International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. A CPW-Fed Monopole Antenna with Double Rectangular Rings and Vertical Slots in the Ground Plane for WLAN/WiMAX Applications Wed, 01 Jul 2015 09:40:12 +0000 http://www.hindawi.com/journals/ijap/2015/165270/ A compact triple-band monopole antenna consisting of double rectangular rings and vertical slots cut into the ground is proposed for WLAN and WiMAX operations. The antenna has a compact size of 27.1 × 38.8 × 1.6 mm3, with simulated and measured impedance bandwidths of 2.37~2.81, 3.21~3.82, and 4.61~6.34 GHz with a reflection coefficient of less than −10 dB. The antenna also exhibits an almost omnidirectional radiation pattern and stable gain levels in the triple bands. The characteristics of the proposed antenna have been investigated using the numerical simulations and experiments. Sangjin Jo, Hyunjin Choi, Jaehyuk Lim, Beomsoo Shin, Sangyeol Oh, and Jaehoon Lee Copyright © 2015 Sangjin Jo et al. All rights reserved. Modified Fruit Fly Optimization Algorithm for Analysis of Large Antenna Array Mon, 29 Jun 2015 12:09:40 +0000 http://www.hindawi.com/journals/ijap/2015/124675/ This research paper deals with the optimization of a large antenna array for maximum directivity using a modified fruit fly optimization algorithm (MFOA) with random search of two groups of swarm and adaptive fruit fly swarm population size. The MFOA is utilized to determine three nonlinear mathematical test functions, analysis of the optimal number of elements and optimal element spacing of the large antenna array, and analysis of nonuniform amplitude of antenna array. The numerical results demonstrate that the MFOA is effective in solving all test function and electromagnetic problems. The advantages of the proposed algorithm are ease of implementation, large search range, less processing time, and reduced memory requirement. Nattaset Mhudtongon, Chuwong Phongcharoenpanich, and Supakit Kawdungta Copyright © 2015 Nattaset Mhudtongon et al. All rights reserved. Wideband, Multiband, Tunable, and Smart Antenna Systems for Mobile and UWB Wireless Applications 2014 Sun, 28 Jun 2015 07:11:05 +0000 http://www.hindawi.com/journals/ijap/2015/536031/ Renato Cicchetti, Antonio Faraone, Diego Caratelli, and Massimiliano Simeoni Copyright © 2015 Renato Cicchetti et al. All rights reserved. Measurements of Building Transmission Loss and Delay Spread at 2.5 GHz Thu, 25 Jun 2015 11:39:04 +0000 http://www.hindawi.com/journals/ijap/2015/683941/ This paper presents the results of measurements of signal transmission loss at 2.5 GHz through 10 urban buildings. This allows the characterization of different types of buildings by effective attenuation constants and consideration of the contribution of the transmitted signal in microcell coverage predictions. Power delay profiles (PDPs) of the received signal were also measured and used to determine the time dispersion parameters of the channel, including the mean excess delay and the rms delay spread. L. H. Gonsioroski and L. da Silva Mello Copyright © 2015 L. H. Gonsioroski and L. da Silva Mello. All rights reserved. An EM Modeling for Rescue System Design of Buried People Wed, 24 Jun 2015 12:12:00 +0000 http://www.hindawi.com/journals/ijap/2015/465651/ The development of a rescue system for buried persons is a subject of growing importance in case of occurrence of natural disasters such as earthquake, landslides, or avalanches. In this paper a fully analytical model has been developed to get some fundamental a priori design characteristics. The proposed system is based on the detection of the victim movements due to its respiratory activity: in particular, when an electromagnetic (EM) wave impinges on a human body, the analysis of the reflected wave parameters such as amplitude, frequency, phase, or delay time allows for the detection of the breathing frequency. The model is simple on purpose because the great uncertainty concerning the characterization of many environmental parameters of a general situation makes a very detailed model useless. However, it is accurate enough to provide useful information about system design, filling the gap in the literature concerning the electromagnetic formulation of such kinds of problems. A system prototype was built using laboratory equipment to experimentally validate the model, and subsequently breathing frequency measurements were carried on, both in a lossless laboratory environment and in a lossy realistic scenario. A. De Leo, V. Petrini, P. Russo, L. Scalise, V. Di Mattia, Valter Mariani Primiani, and G. Cerri Copyright © 2015 A. De Leo et al. All rights reserved. Obtaining Ionospheric Conditions according to Data of Navigation Satellites Wed, 24 Jun 2015 10:30:32 +0000 http://www.hindawi.com/journals/ijap/2015/804791/ Defining ionospheric conditions, the deviation of the observational value of the total electron content TEC(obs), measured by means of navigation satellites, from a median is a bench mark. According to more than 40 ionospheric stations during April 2014 it is shown that synchronism of change of deviations of TEC and critical frequency foF2 of the ionosphere is kept under quiet and moderate disturbed conditions. This fact allows to use a median of the equivalent slab thickness τ(med) as a reliable calibration factor to calculate foF2 from TEC(obs). The efficiency coefficient of joint use of τ(med) and TEC(obs) changes from 1.5 to 4 with average value 2.2 across the globe. The highest coefficient corresponds to middle latitudes, however the estimations obtained for high- and low-latitude areas indicate possibility to use τ(med) and TEC(obs) in these areas. Olga Maltseva and Natalia Mozhaeva Copyright © 2015 Olga Maltseva and Natalia Mozhaeva. All rights reserved. Comparative Study of Crosstalk Reduction Techniques in RF Printed Circuit Board Using FDTD Method Tue, 23 Jun 2015 08:56:00 +0000 http://www.hindawi.com/journals/ijap/2015/294590/ Miniaturization of the feature size in modern electronic circuits results from placing interconnections in close proximity with a high packing density. As a result, coupling between the adjacent lines has increased significantly, causing crosstalk to become an important concern in high-performance circuit design. In certain applications, microstriplines may be used in printed circuit boards for propagating high-speed signals, rather than striplines. Here, the electromagnetic coupling effects are analyzed for various microstrip transmission line structures, namely, microstriplines with a guard trace, double stub microstriplines, and parallel serpentine microstriplines using the finite-difference time-domain method. The numerical results are compared with simulation results, where the variants are simulated using an Ansoft high-frequency structure simulator. The analysis and simulation results are experimentally validated by fabricating a prototype and establishing a good correspondence between them. Numerical results are compared with simulation and experimental results, showing that double stub microstriplines reduce the far end crosstalk by 7 dB and increase the near end crosstalk by about 2 dB compared with the parallel microstriplines. Parallel serpentine microstriplines reduce the far end crosstalk by more than 10 dB and also reduce more than 15 mV of peak far end crosstalk voltage, compared with parallel microstriplines. Rajeswari Packianathan and Raju Srinivasan Copyright © 2015 Rajeswari Packianathan and Raju Srinivasan. All rights reserved. Improvement on a 2 × 2 Elements High-Gain Circularly Polarized Antenna Array Mon, 22 Jun 2015 09:12:46 +0000 http://www.hindawi.com/journals/ijap/2015/252717/ A novel antipodal Vivaldi antenna with tapering serrated structure at the edges is proposed. Compared with traditional Vivaldi antennas without serrated structure, the gain of the designed antenna is significantly improved in the desired frequency band (4.5–7.5 GHz). In addition, a 2 × 2 Vivaldi antenna array with an orthorhombic structure is designed and fabricated to achieve a circular polarization (CP) characteristic. With this configuration, the 3 dB axial ratio bandwidth of the array reaches about 42% with respect to the center frequency of 6 GHz and a high gain is achieved as well. The novel Vivaldi antenna and CP antenna array both have ultrawide band (UWB) and high-gain characteristics, which may be applied to the field of commercial communication, remote sensing, and so forth. C. Liu, A. Yan, C. Yu, and T. Xu Copyright © 2015 C. Liu et al. All rights reserved. A Compact Frequency Reconfigurable Antenna for LTE Mobile Handset Applications Sun, 21 Jun 2015 09:34:54 +0000 http://www.hindawi.com/journals/ijap/2015/764949/ A compact (8 × 62 × 5 mm3; 2.48 cc) frequency reconfigurable antenna that uses electrical switching with PIN diodes is proposed for the low frequency LTE band (699 MHz–862 MHz), high frequency LTE band (2496 MHz–2690 MHz), GSM850/900 bands (824 MHz–960 MHz), and DCS/PCS/WCDMA bands (1710 MHz–2170 MHz). The penta-band PIFA is first designed for GSM850/900/DCS/PCS/WCDMA bands by using two slits and ground pins within a limited antenna volume (8 × 54.6 × 5 mm3; 2.18 cc). The frequency reconfigurable antenna based on this penta-band PIFA is thus proposed to additionally cover all LTE bands. The proposed antenna has two PIN diodes with an optimal location. For State 1 (PIN diode 1: ON state, PIN diode 2: OFF state), the proposed antenna covers the low frequency LTE band, DCS/PCS/WCDMA bands, and high frequency LTE band. For State 2 (PIN diode 1: OFF state, PIN diode 2: ON state), the antenna covers the GSM850/900 bands. Simulated and measured results show that the total efficiency of the proposed antenna was greater than 40% for all operating frequency bands. Munyong Choi, Hyunho Wi, Byeonggwi Mun, Yonghyun Yoon, Hyunwoo Lee, and Byungje Lee Copyright © 2015 Munyong Choi et al. All rights reserved. An Optimized Parallel FDTD Topology for Challenging Electromagnetic Simulations on Supercomputers Mon, 15 Jun 2015 14:09:38 +0000 http://www.hindawi.com/journals/ijap/2015/690510/ It may not be a challenge to run a Finite-Difference Time-Domain (FDTD) code for electromagnetic simulations on a supercomputer with more than 10 thousands of CPU cores; however, to make FDTD code work with the highest efficiency is a challenge. In this paper, the performance of parallel FDTD is optimized through MPI (message passing interface) virtual topology, based on which a communication model is established. The general rules of optimal topology are presented according to the model. The performance of the method is tested and analyzed on three high performance computing platforms with different architectures in China. Simulations including an airplane with a 700-wavelength wingspan, and a complex microstrip antenna array with nearly 2000 elements are performed very efficiently using a maximum of 10240 CPU cores. Shugang Jiang, Yu Zhang, Zhongchao Lin, and Xunwang Zhao Copyright © 2015 Shugang Jiang et al. All rights reserved. Two-Dimensional DOA Estimation in Compressed Sensing with Compressive-Reduced Dimension--MUSIC Mon, 15 Jun 2015 08:39:02 +0000 http://www.hindawi.com/journals/ijap/2015/792181/ This paper presents a novel two-dimensional (2D) direction of arrival (DOA) estimation method in compressed sensing (CS) to remove the estimation failure problem and achieve superior performance. The proposed method separates the steering vector into two parts to construct two corresponding noise subspaces by introducing electric angles. Then, electric angles are estimated based on the constructed noise subspaces. In order to estimate the azimuth and elevation angles in terms of estimates of electric angles, arc-tangent operations are exploited. The arc-tangent is a one-to-one function and allows the value of the argument to be larger than unity so that the proposed method never fails. The proposed method can avoid pair matching to reduce the computational complexity and extend the number of snapshots to improve performance. Simulation results show that the proposed method can avoid estimation failure occurrence and has superior performance as compared to existing methods. Weijian Si, Xinggen Qu, Lutao Liu, and Zhiyu Qu Copyright © 2015 Weijian Si et al. All rights reserved. Capacitively Loaded Loop-Based Antennas with Reconfigurable Radiation Patterns Mon, 15 Jun 2015 06:22:48 +0000 http://www.hindawi.com/journals/ijap/2015/523198/ A class of metamaterial-inspired antennas having reconfigurable radiation patterns is proposed. They consist of a driven monopole antenna with one- and two-capacitively loaded loop (CLL), near field resonant parasitic elements. Two configurations are studied by considering the state of these CLL elements as being either open or closed configurations. Simulation results explain the design features and demonstrate that the structure can change its beam direction simply by controlling the switched states. Two prototypes with one- and two-CLL elements were fabricated and tested. The measured impedance mismatch and radiation pattern results are presented and compared to the corresponding simulated values. Saber Dakhli, Hatem Rmili, Jean-marie Floc’h, Muntasir Sheikh, Kourosh Mahdjoubi, Fethi Choubani, and Richard W. Ziolkowski Copyright © 2015 Saber Dakhli et al. All rights reserved. A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations Sun, 14 Jun 2015 06:46:44 +0000 http://www.hindawi.com/journals/ijap/2015/190607/ The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading. Taimoor Abbas, Katrin Sjöberg, Johan Karedal, and Fredrik Tufvesson Copyright © 2015 Taimoor Abbas et al. All rights reserved. Multiantenna Spectrum Sensing in the Presence of Multiple Primary Users over Fading and Nonfading Channels Thu, 11 Jun 2015 11:30:17 +0000 http://www.hindawi.com/journals/ijap/2015/165935/ The basis of this paper is Wei and Tirkkonen, 2012, in which expressions for the key performance metrics of the sphericity test applied to the multiantenna cooperative spectrum sensing of multiple primary transmitters in cognitive radio networks over nonfading channels are provided. The false alarm and the detection probabilities were derived in Wei and Tirkkonen, 2012, based on approximations obtained by matching the moments of the test statistics to the Beta distribution. In this paper we show that the model adopted in Wei and Tirkkonen, 2012, does not apply directly to fading channels, yet being considerably inaccurate for some system parameters and channel conditions. Nevertheless, we show that the original expressions from Wei and Tirkkonen, 2012, can be simply and accurately applied to a modified model that considers fixed or time-varying channels with any fading statistic. We also analyze the performance of the sphericity test and other competing detectors with a varying number of primary transmitters, considering different situations in terms of the channel gains and channel dynamics. Based on our results, we correct several interpretations from Wei and Tirkkonen, 2012, in what concerns the performance of the detectors, both over a fixed-gain additive white Gaussian noise channel and over a time-varying Rayleigh fading channel. Dayan Adionel Guimarães, Rausley Adriano Amaral de Souza, and Guilherme Pedro Aquino Copyright © 2015 Dayan Adionel Guimarães et al. All rights reserved. Fast Integral Equation Solution of Scattering of Multiscale Objects by Domain Decomposition Method with Mixed Basis Functions Thu, 11 Jun 2015 07:18:54 +0000 http://www.hindawi.com/journals/ijap/2015/563436/ Nonconformal nonoverlapping domain decomposition method (DDM) with mixed basis functions is presented to realize fast integral equation solution of electromagnetic scattering of multiscale objects. The original multiscale objects are decomposed into several closed subdomains. The higher order hierarchical vector basis functions are used in the electrically large smooth subdomains to significantly reduce the number of unknowns, while traditional Rao-Wilton-Glisson basis functions are used for subdomains with tiny structures. A well-posed matrix is successfully derived by the present DDM. Besides, the nonconformal property of DDM allows flexible mesh generation for complicated objects. Numerical results are presented to validate the proposed method and illustrate its advantages. Ran Zhao, Hua Peng Zhao, Zai-ping Nie, and Jun Hu Copyright © 2015 Ran Zhao et al. All rights reserved. MIMO SAR Using Orthogonal Coding: Design, Performance Analysis, and Verifications Wed, 10 Jun 2015 12:29:48 +0000 http://www.hindawi.com/journals/ijap/2015/629506/ Multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) is a promising technology in radar imaging which provides a better balance of azimuth resolution and swath width compared with traditional single-input single-output (SISO) SAR. It has the potential to help scientists and engineers to design ambitious SAR system with higher resolution and wider swath. This paper studies the principle of MIMO SAR using orthogonal coding waveform and then provides the performance analysis in resolution and swath width. By using orthogonal coding waveform, lower channel interference is obtained, which makes MIMO SAR achieve wider unambiguous range swath and lower azimuth ambiguity. Simulations are carried out by means of the system parameters of real spaceborne SAR platform. A ground-based MIMO SAR imaging system with up and down chirp modulation is also designed. The performances of MIMO SAR and SISO SAR are compared, and the validity and advantage of MIMO SAR are verified. Yueguan Lin, Yida Fan, Chenglong Jiang, Zhiqiang Wang, and Weizeng Shao Copyright © 2015 Yueguan Lin et al. All rights reserved. Sidelobe Suppression with Null Steering by Independent Weight Control Wed, 10 Jun 2015 11:17:01 +0000 http://www.hindawi.com/journals/ijap/2015/136826/ A uniform linear array of antenna elements can steer up to nulls. In situations where less than nulls are required to be steered, the existing algorithms have no criterion to utilize the remaining weights for sidelobe suppression. This work combines sidelobe suppression capability with null steering by independent weight control. For this purpose, the array factor is transformed as the product of two polynomials. One of the polynomials is used for null steering by independent weight control, while the second one is for sidelobe suppression whose coefficients or weights are determined by using convex optimization. Finally, a new structure is proposed to incorporate the product of two polynomials such that sidelobe suppression weights are decoupled from those of null steering weights. Simulation results validate the effectiveness of the proposed scheme. Zafar-Ullah Khan, Aqdas Naveed Malik, Fawad Zaman, Syed Azmat Hussain, and Abdul-Rehman Khan Copyright © 2015 Zafar-Ullah Khan et al. All rights reserved. Designs and Performance Characteristics of Coated Nanotoroid Antennas Mon, 08 Jun 2015 12:57:43 +0000 http://www.hindawi.com/journals/ijap/2015/345137/ The electromagnetic properties of a toroidal coated nanoparticle (T-CNP) antenna with an active core (doped with rare earth erbium Er3+ ions) are investigated. It is demonstrated that the active T-CNP acts as a strong dipole radiator at its resonance frequency when it is excited by a plane wave or an electric Hertzian dipole (EHD) radiating element. It is shown that in comparison to being a passive structure, the plane wave scattering cross section of the T-CNP can be increased by nearly 108 dBsm at its resonance frequency when it is active. Moreover, it is further demonstrated that the maximum peak of the power radiated by an EHD element in the presence of a properly designed active T-CNP is more than 120 dB over its value when radiating in free space; that is, its Purcell factor is 1012. Sami Ur Rehman, Junping Geng, Richard W. Ziolkowski, Ying Wang, Xianling Liang, and Ronghong Jin Copyright © 2015 Sami Ur Rehman et al. All rights reserved. Novel Base Station MIMO Antennas with Enhanced Spectral Efficiencies Using Angular Reuse Thu, 04 Jun 2015 13:09:14 +0000 http://www.hindawi.com/journals/ijap/2015/150301/ The true polarization diversity (TPD) technique is combined with the spatial diversity technique in novel MIMO antenna array geometries with a large number of elements. The use of a large number of elements requires some angular reuse within the array for polarization diversity. With designs compatible with existing base station antenna array configurations, the novel geometries with combining diversity schemes are shown to be able to achieve near the maximum spectral efficiencies. True polarization diversity (TPD) schemes are found to be an excellent complement to more conventional spatial diversity schemes for obtaining optimum MIMO array performance in base station antennas. Miguel Mora-Andreu and David A. Sánchez-Hernández Copyright © 2015 Miguel Mora-Andreu and David A. Sánchez-Hernández. All rights reserved. An Efficient Full-Wave Electromagnetic Analysis for Capacitive Body-Coupled Communication Thu, 04 Jun 2015 11:16:07 +0000 http://www.hindawi.com/journals/ijap/2015/245621/ Measured propagation loss for capacitive body-coupled communication (BCC) channel (1 MHz to 60 MHz) is limitedly available in the literature for distances longer than 50 cm. This is either because of experimental complexity to isolate the earth-ground or design complexity in realizing a reliable communication link to assess the performance limitations of capacitive BCC channel. Therefore, an alternate efficient full-wave electromagnetic (EM) simulation approach is presented to realistically analyze capacitive BCC, that is, the interaction of capacitive coupler, the human body, and the environment all together. The presented simulation approach is first evaluated for numerical/human body variation uncertainties and then validated with measurement results from literature, followed by the analysis of capacitive BCC channel for twenty different scenarios. The simulation results show that the vertical coupler configuration is less susceptible to physiological variations of underlying tissues compared to the horizontal coupler configuration. The propagation loss is less for arm positions when they are not touching the torso region irrespective of the communication distance. The propagation loss has also been explained for complex scenarios formed by the ground-plane and the material structures (metals or dielectrics) with the human body. The estimated propagation loss has been used to investigate the link-budget requirement for designing capacitive BCC system in CMOS sub-micron technologies. Muhammad Irfan Kazim, Muhammad Imran Kazim, and J. Jacob Wikner Copyright © 2015 Muhammad Irfan Kazim et al. All rights reserved. Study of the Colocated Dual-Polarized MIMO Capacity Composed of Dipole and Loop Antennas Wed, 03 Jun 2015 07:27:07 +0000 http://www.hindawi.com/journals/ijap/2015/412127/ The colocated dual-polarized dipole (DPD) and dual-polarized loop (DPL) MIMO channel performances are compared. Computation results show that, for the ideal electric and magnetic dipoles, the dual-polarized MIMO systems have identical channel capacity. But the contour plots of the capacity gain of the realistic DPD and DPL are different, due to the difference in antenna patterns. The cumulative distribution function (CDF) of the capacity gain in the two-mirror (TM) channel shows that, for small distance, the capacity gain obtained by the DPD is obviously smaller than that of the DPL, but, with the increase of the distance, the difference gets smaller. A DPL with low mutual coupling is fabricated. Measured results show that high MIMO capacities can be obtained by this DPL in both the anechoic chamber (AC) and the realistic office room. The capacity gain of the DPL antenna is 1.5–1.99, which basically coincides with the theoretical and numerical results. Furthermore, the capacity of the virtual DPL antenna with no mutual couplings is also investigated. It is shown that, in the AC, the mutual coupling will generally decrease the dual-polarized MIMO capacity; however, in the office room, the effect of mutual coupling is not always negative. Dazhi Piao, Xingning Jia, Lingyu Yang, Qingxin Guo, Yi Mao, and Zengrui Li Copyright © 2015 Dazhi Piao et al. All rights reserved. Electromagnetic Field Interference on Transmission Lines due to On-Board Antenna Sun, 31 May 2015 11:15:23 +0000 http://www.hindawi.com/journals/ijap/2015/104506/ As the available space in the board of a mobile device becomes smaller and more compact, circuit elements and transmission lines are arranged in very close proximity, especially from the antennas which are usually installed on the same board. Due to the various on-board antennas which are designed in small space, the transmission lines on the board are electromagnetically interfered, resulting in the performance degradation of the circuit. So the engineers and circuit designers should find the least interfered place for the transmission lines and components to minimize the electromagnetic interferences. This paper discusses and presents a methodology to find the least sensitive position in the induced current distribution as well as in the noise power delivered from the antenna. For this purpose some vertical, horizontal, and bent transmission lines with antenna on the same board are designed and fabricated with and without common ground, and the transferred powers to the transmission lines were measured and were also simulated using a full-wave simulator. The results predicted by the EM simulation model were successfully confirmed through the measurement of S-parameters in the experimental setup, which shows the validness of the suggested analysis method. Heekwon Lee, Soojung Ryu, Seungbae Lee, SoYoung Kim, and Wansoo Nah Copyright © 2015 Heekwon Lee et al. All rights reserved. Small-Size Seven-Band WWAN/LTE Antenna with Distributed LC Resonant Circuit for Smartphone Application Wed, 27 May 2015 09:24:53 +0000 http://www.hindawi.com/journals/ijap/2015/630674/ A compact small-size coupled-fed antenna composed of an inverted L-shaped feeding strip and a shorting strip with double branches for the WWAN/LTE bands operation in the internal smartphone application is presented. With the help of a novel distributed LC resonant circuit, the proposed antenna can not only realize the miniaturization (15 × 28 × 4 mm3) and multiband to cover 2G/3G/4G bands but also be tuned and optimized easily. The measured bandwidth with 3 : 1 VSWR is 163 MHz (804–967 MHz) at the low-band and 1615 MHz (1665–3280 MHz) at the high-band. What is more, the lowest measured efficiency in the whole frequency band is more than 52% for practical applications. The operating principles and main parameters are detailed below. And successful simulation, fabrication, and measurement of the proposed antenna are shown in this paper. Yan-Wu Liang and Hao-Miao Zhou Copyright © 2015 Yan-Wu Liang and Hao-Miao Zhou. All rights reserved. Two-Dimensional DOA Estimation for Uniform Rectangular Array Using Reduced-Dimension Propagator Method Sun, 24 May 2015 12:27:12 +0000 http://www.hindawi.com/journals/ijap/2015/485351/ A novel algorithm is proposed for two-dimensional direction of arrival (2D-DOA) estimation with uniform rectangular array using reduced-dimension propagator method (RD-PM). The proposed algorithm requires no eigenvalue decomposition of the covariance matrix of the receive data and simplifies two-dimensional global searching in two-dimensional PM (2D-PM) to one-dimensional local searching. The complexity of the proposed algorithm is much lower than that of 2D-PM. The angle estimation performance of the proposed algorithm is better than that of estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm and conventional PM algorithms, also very close to 2D-PM. The angle estimation error and Cramér-Rao bound (CRB) are derived in this paper. Furthermore, the proposed algorithm can achieve automatically paired 2D-DOA estimation. The simulation results verify the effectiveness of the algorithm. Ming Zhou, Xiaofei Zhang, Xiaofeng Qiu, and Chenghua Wang Copyright © 2015 Ming Zhou et al. All rights reserved. Numerical and Experimental Verification of a 3D Quasi-Optical System Sun, 24 May 2015 06:54:44 +0000 http://www.hindawi.com/journals/ijap/2015/595023/ A modular and efficient Gaussian beam (GB) analysis method, incorporating frame-based Gabor transformation, GB reflection, and a 3D GB diffraction technique, was developed to analyze both the reflectors and frequency selective surface (FSS) in quasi-optical (QO) system. To validate this analysis method, a 3D dual-channel QO system operating at 183 and 325 GHz was designed and tested. The proposed QO system employs two-layer structure with a FSS of perforated hexagonal array transmitting the 325 GHz signal on the top layer while diverting the 183 GHz signal to the bottom layer. Measured results of the system demonstrate that the agreement can be achieved down to −30 dB signal level for both channels in the far field pattern. The discrepancy between the calculation and measurement is within 2 dB in the main beam region (2.5 times −3 dB beamwidth), verifying the effectiveness and accuracy of the proposed method. Zejian Lu, Xiaoming Liu, Hai Wang, Xiaodong Chen, Yuan Yao, and Junsheng Yu Copyright © 2015 Zejian Lu et al. All rights reserved. Stepped Cylindrical Antenna with a Higher-Order Mode Ring Patch for Wideband Conical Radiation Pattern Thu, 21 May 2015 14:19:39 +0000 http://www.hindawi.com/journals/ijap/2015/394621/ A stepped cylindrical antenna with a higher-order mode ring patch for wideband conical radiation pattern is proposed. To accomplish a low profile with wideband conical radiation characteristics, a stepped cylindrical monopole and a TM41 higher-order mode ring patch with four shorting pins are utilized. The proposed antenna has a monopole-like radiation pattern with a wide 10-dB return loss bandwidth of 11 GHz (2 GHz–13 GHz). It can cover various wireless services, such as wireless broadband (WiBro; 2.3 GHz–2.39 GHz), wireless local area networks (WLAN; 2.4 GHz–2.484 GHz, 5.15 GHz–5.35 GHz, and 5.725 GHz–5.875 GHz), digital multimedia broadcasting (DMB; 2.63 GHz–2.655 GHz), and ultra wideband (UWB; 3.1 GHz–10.6 GHz). The antenna has a height of only 0.12λ0 at 2 GHz. Jinpil Tak, Do-Gu Kang, and Jaehoon Choi Copyright © 2015 Jinpil Tak et al. All rights reserved. Research on Polarization Cancellation of Nonstationary Ionosphere Clutter in HF Radar System Thu, 21 May 2015 13:02:23 +0000 http://www.hindawi.com/journals/ijap/2015/631217/ Oblique projection polarization filter (OPPF) can be applied as an effective approach for interference cancellation in high-frequency surface wave radar (HFSWR) and other systems. In order to suppress the nonstationary ionosphere clutter further, a novel OPPF based clutter suppressing scheme is proposed in this paper. The polarization and nonstationary characteristic of the clutter are taken into account in the algorithms referred to as range-Doppler domain polarization suppression (RDDPS) and the range-time domain polarization suppression (RTDPS) method, respectively. The RDDPS is designed for weak ionosphere clutter and implemented in the range-Doppler domain directly, whereas the RTDPS algorithm is designed to suppress the powerful ionosphere clutter with a multisegment estimation and suppression scheme. About 15–23 dB signal to interference ratio (SIR) improvement can be excepted when using the proposed method, whereas the targets can be more easily detected in the range-Doppler map. Experimental results demonstrate that the scheme proposed is effective for nonstationary ionosphere clutter and is proven to be a practical interference cancellation technique for HFSWR. Xingpeng Mao, Hong Hong, Weibo Deng, and Yongtan Liu Copyright © 2015 Xingpeng Mao et al. All rights reserved. A Butterfly-Shaped Wideband Microstrip Patch Antenna for Wireless Communication Thu, 21 May 2015 12:58:42 +0000 http://www.hindawi.com/journals/ijap/2015/328208/ A novel butterfly-shaped patch antenna for wireless communication is introduced in this paper. The antenna is designed for wideband wireless communications and radio-frequency identification (RFID) systems. Two symmetrical quasi-circular arms and two symmetrical round holes are incorporated into the patch of a microstrip antenna to expand its bandwidth. The diameter and position of the circular slots are optimized to achieve a wide bandwidth. The validity of the design concept is demonstrated by means of a prototype having a bandwidth of about 40.1%. The return loss of the butterfly-shaped antenna is greater than 10 dB between 4.15 and 6.36 GHz. The antenna can serve simultaneously most of the modern wireless communication standards. Liling Sun, Maowei He, Jingtao Hu, Yunlong Zhu, and Hanning Chen Copyright © 2015 Liling Sun et al. All rights reserved. The Application of JDL to Suppress Sea Clutter for Shipborne HFSWR Wed, 20 May 2015 09:03:28 +0000 http://www.hindawi.com/journals/ijap/2015/825350/ This paper deals with the problem of sea clutter suppression for shipborne high frequency surface wave radar (HFSWR) based on the joint domain localized (JDL) adaptive processing algorithm. The performance of the novel method is compared with 2D FFT plus digital beamforming (FFT-DBF) and orthogonal weight in different azimuths. The results based on simulated and real data show that the novel method provides higher detection performance than others. Zhenyuan Ji, Chunlei Yi, Junhao Xie, and Yang Li Copyright © 2015 Zhenyuan Ji et al. All rights reserved. Statistical Angular Resolution Limit for Ultrawideband MIMO Noise Radar Wed, 20 May 2015 08:40:59 +0000 http://www.hindawi.com/journals/ijap/2015/906313/ The two-dimensional angular resolution limit (ARL) of elevation and azimuth for MIMO radar with ultrawideband (UWB) noise waveforms is investigated using statistical resolution theory. First, the signal model of monostatic UWB MIMO noise radar is established in a 3D reference frame. Then, the statistical angular resolution limits (SARLs) of two closely spaced targets are derived using the detection-theoretic and estimation-theoretic approaches, respectively. The detection-theoretic approach is based on the generalized likelihood ratio test (GLRT) with given probabilities of false alarm and detection, while the estimation-theoretic approach is based on Smith’s criterion which involves the Cramér-Rao lower bound (CRLB). Furthermore, the relationship between the two approaches is presented, and the factors affecting the SARL, that is, detection parameters, transmit waveforms, array geometry, signal-to-noise ratio (SNR), and parameters of target (i.e., radar cross section (RCS) and direction), are analyzed. Compared with the conventional radar resolution theory defined by the ambiguity function, the SARL reflects the practical resolution ability of radar and can provide an optimization criterion for radar system design. Xiaoli Zhou, Hongqiang Wang, Yongqiang Cheng, Yuliang Qin, and Haowen Chen Copyright © 2015 Xiaoli Zhou et al. All rights reserved.