawideband (UWB) antennas are of huge demand and Vivaldi antennas as well as the TEM horn antennas are good candidates for UWB applications as they both have relatively simple geometry and high gain over a wide bandwidth. The aim of this study is to design a compact antenna that achieves maximum gain over a bandwidth between 1.5 and 10.6 GHz while minimizing its size. The idea is to make use of combined respective advantages of Vivaldi and TEM horn antennas to achieve the desired goals by shaping the TEM horn antenna to look like a Vivaldi antenna. The antenna structure is modified by a dielectric load in the center to increase the gain bandwidth. It is placed in a surrounding box made of PEC material to reduce the undesired side lobes and to obtain more directive radiation pattern. The simulations are performed by using the CST STUDIO SUITE electromagnetic (EM) simulation software and they are later verified by the actual measurements. The Vivaldi shaped partially dielectric loaded (VS-PDL) TEM horn antenna is proposed as a compact UWB antenna for systems using the newly established UWB band and also for the communication systems of popular bands like ISM, Wi-Fi, and GSM. Mustafa İlarslan, A. Serdar Türk, Salih Demirel, M. Emre Aydemir, and A. Kenan Keskin Copyright © 2014 Mustafa İlarslan et al. All rights reserved. Propagation of Electromagnetic Waves in Terrestrial Environment for Applications in Wireless Telecommunications Mon, 08 Sep 2014 11:50:39 +0000 Panayiotis Frangos, Dwight Jaggard, Seil Sautbekov, Georgi Georgiev, and Sava Savov Copyright © 2014 Panayiotis Frangos et al. All rights reserved. Determination of Measurement Points in Urban Environments for Assessment of Maximum Exposure to EMF Associated with a Base Station Mon, 08 Sep 2014 08:34:05 +0000 A base station (BS) antenna operates in accordance with the established exposure limits if the values of electromagnetic fields (EMF) measured in points of maximum exposure are below these limits. In the case of BS in open areas, the maximum exposure to EMF probably occurs in the antenna’s boresight direction, from a few tens to a few hundred meters away. This is not a typical scenery for urban environments. However, in the line of sight (LOS) situation, the region of maximum exposure can still be analytically estimated with good results. This paper presents a methodology for the choice of measurement points in urban areas in order to assess compliance with the limits for exposure to EMF. Agostinho Linhares, Antonio José Martins Soares, and Marco Antonio Brasil Terada Copyright © 2014 Agostinho Linhares et al. All rights reserved. Backtracking Search Optimization Algorithm for Synthesis of Concentric Circular Antenna Arrays Thu, 04 Sep 2014 00:00:00 +0000 A backtracking search optimization algorithm (BSA) is proposed for the synthesis of concentric circular antenna arrays (CCAAs) with the low sidelobe levels at a fixed beamwidth. Several numerical examples of CCAA patterns with the single, multiple, and broad nulls imposed at the directions of interference are also given to illustrate the performance and flexibility of the proposed algorithm. BSA is a relatively new population based evolutionary optimization algorithm. The numerical results show that the design of CCAA using BSA provides good sidelobe levels with a fixed beamwidth. The nulling patterns obtained by BSA are also very good. The quality of results obtained by the BSA is checked by comparing with that of several metaheuristic algorithms in the literature. BSA is also compared with differential search (DS) and bacterial foraging algorithms (BFA) in terms of iterative performances. K. Guney, A. Durmus, and S. Basbug Copyright © 2014 K. Guney et al. All rights reserved. A Novel Broadband Printed Dipole Antenna and Its Application for TD-LTE Communications Thu, 04 Sep 2014 00:00:00 +0000 Novel double-sided printed dipole antennas are proposed and investigated in this paper. Two pairs of identical T-shape metallic loadings are connected to the traditional double-sided printed dipole, enhancing the operating bandwidth. Simulations show that the proposed printed dipole without the reflecting ground plane gives a bandwidth of up to 90.7% for or 84.9% for , which is significantly greater than those of the traditional printed dipole. The proposed dipole is then applied to design a dual-polarized printed dipole antenna, mounted on a ground plane. Measurements for the prototype show a bandwidth of 68.8% for , covering the entire TD-LTE band. The gain is about 6–8 dBi and the isolation is over 24 dB over the bandwidth. Can Wang and Yuehe Ge Copyright © 2014 Can Wang and Yuehe Ge. All rights reserved. Triple Band Parasitic Array Antenna for C-X-Ku-Band Application Using Out-of-Phase Coupling Approach Wed, 03 Sep 2014 08:40:10 +0000 Triple band parasitic array antenna for C-X-Ku-band application is presented. The proposed antenna is designed using the concept of parasitic array and out-of-phase coupling approach. The objects of research are to optimize total inductance of geometry by using out-of-phase inductance approach. The out of phase inductance of geometry consists of using two U-patches novel director on the left side of geometry, appropriate dimension of ground plan, and gap coupling between parasitic and active patches. The dimension of the ground plan geometry is 0.5λ mil × 0.5154λ mil. The usable impedance bandwidth of design antenna is “5.8 GHz to 18 GHz” (102% impedance bandwidth) and gain enhancement is up to 11.8 dBi. The proposed antenna can be used for X-Ku band and C-band applications. Both simulated and measured results are presented, which are in good agreement. The proposed antenna was fabricated with a thin copper layer printed on a thin lossy FR4 substrate for low-cost production. Anubhuti Khare and Rajesh Nema Copyright © 2014 Anubhuti Khare and Rajesh Nema. All rights reserved. Triband Omnidirectional Circularly Polarized Dielectric Resonator Antenna with Top-Loaded Alford Loop Mon, 01 Sep 2014 07:54:12 +0000 A triband omnidirectional circularly polarized dielectric resonator antenna with a top-loaded modified Alford loop for GSM, WLAN, and WiMAX applications is proposed. Fed by an axial probe, the DRA (dielectric resonator antenna) radiates like a vertically polarized electric monopole. The top-loaded modified Alford loop provides an equivalent horizontally polarized magnetic dipole mode at triband. Omnidirectional CP (circular polarized) fields can be obtained when the two orthogonally polarized fields are equal in amplitude with phase quadrature. The antenna has been successfully simulated, fabricated, and measured. The experimental and numerical results exhibit that the antenna can obtain usable CP bandwidths of 1.925–1.955 GHz, 2.36–2.48 GHz, and 3.502–3.53 GHz with return loss larger than 10 dB and axial ratio less than 3 dB. In addition, over the three bands, the antenna obtains very good omnidirectional CP radiation patterns in the azimuth plane. Moreover, an average CP gain in the azimuth plane of 1.2, 1.6, and −1.5 dBic for the lower, middle, and upper bands has been obtained. Chunxia Cheng, Fushun Zhang, Yali Yao, and Fan Zhang Copyright © 2014 Chunxia Cheng et al. All rights reserved. Ultrasubwavelength Ferroelectric Leaky Wave Antenna in a Planar Substrate-Superstrate Configuration Sun, 31 Aug 2014 11:50:22 +0000 The possibility of achieving directive fan-beam radiation with planar Fabry-Pérot cavity antennas constituted by an upper ferroelectric thin film and a lower ground plane having ultrasubwavelength thickness is studied by means of a simple transverse-equivalent-network approach and a cylindrical leakywave analysis, deriving simple design formulas. The performance of the proposed antenna is investigated in terms of power density radiated at broadside and directivity in the principal planes, pointing out the main limitations and tradeoffs associated with the reduced thickness. G. Lovat, P. Burghignoli, R. Araneo, and S. Celozzi Copyright © 2014 G. Lovat et al. All rights reserved. Low-Power Optically Controlled Patch Antenna of Reconfigurable Beams Thu, 28 Aug 2014 09:45:41 +0000 A novel compact beam-reconfigurable patch antenna based on light control of no more than 30 mW optical powers is successfully demonstrated. It consists of one T-shape driven patch and one slot-etched parasitic patch. A silicon dice is employed as the photoconductive switch that is bridged across the slot center for optical control of reconfigurable beams. The antenna greatly reduces the total optical powers required for reconfigurable beams. Such design is based on the fact that the current phase change of the parasitic patch is sensitive to the conductivity of the silicon dice. A few conductivity changes of the silicon dice induced by the optical light can lead to a big phase change of the parasitic patch currents, eventually resulting in reconfigurable beams with low optical power requirement. Deshuang Zhao, Yifei Han, Feng Liang, Qiaoli Zhang, and Bing-Zhong Wang Copyright © 2014 Deshuang Zhao et al. All rights reserved. Probing Electric Field in an Enclosed Field Mapper for Characterizing Metamaterials Wed, 27 Aug 2014 11:50:56 +0000 Spatially mapping electromagnetic fields in the quasi-two-dimensional field mapper (a parallel plate waveguiding system; Justice et al. (2006)) for characterizing metamaterial devices, especially those integrating the metal boundary, may encounter troubles including electromagnetic leakage caused by the air gap and energy guiding along finitely high metal walls. To eradicate them, a moving contact approach is proposed. The physical air gap between the mobile metal walls and the stationary upper plate of the mapper is closed, while their relative movement is still allowed during the field mapping. We demonstrate the method of closing the gap by mapping the E-field distribution in a rectangular waveguide. Sucheng Li, Chendong Gu, Yadong Xu, Shahzad Anwar, Weixin Lu, Zhi Hong Hang, Bo Hou, and Huanyang Chen Copyright © 2014 Sucheng Li et al. All rights reserved. Low SAR, Simple Printed Compact Multiband Antenna for Mobile and Wireless Communication Applications Wed, 27 Aug 2014 11:26:23 +0000 Simple multiband planar antenna for wireless communication applications is presented. The proposed antenna performs four resonant modes covering multibands of wireless standards, including LTE 700, GSM, DCS, PCS, UMTS, and LTE 2300/2500. Furthermore, it covers the ISM, WiMAX, and the WLAN bands. The geometry of the proposed antenna consists of a single FR4 substrate where an open cavity fed by a coplanar U-shaped monopole is etched on one side and a short-circuited meander line in the opposite side. The cavity by its nature supports a wide range of higher frequencies, while its boundary that consists of a thin monopole resonates at 900 MHz. The meander line in the opposite side supports the LTE 700 band. The operating bands ranges are (680–748 MHz), (870–960 MHZ), (1.36–1.59 GHz), and (1.71–2.56 GHz). The antenna size is 30 × 18 × 0.8 mm3. The antenna not only has a compact size but also supports a low SAR radiation at all the operating frequencies. The proposed antenna is tested using the four recommended test positions of the CTIA association where the proposed antenna reveals good performance in all test cases in the presence of handset (keypad, battery, speaker camera, RF circuit, and LCD) in talking position, and in standby position. K. S. Sultan, H. H. Abdullah, and E. A. Abdallah Copyright © 2014 K. S. Sultan et al. All rights reserved. Dual-Feed Small-Size Penta-Band PIFA for LTE/WWAN Mobile Handset Applications Wed, 27 Aug 2014 05:43:51 +0000 A dual-feed small-size penta-band PIFA for LTE/WWAN mobile handset applications is presented. The proposed PIFA is composed of a simple U-shaped patch with dual-shorting pins connected to the ground plane. The patch, having a low profile of 5 mm, has dimensions of about 10 × 35 mm2. The antenna is excited at one arm of the U-shaped radiating patch to cover the higher band of GSM1800/1900/UMTS2100/LTE2300/2500, while it is excited at the other arm to realize the GSM900. In this way, the proposed PIFA achieves enhanced bandwidth coverage with no increased dimensions and additional active switches. In addition, the matching networks, employed on both feeds, ensure a high electrical insulation between the low and the high frequency bands, covered by the antenna. The measured antenna efficiency is 45%~50% and over 60% for the lower band and the higher band, respectively. A prototype of the proposed PIFA with dual-feed and dual-shorting pins was fabricated. The measured results including reflection coefficients and radiation characteristics are presented. Mingyang Liu and Bin Zhao Copyright © 2014 Mingyang Liu and Bin Zhao. All rights reserved. Novel Cross-Type Network for Wide-Tuning-Range Reconfigurable Multiband Antennas Tue, 26 Aug 2014 13:02:53 +0000 This paper presents a cross-type network design with a novel reconfigurable functionality to realize a tunable multiband antenna. By attaching a reconfigurable network at the feeding port of a broadband antenna, multi-input impedance adjustment enables the production of multimatching operating bands. Each band can be independently controlled by a single component with a considerably wide tuning range and high selectivity. The experiments in this study involved using an ultra-wideband (UWB) antenna connected to the proposed cross-type network. The tunable antenna operates in a dual band of (1.39 to 2.34 GHz) and (2.1 to 3.6 GHz) with tunable frequency ratios of 168% and 132%, respectively. The average bandwidths at and are approximately 50 MHz and 148 MHz, respectively, implying narrowband operation. The measured radiation pattern revealed that the tunable antenna exhibits a nearly omnidirectional radiation pattern at both 1.8 and 3.5 GHz. The network circuit architecture can be extended to the multiband function type by adopting this matching approach. The amount of shunt matches determines the number of operation bands. Chieh-Sen Lee, Chi-Lin Tsai, and Chin-Lung Yang Copyright © 2014 Chieh-Sen Lee et al. All rights reserved. Antenna Miniaturization with MEMS Tunable Capacitors: Techniques and Trade-Offs Wed, 20 Aug 2014 06:54:39 +0000 In today’s mobile device market, there is a strong need for efficient antenna miniaturization. Tunable antennas are a very promising way to reduce antenna volume while enlarging its operating bandwidth. MEMS tunable capacitors are state-of-the-art in terms of insertion loss. Their characteristics are used in this investigation. This paper uses field simulations to highlight the trade-offs between the design of the tuner and the design of the antenna, especially the impact of the location of the tuner and the degree of miniaturization. Codesigning the tuner and the antenna is essential to optimize radiated performance. Samantha Caporal Del Barrio, Art Morris, and Gert F. Pedersen Copyright © 2014 Samantha Caporal Del Barrio et al. All rights reserved. On the Bivariate Nakagami-Lognormal Distribution and Its Correlation Properties Mon, 18 Aug 2014 06:59:00 +0000 The bivariate Nakagami-lognormal distribution used to model the composite fast fading and shadowing has been examined exhaustively. In particular, we have derived the joint probability density function, the cross-moments, and the correlation coefficient in power terms. Also, two procedures to generate two correlated Nakagami-lognormal random variables are described. These procedures can be used to evaluate the robustness of the sample correlation coefficient distribution in both macro- and microdiversity scenarios. It is shown that the bias and the standard deviation of this sample correlation coefficient are substantially high for large shadowing standard deviations found in wireless communication measurements, even if the number of observations is considerable. Juan Reig, Lorenzo Rubio, and Vicent M. Rodrigo-Peñarrocha Copyright © 2014 Juan Reig et al. All rights reserved. Measurement-Based LoS/NLoS Channel Modeling for Hot-Spot Urban Scenarios in UMTS Networks Sun, 17 Aug 2014 12:21:59 +0000 A measurement campaign is introduced for modeling radio channels with either line-of-sight (LoS) or non-line-of-sight (NLoS) connection between user equipment (UE) and NodeB (NB) in an operating universal mobile telecommunications system. A space-alternating generalized expectation-maximization (SAGE) algorithm is applied to estimate the delays and the complex attenuations of multipath components from the obtained channel impulse responses. Based on a novel LoS detection method of multipath parameter estimates, channels are classified into LoS and NLoS categories. Deterministic models which are named “channel maps” and fading statistical models have been constructed for LoS and NLoS, respectively. In addition, statistics of new parameters, such as the distance between the NB and the UE in LoS/NLoS scenarios, the life-distance of LoS channel, the LoS existence probability per location and per NB, the power variation at LoS to NLoS transition and vice versa, and the transition duration, are extracted. These models are applicable for designing and performance evaluation of transmission techniques or systems used by distinguishing the LoS and NLoS channels. Jiajing Chen, Xuefeng Yin, Li Tian, Nan Zhang, Yongyu He, Xiang Cheng, Weiming Duan, and Silvia Ruiz Boqué Copyright © 2014 Jiajing Chen et al. All rights reserved. Application of Hybrid Finite Element-Boundary Integral Algorithm for Solving Electromagnetic Scattering from Multiple Objects over Rough Sea Surface Wed, 13 Aug 2014 11:39:25 +0000 A hybrid algorithm of the finite element method (FEM) is presented to solve two-dimensional (2D) scattering from multiple dielectric objects above the rough sea surface. Compared with traditional FEM based on approximate absorbing boundaries, FEM based on the boundary integral method (BIM) can reduce the calculational region and solution time of the scattering problem. In the hybrid method, the whole computational region is divided into the sea surface and multiple isolate interior regions for the dielectric objects. FEM is only used to simulate the scattering from multiple interior regions enclosing the objects, whereas the large sea is considered exactly by BIM. The coupled interaction among the isolate interior regions and the sea can be taken into account by BIM. The hybrid technique presented here is efficient and versatile for addressing scattering from multiple arbitrary targets above rough sea surfaces. Scattering properties of multiple dielectric objects above the sea surface under different conditions are discussed in detail. Run-Wen Xu and Li-Xin Guo Copyright © 2014 Run-Wen Xu and Li-Xin Guo. All rights reserved. Advanced MIMO Techniques in the Heterogeneous Networks Tue, 12 Aug 2014 13:08:35 +0000 Xiang Zhang, Lin Zhang, Guangyue Lu, Xiaoli Chu, and Yulong Zou Copyright © 2014 Xiang Zhang et al. All rights reserved. Knowledge-Aided STAP Using Low Rank and Geometry Properties Tue, 12 Aug 2014 12:40:55 +0000 This paper presents knowledge-aided space-time adaptive processing (KA-STAP) algorithms that exploit the low-rank dominant clutter and the array geometry properties (LRGP) for airborne radar applications. The core idea is to exploit the clutter subspace that is only determined by the space-time steering vectors, by employing the Gram-Schmidt orthogonalization approach to compute the clutter subspace. Simulation results illustrate the effectiveness of our proposed algorithms. Zhaocheng Yang, Rodrigo C. de Lamare, Xiang Li, and Hongqiang Wang Copyright © 2014 Zhaocheng Yang et al. All rights reserved. Graph-Based Resource Allocation for D2D Communications Underlying Cellular Networks in Multiuser Scenario Tue, 12 Aug 2014 11:41:20 +0000 With the characteristics of considerable user equipment, massive traffic and numerous local services, but limited frequency resources, the mobile communications in the future require efficient use of frequency resources. Device-to-device (D2D) communications underlying cellular networks have been considered as a promising solution to improve the resources utilization in local scenario. In this paper, we investigated the resources allocation problem in multiuser scenario and proposed a graph-based resources allocation scheme which can achieve suboptimal performance but with low computational complexity and less feedback information. Bin Guo, Shaohui Sun, and Qiubin Gao Copyright © 2014 Bin Guo et al. All rights reserved. Joint Two-Dimensional Ambiguity Resolving Based on Space-Time Filtering for MIMO-SAR Tue, 12 Aug 2014 10:54:54 +0000 In order to resolve the range and azimuth ambiguity in MIMO-SAR imaging, this paper proposed a joint two-dimensional ambiguity resolving method based on space-time filtering, which according to the ambiguity in different subscene is relative to different nearest echo range, and different azimuth time is relative to different instantaneous incidence angle, to make two-dimensional space-time steering vector for resolving ambiguity of the echo, which also can finish the imaging processing at the same time. Simulation results validate the proposed processing approach for the MIMO-SAR system. Ping-ping Huang, Hua-sheng Li, Sheng Zhang, and Guang-Cai Sun Copyright © 2014 Ping-ping Huang et al. All rights reserved. The Radiation Problem from a Vertical Hertzian Dipole Antenna above Flat and Lossy Ground: Novel Formulation in the Spectral Domain with Closed-Form Analytical Solution in the High Frequency Regime Tue, 12 Aug 2014 09:45:22 +0000 We consider the problem of radiation from a vertical short (Hertzian) dipole above flat lossy ground, which represents the well-known “Sommerfeld radiation problem” in the literature. The problem is formulated in a novel spectral domain approach, and by inverse three-dimensional Fourier transformation the expressions for the received electric and magnetic (EM) field in the physical space are derived as one-dimensional integrals over the radial component of wavevector, in cylindrical coordinates. This formulation appears to have inherent advantages over the classical formulation by Sommerfeld, performed in the spatial domain, since it avoids the use of the so-called Hertz potential and its subsequent differentiation for the calculation of the received EM field. Subsequent use of the stationary phase method in the high frequency regime yields closed-form analytical solutions for the received EM field vectors, which coincide with the corresponding reflected EM field originating from the image point. In this way, we conclude that the so-called “space wave” in the literature represents the total solution of the Sommerfeld problem in the high frequency regime, in which case the surface wave can be ignored. Finally, numerical results are presented, in comparison with corresponding numerical results based on Norton’s solution of the problem. K. Ioannidi, Ch. Christakis, S. Sautbekov, P. Frangos, and S. K. Atanov Copyright © 2014 K. Ioannidi et al. All rights reserved. Network-Coded Relaying in Multiuser Multicast D2D Network Tue, 12 Aug 2014 08:58:27 +0000 D2D communication trades short-range communication for achieving high communication rate and short communication latency. Relay aided D2D communication can further tackle the problem of intermediate obstacles blocking the communication. In this work, multidevice multicast communication via a layer of parallel relay nodes is considered. Two relaying strategies, respectively, called the conventional relaying (CR) and network-coded relaying (NCR), are proposed. The throughput of these two schemes is analytically derived and evaluated through numerical study. Theoretically, NCR shows advantage over CR in twofold: one is higher throughput and the other is requiring less relay nodes and, hence, consuming less aggregate power. Numerical studies verify the analysis and show that the throughput performance gap between the two schemes increases significantly, actually exponentially with the number of devices. Mingjun Dai, Shengli Zhang, Hui Wang, Bin Chen, Xiaohui Lin, Hongwei Liu, and Li Zhang Copyright © 2014 Mingjun Dai et al. All rights reserved. Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review Sun, 10 Aug 2014 00:00:00 +0000 An overview of the near-field-far-field (NF-FF) transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown. Renato Cicchetti, Francesco D’Agostino, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero, and Massimo Migliozzi Copyright © 2014 Renato Cicchetti et al. All rights reserved. Fading Evaluation in the 60 GHz Band in Line-of-Sight Conditions Thu, 07 Aug 2014 10:55:03 +0000 An exhaustive analysis of the small-scale fading amplitude in the 60 GHz band is addressed for line-of-sight conditions (LOS). From a measurement campaign carried out in a laboratory, we have estimated the distribution of the small-scale fading amplitude over a bandwidth of 9 GHz. From the measured data, we have estimated the parameters of the Rayleigh, Rice, Nakagami-m, Weibull, and - distributions for the small-scale amplitudes. The test of Kolmogorov-Smirnov (K-S) for each frequency bin is used to evaluate the performance of such statistical distributions. Moreover, the distributions of the main estimated parameters for such distributions are calculated and approximated for lognormal statistics in some cases. The matching of the above distributions to the experimental distribution has also been analyzed for the lower tail of the cumulative distribution function (CDF). These parameters offer information about the narrowband channel behavior that is useful for a better knowledge of the propagation characteristics at 60 GHz. J. Reig, M.-T. Martínez-Inglés, L. Rubio, V.-M. Rodrigo-Peñarrocha, and J.-M. Molina-García-Pardo Copyright © 2014 J. Reig et al. All rights reserved. Rigorous 2D Model for Study of Pulsed and Monochromatic Waves Propagation Near the Earth’s Surface Thu, 07 Aug 2014 00:00:00 +0000 A model problem considered in the paper allows solving rather complex 2D problems of the electromagnetic wave propagation with a required accuracy using conventional personal computers. The problems are of great importance for the theory and practical applications. The association of FDTD schemes with exact absorbing conditions makes up the basis for constructing models of the kind. This approach reduces the original open initial boundary value problems to the equivalent closed problems which can be solved numerically using the standard grid methods. Seil S. Sautbekov, Yuriy K. Sirenko, Nataliya P. Yashina, and Aleksey A. Vertiy Copyright © 2014 Seil S. Sautbekov et al. All rights reserved. Low-Complexity Transmit Antenna Selection and Beamforming for Large-Scale MIMO Communications Wed, 06 Aug 2014 07:45:20 +0000 Transmit antenna selection plays an important role in large-scale multiple-input multiple-output (MIMO) communications, but optimal large-scale MIMO antenna selection is a technical challenge. Exhaustive search is often employed in antenna selection, but it cannot be efficiently implemented in large-scale MIMO communication systems due to its prohibitive high computation complexity. This paper proposes a low-complexity interactive multiple-parameter optimization method for joint transmit antenna selection and beamforming in large-scale MIMO communication systems. The objective is to jointly maximize the channel outrage capacity and signal-to-noise (SNR) performance and minimize the mean square error in transmit antenna selection and minimum variance distortionless response (MVDR) beamforming without exhaustive search. The effectiveness of all the proposed methods is verified by extensive simulation results. It is shown that the required antenna selection processing time of the proposed method does not increase along with the increase of selected antennas, but the computation complexity of conventional exhaustive search method will significantly increase when large-scale antennas are employed in the system. This is particularly useful in antenna selection for large-scale MIMO communication systems. Kun Qian, Wen-Qin Wang, and Huaizong Shao Copyright © 2014 Kun Qian et al. All rights reserved.