International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . 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 http://www.hindawi.com/journals/ijap/2014/150761/ 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 http://www.hindawi.com/journals/ijap/2014/383716/ 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 http://www.hindawi.com/journals/ijap/2014/308268/ 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 http://www.hindawi.com/journals/ijap/2014/806379/ 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 http://www.hindawi.com/journals/ijap/2014/370684/ 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 http://www.hindawi.com/journals/ijap/2014/630529/ 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 http://www.hindawi.com/journals/ijap/2014/958148/ 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 http://www.hindawi.com/journals/ijap/2014/631820/ 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 http://www.hindawi.com/journals/ijap/2014/321287/ 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 http://www.hindawi.com/journals/ijap/2014/748216/ 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 http://www.hindawi.com/journals/ijap/2014/847475/ 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 http://www.hindawi.com/journals/ijap/2014/802815/ 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 http://www.hindawi.com/journals/ijap/2014/625259/ 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 http://www.hindawi.com/journals/ijap/2014/758139/ 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 http://www.hindawi.com/journals/ijap/2014/216763/ 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 http://www.hindawi.com/journals/ijap/2014/147341/ 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 http://www.hindawi.com/journals/ijap/2014/302580/ 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 http://www.hindawi.com/journals/ijap/2014/317683/ 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 http://www.hindawi.com/journals/ijap/2014/690573/ 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 http://www.hindawi.com/journals/ijap/2014/847169/ 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 http://www.hindawi.com/journals/ijap/2014/412613/ 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 http://www.hindawi.com/journals/ijap/2014/297082/ 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. A Novel Broadband Printed Dipole Antenna and Its Application for TD-LTE Communications Thu, 04 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijap/2014/960963/ 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. Backtracking Search Optimization Algorithm for Synthesis of Concentric Circular Antenna Arrays Thu, 04 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijap/2014/250841/ 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. 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 http://www.hindawi.com/journals/ijap/2014/716829/ 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 http://www.hindawi.com/journals/ijap/2014/797930/ 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 http://www.hindawi.com/journals/ijap/2014/193690/ 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 http://www.hindawi.com/journals/ijap/2014/978258/ 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 http://www.hindawi.com/journals/ijap/2014/728756/ 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 http://www.hindawi.com/journals/ijap/2014/946781/ 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.