International Journal of Antennas and Propagation The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. A Broadband and High Gain Tapered Slot Antenna for W-Band Imaging Array Applications Sun, 23 Nov 2014 09:25:42 +0000 A broadband and high gain tapered slot antenna (TSA) by utilizing a broadband microstrip- (MS-) to-coplanar stripline (CPS) balun has been developed for millimeter-wave imaging systems and sensors. This antenna exhibits ultrawideband performance for frequency ranges from 70 to over 110 GHz with the high antenna gain, low sidelobe levels, and narrow beamwidth. The validity of this antenna as imaging arrays is also demonstrated by analyzing mutual couplings and 4-element linear array. This antenna can be applied to mm-wave phased array, imaging array for plasma diagnostics applications. Dong Sik Woo, Kang Wook Kim, and Hyun-Chul Choi Copyright © 2014 Dong Sik Woo et al. All rights reserved. A Flexible Monopole Antenna with Dual-Notched Band Function for Ultrawideband Applications Thu, 20 Nov 2014 11:45:42 +0000 We present a flexible ultrawideband (UWB) planar monopole antenna with dual-notched band characteristic printed on a polyimide substrate. The antenna is fed by a step coplanar waveguide (CPW) that provides smooth transitional impedance for improved matching. It operates from 2.76 to 10.6 GHz with return loss greater than 10 dB except for the notch band to reduce the interference with existing 3.5 GHz WiMAX band and 5.5 GHz WLAN band. With a combination of rectangular and circle patches in which the U-shaped slot is carved, the overall size of antenna is 30 mm × 20 mm. Moreover, a pair of arc-shaped stubs located at both sides of the feed line is utilized to create the notch band for WiMAX band. The results also show that the antenna has omnidirectional radiation pattern and smooth gain over the entire operational band. Xiaoyan Zhang and Guohao Wang Copyright © 2014 Xiaoyan Zhang and Guohao Wang. All rights reserved. Design of Highly Isolated Compact Antenna Array for MIMO Applications Thu, 20 Nov 2014 06:00:26 +0000 In order to achieve very high data rates in both the uplink and downlink channels, the multiple antenna systems are used within the mobile terminal as well as the base station of the future generation of mobile networks. When implemented in a size limited platform, the multiple antenna arrays suffer from strong mutual coupling between closely spaced array elements. In this paper, a rigorous procedure for the design of a 4-port compact planar antenna array with high port isolation is presented. The proposed design involves a decoupling network consisting of reactive elements, whose values can be obtained by the method of eigenmode analysis. Numerical results show the effectiveness of the proposed design approach in improving the port isolation of a compact four-element planar array. Tiancong Huang, Yantao Yu, and Lijun Yi Copyright © 2014 Tiancong Huang et al. All rights reserved. Development of Ultra-Broadband Base Station Antenna for All Mainstream LTE 700/800/900 MHz Frequency Bands Thu, 20 Nov 2014 00:00:00 +0000 LTE deployment is being accelerated due to its improved radio access structure meeting the requirements of current and next generation of wireless networks. Its low band application presents useful aspects such as low density of base station while providing good in-building penetration. In this work, we design and develop a dual-polarized base station antenna supporting 698 MHz to 960 MHz with an azimuth-plan half-power beam width of 90° covering all mainstream LTE 700/800/900 MHz frequency bands representing the widest low frequency range being actively used in the current mobile communication industry. In the design process, rigorous algorithm based on swarm method is developed to tune the electrical performances under strict base station antenna requirements. Experimental results from pattern tests demonstrate the design analysis and the significant advantages of using swarm method in the antenna development process. Doudou Samb, Zhonglin Wu, Mulin Liu, and Hu Bin Jie Copyright © 2014 Doudou Samb et al. All rights reserved. Monte Carlo Simulation of the Echo Signals from Low-Flying Targets for Airborne Radar Mon, 17 Nov 2014 11:38:19 +0000 A demonstrated hybrid method based on the combination of half-space physical optics method (PO), graphical-electromagnetic computing (GRECO), and Monte Carlo method on echo signals from low-flying targets based on actual environment for airborne radar is presented in this paper. The half-space physical optics method , combined with the graphical-electromagnetic computing (GRECO) method to eliminate the shadow regions quickly and rebuild the target automatically, is employed to calculate the radar cross section (RCS) of the conductive targets in half space fast and accurately. The direct echo is computed based on the radar equation. The reflected paths from sea or ground surface cause multipath effects. In order to accurately obtain the echo signals, the phase factors are modified for fluctuations in multipath, and the statistical average value of the echo signals is obtained using the Monte Carlo method. A typical simulation is performed, and the numerical results show the accuracy of the proposed method. Mingyuan Man, Zhenya Lei, Yongjun Xie, Botao Chen, and Qing Wang Copyright © 2014 Mingyuan Man et al. All rights reserved. Compact Shorted Stacked-Patch Antenna Integrated with Chip-Package Based on LTCC Technology Sun, 16 Nov 2014 00:00:00 +0000 A low profile chip-package stacked-patch antenna is proposed by using low temperature cofired ceramic (LTCC) technology. The proposed antenna employs a stacked-patch to achieve two operating frequency bands and enhance the bandwidth. The height of the antenna is decreased to 4.09 mm (about /25 at 2.45 GHz) due to the shorted pin. The package is mounted on a 44 × 44 mm2 ground plane to miniaturize the volume of the system. The design parameters of the antenna and the effect of the antenna on chip-package cavity are carefully analyzed. The designed antenna operates at a center frequency of 2.45 GHz and its impedance bandwidth is 200 MHz, resulting from two neighboring resonant frequencies at 2.41 and 2.51 GHz, respectively. The average gain across the frequency band is about 5.28 dBi. Yongjiu Li, Long Li, Xiwang Dai, Cheng Zhu, Feifei Huo, and Gang Dong Copyright © 2014 Yongjiu Li et al. All rights reserved. Rectangular Ring Antenna Excited by Circular Disc Monopole for WiMAX System Thu, 13 Nov 2014 11:35:39 +0000 This research presents a rectangular ring antenna excited by a circular disc monopole (CDM) mounted in front of a square reflector. The proposed antenna is designed to cover a frequency range of 2.300–5.825 GHz and thereby is suitable for WiMAX applications. Multiple parametric studies were carried out using the CST Microwave Studio simulation program. A prototype antenna was fabricated and experimented. The measurements were taken and compared with the simulation results, which indicates good agreement between both results. The prototype antenna produces an impedance bandwidth ( < −10 dB) that covers the WiMAX frequency range and a constant unidirectional radiation pattern ( and ). The minimum and maximum gains are 3.7 and 8.7 dBi, respectively. The proposed antenna is of compact size and has good unidirectional radiation performance. Thus, it is very suitable for a multitude of WiMAX applications. Souphanna Vongsack, Chuwong Phongcharoenpanich, Sompol Kosulvit, Kazuhiko Hamamoto, and Toshio Wakabayashi Copyright © 2014 Souphanna Vongsack et al. All rights reserved. Deployment Challenges for Large-Scale MIMO Communications Sun, 09 Nov 2014 12:42:49 +0000 Ahmed Iyanda Sulyman, Joonhyuk Kang, and Shahram Yousefi Copyright © 2014 Ahmed Iyanda Sulyman et al. All rights reserved. On the Accuracy of Asymptotic Solutions for TM Waves Diffracting on an Impedance Wedge Sun, 09 Nov 2014 12:29:08 +0000 The contribution focuses on the accuracy of two asymptotic solutions aimed at representing the electromagnetic field scattered by penetrable wedges. One is a heuristic manipulation of the solution for the perfect electrical conductor, and the other one is a more rigorous coefficient based on approximate boundary conditions. The results presented here extend those proposed by other authors by illustrating the accuracy of such solutions at the edge of validity of the uniform theory of diffraction. In particular, they show that the heuristic formulation can be freely applied in similar conditions, while the other might not always lead to accurate predictions. Sonia Fu, Pierre Jacolot, Tommaso Balercia, Christian Rom, Jørgen B. Andersen, and Gert F. Pedersen Copyright © 2014 Sonia Fu et al. All rights reserved. A Novel CPW-Fed UWB Antenna with Band-Stop Function Sun, 09 Nov 2014 09:55:47 +0000 A novel coplanar waveguide-fed (CPW) ultrawideband (UWB) antenna with band-stop function is presented in this paper. The proposed antenna comprises a CPW-fed slot rectangular patch with an open stub ground plane, and two inverted L-shaped strip conductors are fabricated on the back plane. The overall size of the antenna is 25 × 25 × 1.6 mm2, and it achieves good impedance matching and radiation gain. Simulated and measured results show that the designed antenna operates at 2.9 GHz–13.08 GHz with band rejection in the frequency band of 7.7 GHz–9.05 GHz for satellite applications, and the proposed antenna is suitable for UWB wireless communication applications. Huaming Chen, Zhengrong Li, Baiyu Li, and Guangfu Sun Copyright © 2014 Huaming Chen et al. All rights reserved. Design of a Small Modified Minkowski Fractal Antenna for Passive Deep Brain Stimulation Implants Tue, 04 Nov 2014 00:00:00 +0000 A small planar modified Minkowski fractal antenna is designed and simulated in dual frequency bands (2.4 and 5.8 GHz) for wireless energy harvesting by deep brain stimulation (DBS) devices. The designed antenna, physically being confined inside a miniaturized structure, can efficiently convert the wireless signals in dual ISM frequency bands to the energy source to recharge the DBS battery or power the pulse generator directly. The performance metrics such as the return loss, the specific absorption rate (SAR), and the radiation pattern within skin and muscle-fat-skin tissues are evaluated for the designed antenna. The gain of the proposed antenna is 3.2 dBi at 2.4 GHz and 4.7 dBi at 5.8 GHz; also the averaged SAR of the antenna in human body tissue is found to be well below the legally allowed limit at both frequency bands. The link budget shows the received power at the distance of 25 cm at 2.4 GHz and 5.8 GHz are around 0.4 mW and 0.04 mW, which can empower the DBS implant. The large operational bandwidth, the physical compactness, and the efficiency in wireless signal reception make this antenna suitable in being used in implanted biomedical devices such as DBS pulse generators. Sara Manafi and Hai Deng Copyright © 2014 Sara Manafi and Hai Deng. All rights reserved. Bistatic Scattering due to Hydrometeors on Cochannel Intersystem Communication Links over a Subtropical Path Thu, 30 Oct 2014 08:09:46 +0000 The performance of fixed satellite systems in the shared frequency band depends on the tolerance level of interference between them. Interference disturbs the functionality of the ground station and causes signal degradation. The knowledge of interference level must therefore be known for an optimal satellite design. In this work, we evaluate interference due to hydrometeors for a situation in which a satellite downlink signal is affected by the signal from a terrestrial microwave network operating at the same frequency as the satellite system in a subtropical station: Durban, South Africa. The evaluation of the transmission loss is based on the modified 3D bistatic radar equation and the exponential rain cell model for the scattering. The results of intersystem interference for different station separation over frequencies variation, terrestrial antenna gains, and exceedance probabilities are presented. The effect of the additional rain attenuation on the satellite signals is also examined. The results point out to some remarkable attenuation differences between the effective transmission loss and the transmission loss statistics for small time unavailability at the frequencies considered in this work. This could be detrimental in link budget design if overlooked. P. A. Owolawi and T. Wallingo Copyright © 2014 P. A. Owolawi and T. Wallingo. All rights reserved. Reduction of the In-Band RCS of Microstrip Patch Antenna by Using Offset Feeding Technique Wed, 29 Oct 2014 12:17:58 +0000 This paper presents a method for implementing a low in-band scattering design for microstrip patch antennas based on the analysis of structural mode scattering and radiation characteristics. The antenna structure is first designed to have the lowest structural mode scattering in a desired frequency band. The operating frequency band of the antenna is then changed to coincide with that of the lowest structural mode scattering by adjusting the feed position on the antenna (offset feeding) to achieve an antenna with low in-band radar cross section (RCS). In order to reduce the level of cross polarization of the antenna caused by offset feeding, symmetry feeding structures for both single patch antennas and two-patch arrays are proposed. Examples that show the efficiency of the method are given, and the results illustrate that the in-band RCS of the proposed antennas can be reduced by as much as 17 dBsm for plane waves impinging from the normal direction compared to patch antennas fed by conventional methods. Weiwei Xu, Junhong Wang, Meie Chen, Zhan Zhang, and Zheng Li Copyright © 2014 Weiwei Xu et al. All rights reserved. Erratum to “Joint Delay Doppler Probability Density Functions for Air-to-Air Channels” Tue, 28 Oct 2014 14:23:50 +0000 Michael Walter, Dmitriy Shutin, and Uwe-Carsten Fiebig Copyright © 2014 Michael Walter et al. All rights reserved. Analysis of a Compact and Superdirective Metamaterial-Inspired Monopole Antenna Tue, 28 Oct 2014 00:00:00 +0000 The directivity of a metamaterial-inspired compact (0.145λ0) monopole antenna was investigated. The proposed structure is composed of a split-ring resonator (SRR) parasitic element placed in the vicinity of a monopole antenna. Two configurations denoted by A1 and A2 were considered depending on the position of the slot in the SRR element. By analyzing simulated and measured results, the superdirectivity (7.5 dBi for A1 and 9 dBi for A2) of the structure was discussed. It is found that the monopole-SRR and/or ground plane-SRR coupling effects may be responsible for the superdirectivity of the structure. Saber Dakhli, Hatem Rmili, Kourosh Mahdjoubi, Jean-Marie Floc’h, and Fethi Choubani Copyright © 2014 Saber Dakhli et al. All rights reserved. Outage Probability of Dual-Hop Multiple Antenna Relay Systems with Interference at the Relay and Destination Mon, 27 Oct 2014 00:00:00 +0000 This paper analyzes the outage performance of a dual-hop relaying system in which the relay is equipped with multiple antennas, while the source and destination have a single antenna. New exact closed-form expressions for the outage probability of both the amplify-and-forward (AF) and the decode-and-forward (DF) relaying systems are derived, assuming that the relay and destination are impaired by cochannel interferers and additive white Gaussian noise (AWGN). Numerical results are presented to verify the theoretical analysis. Mengmeng Liu, Jianhua Zhang, and Ping Zhang Copyright © 2014 Mengmeng Liu et al. All rights reserved. Synthesis of Phase-Only Reconfigurable Linear Arrays Using Multiobjective Invasive Weed Optimization Based on Decomposition Mon, 20 Oct 2014 06:22:53 +0000 Synthesis of phase-only reconfigurable array aims at finding a common amplitude distribution and different phase distributions for the array to form different patterns. In this paper, the synthesis problem is formulated as a multiobjective optimization problem and solved by a new proposed algorithm MOEA/D-IWO. First, novel strategies are introduced in invasive weed optimization (IWO) to make original IWO fit for solving multiobjective optimization problems; then, the modified IWO is integrated into the framework of the recently well proved competitive multiobjective optimization algorithm MOEA/D to form a new competitive MOEA/D-IWO algorithm. At last, two sets of experiments are carried out to illustrate the effectiveness of MOEA/D-IWO. In addition, MOEA/D-IWO is compared with MOEA/D-DE, a new version of MOEA/D. The comparing results show the superiority of MOEA/D-IWO and indicate its potential for solving the antenna array synthesis problems. Yan Liu, Yong-Chang Jiao, Ya-Ming Zhang, and Yan-Yan Tan Copyright © 2014 Yan Liu et al. All rights reserved. A Generalized Approach for Computation of Near Field Radiation Pattern of an Antenna Sun, 19 Oct 2014 09:44:39 +0000 A generalized procedure in the form of an analytical formulation for the determination of radiation pattern of an antenna at any arbitrary distance which covers the near field as well as far field is presented in this paper. With the prior knowledge of either the current or field distribution on the radiating aperture, the proposed near field analysis is generic and can be applied for wide variety of antenna elements. The underlying principle of the generalized procedure is tantamount to considering the radiating aperture as an array of point electric and magnetic dipoles. The validity and novelty of the proposed new approach have been substantiated considering an open ended circular cylindrical waveguide and a conical horn as case studies and treating the far field as a special case of near field with pertinent distance criterion. The effect of change in the distance of observation ranging from reactive near field to far field on the radiation patterns of these antennas has also been discussed. The simulation studies reveal that the depicted normalized phase patterns of both the circular waveguide and conical horn follow the changes in the profile of the corresponding amplitude patterns. Preetham Shankpal, Varun Arur, Govind Kadambi, and James Shuttleworth Copyright © 2014 Preetham Shankpal et al. All rights reserved. An Improved Chaos Genetic Algorithm for T-Shaped MIMO Radar Antenna Array Optimization Tue, 14 Oct 2014 10:49:48 +0000 In view of the fact that the traditional genetic algorithm easily falls into local optimum in the late iterations, an improved chaos genetic algorithm employed chaos theory and genetic algorithm is presented to optimize the low side-lobe for T-shaped MIMO radar antenna array. The novel two-dimension Cat chaotic map has been put forward to produce its initial population, improving the diversity of individuals. The improved Tent map is presented for groups of individuals of a generation with chaos disturbance. Improved chaotic genetic algorithm optimization model is established. The algorithm presented in this paper not only improved the search precision, but also avoids effectively the problem of local convergence and prematurity. For MIMO radar, the improved chaos genetic algorithm proposed in this paper obtains lower side-lobe level through optimizing the exciting current amplitude. Simulation results show that the algorithm is feasible and effective. Its performance is superior to the traditional genetic algorithm. Xin Fu, Xianzhong Chen, Qingwen Hou, Zhengpeng Wang, and Yixin Yin Copyright © 2014 Xin Fu et al. All rights reserved. Radiation Characteristic Improvement of X-Band Slot Antenna Using New Multiband Frequency-Selective Surface Tue, 14 Oct 2014 08:18:23 +0000 A new configuration of frequency-selective surfaces (FSSs) is designed and presented with multiresonance characteristics which covers all of the frequency domain of X-band from 8 to 12 GHz. The proposed FSS comprises three conductor-based split ring resonators, connected together. In this design, two unit cells of the FSS with different lengths are employed side by side to design the FSS. The FSS is used to enhance the gain of the new designed triangle slot antenna at X-band. The proposed FSS is analyzed by using reflected-wave unit-cell box method. The single, double, and array of the FSS cells are studied. Next, the designed FSS along with the antenna is analyzed. The measurement and simulated results of the impedance and radiation characteristics, especially the increment of the gain, are presented. Elham Moharamzadeh Copyright © 2014 Elham Moharamzadeh. All rights reserved. Optimized Wideband Impedance Matching Balun for Conducting Two-Arm Antennas Tue, 14 Oct 2014 07:45:10 +0000 A split coaxial balun with a step transition of the inner conductor diameter is introduced to satisfy impedance matching between unbalanced feeder and balanced antennas. The location of the step transition along the axis of the balun and the diameter change are two dimensional parameters that are not present in the conventional split coaxial balun. These additional parameters, together with the double slot width, provide more flexibility to design the balun for better impedance matching. The effects of the three dimensional parameters on the input impedance seen at the (unbalanced) coaxial line side of the balun are investigated when it is terminated with specific lumped impedance at its (balanced) split side. An optimization procedure is introduced to arrive at the balun dimensional parameters to give the best matching with specific load impedance. The proposed balun is designed to feed (balanced) two-arm antennas such as the dipole and the bowtie antenna from 50 Ω-coaxial line. The electromagnetic simulation shows that the proposed balun results in a perfect impedance matching. A comparison with the performance of the conventional split balun used to feed a dipole antenna shows that the balun proposed in the present paper gives a much lower value of the return loss at the design frequency and a wider bandwidth for VSWR ≤ 1.5. The simulation results obtained using the MoM are compared with experimental measurements showing good agreement. Khalid F. A. Hussein Copyright © 2014 Khalid F. A. Hussein. All rights reserved. Two-Element Tapered Slot Antenna Array for Terahertz Resonant Tunneling Diode Oscillators Tue, 14 Oct 2014 07:38:38 +0000 Two-element tapered slot antenna (TSA) array for terahertz (THz) resonant tunneling diode (RTD) oscillators is proposed in this paper. The proposed TSA array has the advantages of both the high directivity and high gain at the horizontal direction and hence can facilitate the horizontal communication between the RTD oscillators and other integrated circuit chips. A MIM (metal-insulator-metal) stub with a T-shaped slot is used to reduce the mutual coupling between the TSA elements. The validity and feasibility of the proposed TSA array have been simulated and analyzed by the ANSYS/ANSOFT’s High Frequency Structure Simulator (HFSS). Detailed modeling approaches and theoretical analysis of the proposed TSA array have been fully addressed. The simulation results show that the mutual coupling between the TSA elements is reduced below −40 dB. Furthermore, at 500 GHz, the directivity, the gain, and the half power beam width (HPBW) at the E-plane of the proposed TSA array are 12.18 dB, 13.09 dB, and 61°, respectively. The proposed analytical method and achieved performance are very promising for the antenna array integrated with the RTD oscillators at the THz frequency and could pave the way to the design of the THz antenna array for the RTD oscillators. Jianxiong Li, Yunxiang Li, Weiguang Shi, Haolin Jiang, and Luhong Mao Copyright © 2014 Jianxiong Li et al. All rights reserved. Miniaturized Antenna Solution Based on Lossy Planar Microresonators to Conjointly Control Radiation and Selectivity Mon, 13 Oct 2014 13:21:15 +0000 We propose a new method to design miniaturized compact antennas, in which it is possible to control conjointly the radiation efficiency and the bandwidth selectivity of the antenna. And this method has been validated by the realization of prototypes based on planar resonators. The geometry of these resonators has been chosen because their unloaded quality factor can be controlled and is mainly dependent on radiation loss. In the first time, a filter with a significant potential to radiation has been realized by choosing suitable miniaturized resonators. An antenna, based on the same structure, in which the output of the filter was removed (load by air resistance) can be obtained. Modification of the quality factor of each resonator is necessary to take into account the change of the load value from the previous filter to the final structure. The position and the quality factor of the resonators are determined by a filter design concept to obtain a specific frequency response in which each resonator is a basic radiation element. Load of the antenna is ultimately a distributed load constituted by the parallel contributions of each resonators to radiation loss. In other words such an antenna can also be called radiating filter. Biyun Ma, Anne Chousseaud, and Serge Toutain Copyright © 2014 Biyun Ma et al. All rights reserved. Model-Switched Beamformer with Large Dynamic Range Mon, 13 Oct 2014 10:03:29 +0000 The strong desired signal will be mitigated due to “self-nulling” for the adaptive beamformer, even if the array calibration is used. The proposed methodology switches the models between phased array and adaptive array. In general, the system utilizes Frost adaptive beamforming. However, it will be switched to phased array if the “self-nulling” appears. According to the estimation of the array pattern at the direction of desired signal, we can determine if the “self-nulling” happens. The new approach is much easier to implement compared with the various robust beamforming algorithms. Zeng Hao, Xing Qian, Yang Qingkun, and Feng Linfeng Copyright © 2014 Zeng Hao et al. All rights reserved. Impact of Dielectric Constant on Embedded Antenna Efficiency Mon, 13 Oct 2014 08:54:42 +0000 The impact of dielectric constant on radiation efficiency of embedded antenna located inside human body or another liquid environment is investigated both analytically and numerically. Our research is analysed and simulated at 403 MHz in the MedRadio band (401–406 MHz) and within a block of 2/3 human muscle phantom. Good agreement is achieved between analysis and simulation results. This work provides a guidance in selecting insulator for embedded antennas. Van Thuan Nguyen and Chang Won Jung Copyright © 2014 Van Thuan Nguyen and Chang Won Jung. All rights reserved. Frequency-Dependent FDTD Algorithm Using Newmark’s Method Mon, 13 Oct 2014 08:04:38 +0000 According to the characteristics of the polarizability in frequency domain of three common models of dispersive media, the relation between the polarization vector and electric field intensity is converted into a time domain differential equation of second order with the polarization vector by using the conversion from frequency to time domain. Newmark βγ difference method is employed to solve this equation. The electric field intensity to polarizability recursion is derived, and the electric flux to electric field intensity recursion is obtained by constitutive relation. Then FDTD iterative computation in time domain of electric and magnetic field components in dispersive medium is completed. By analyzing the solution stability of the above differential equation using central difference method, it is proved that this method has more advantages in the selection of time step. Theoretical analyses and numerical results demonstrate that this method is a general algorithm and it has advantages of higher accuracy and stability over the algorithms based on central difference method. Bing Wei, Le Cao, Fei Wang, and Qian Yang Copyright © 2014 Bing Wei et al. All rights reserved. Simulations and Measurements of Electric Fields Emitted from a LTE Base Station in an Urban Area Mon, 13 Oct 2014 07:37:28 +0000 Radiation patterns emitted from a long-term evolution (LTE) base station antenna were first simulated by the finite-difference time domain (FDTD) method. The validity of simulation results of radiation patterns was further checked by measurement data. After validating the accuracy of the FDTD method, electric fields at 123 test sites around a LTE base station in an urban area of Taipei City were simulated. Simulated electric fields were also validated by comparison with measured data obtained by a high frequency selective radiation meter with an isotropic E-field probe. Simulated and measured electric fields are in the range of 0.104–1.182 and 0.098–1.179 V/m at 1795 MHz, respectively. From obtained electric field strengths, it is ensured that the urban area is a good signal environment. The maximum power density emitted from the LTE base station is about mW/cm2 and is thus far below the safety standard value of 1.197 mW/cm2 for human exposure to RF radiation at 1795 MHz. Hsing-Yi Chen and Tsung-Han Lin Copyright © 2014 Hsing-Yi Chen and Tsung-Han Lin. 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.