International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Evolutionary Algorithm Geometry Optimization of Optical Antennas Mon, 20 Jun 2016 15:05:35 +0000 http://www.hindawi.com/journals/ijap/2016/3156702/ Printed circuit antennas have been used for the detection of electromagnetic radiation at a wide range of frequencies that go from radio frequencies (RF) up to optical frequencies. The design of printed antennas at optical frequencies has been done by using design rules derived from the radio frequency domain which do not take into account the dispersion of material parameters at optical frequencies. This can make traditional RF antenna design not suitable for optical antenna design. This work presents the results of using a genetic algorithm (GA) for obtaining an optimized geometry (unconventional geometries) that may be used as optical regime antennas to capture electromagnetic waves. The radiation patterns and optical properties of the GA generated geometries were compared with the conventional dipole geometry. The characterizations were conducted via finite element method (FEM) computational simulations. Ramón Díaz de León-Zapata, Gabriel González, Efrén Flores-García, Ángel Gabriel Rodríguez, and Francisco Javier González Copyright © 2016 Ramón Díaz de León-Zapata et al. All rights reserved. An Efficient Plot Fusion Method for High Resolution Radar Based on Contour Tracking Algorithm Thu, 16 Jun 2016 08:14:36 +0000 http://www.hindawi.com/journals/ijap/2016/3025642/ With the development of radar system, the problem of enormous raw data has drawn much attention. A plot fusion method based on contour tracking algorithm is proposed to detect extended targets in a radar image. Firstly, the characteristic of radar image in complex environment is revealed. Then, the steps of traditional method, region growing method, and the proposed method are introduced. Meanwhile, the algorithm of tracking the contour of an extended target is illustrated in detail. It is not necessary to scan all the plots in the image, because the size of target is considered in the proposed method. Therefore, the proposed method is much more efficient than several existing methods. Lastly, the performance of several methods is tested using the raw data of two scenarios in real world. The experiment results show that the proposed method is practical and most likely to satisfy the real-time requirement in various complex environment. Bo. Yan, L. P. Xu, Kun Zhao, and J. Z. H. Yan Copyright © 2016 Bo. Yan et al. All rights reserved. A Compact MIMO Antenna with Inverted C-Shaped Ground Branches for Mobile Terminals Wed, 15 Jun 2016 10:34:03 +0000 http://www.hindawi.com/journals/ijap/2016/3080563/ A compact printed MIMO antenna for mobile terminals is presented. With two planar antenna elements, the −6 dB impedance bandwidth of 2.32 GHz (1.48–3.8 GHz) is obtained, which covers GSM 1800/1900, UMTS, WLAN, Wimax, S-band, and most of LTE bands. Each antenna element with a small occupation of 15 × 20 mm2 consists of a driven strip and a shorted strip. Two inverted C-shaped ground branches are introduced between two elements to improve the isolation. The simulated results are studied and the measured results show that high isolation of more than 18 dB at the entire operating band is achieved. Meanwhile, the impedance performance is also improved by adding the branches. Furthermore, the measured radiation performances and envelope correlation coefficient also demonstrate that the proposed antenna could be a good candidate for mobile terminals. Zixian Yang, Hongchun Yang, and Haijuan Cui Copyright © 2016 Zixian Yang et al. All rights reserved. Compact Penta-Band Dual ZOR Antenna for Mobile Applications Tue, 07 Jun 2016 08:54:17 +0000 http://www.hindawi.com/journals/ijap/2016/6461805/ A compact penta-band dual zeroth order resonator (ZOR) antenna with band-stop filter is proposed for mobile applications. The ZOR antenna is designed with modified mushroom-like structures extended on nonground region to obtain good efficiency and broad bandwidth. This modified mushroom-like structure is confirmed as double negative (DNG) transmission line by full wave simulated dispersion relation. Moreover, a bended patch and a band-stop filter (BSF) are employed to increase efficiency and bandwidth, respectively. The length of each antenna is about at the resonant frequencies of 900 MHz and 1800 MHz, respectively. The overall dimension of the antenna is 54.4 mm (length) × 4 mm (width) × 5 mm (height). The total efficiencies in low and high bands are measured more than 40% and 70%, respectively. Jae-Gon Lee, Dong-Jin Kim, and Jeong-Hae Lee Copyright © 2016 Jae-Gon Lee et al. All rights reserved. Missile-Borne SAR Raw Signal Simulation for Maneuvering Target Wed, 01 Jun 2016 11:08:08 +0000 http://www.hindawi.com/journals/ijap/2016/2598024/ SAR raw signal simulation under the case of maneuver and high-speed has been a challenging and urgent work recently. In this paper, a new method based on one-dimensional fast Fourier transform (1DFFT) algorithm is presented for raw signal simulation of maneuvering target for missile-borne SAR. Firstly, SAR time-domain raw signal model is given and an effective Range Frequency Azimuth Time (RFAT) algorithm based on 1DFFT is derived. In this algorithm, the “Stop and Go” (SaG) model is adopted and the wide radar scattering characteristic of target is taken into account. Furthermore, the “Inner Pulse Motion” (IPM) model is employed to deal with high-speed case. This new RFAT method can handle the maneuvering cases, high-speed cases, and bistatic radar cases, which are all possible in the missile-borne SAR. Besides, this raw signal simulation adopts the electromagnetic scattering calculation so that we do not need a scattering rate distribution map as the simulation input. Thus, the multiple electromagnetic reflections can be considered. Simulation examples prove the effectiveness of our method. Weijie Xia, Yuanyuan Qi, Linlin Huang, and Xue Jin Copyright © 2016 Weijie Xia et al. All rights reserved. A Circuit-Model-Navigated Design Process and Efficiency Estimation for Short-Circuited Self-Excited EBG Resonator Antenna Tue, 31 May 2016 09:26:59 +0000 http://www.hindawi.com/journals/ijap/2016/9327167/ The paper presents a circuit model for the computationally efficient design of a planar Short-Circuited Self-Excited EBG Resonator Antenna (SC SE-EBG-RA). To this purpose, the same circuit model previously presented for the Open-Circuited version of the antenna is modified to be applicable to the SC version. Detailed HFSS modeling and simulation corroborate the accuracy of the model in predicting the antenna resonance. The efficiency of the designed antenna is calculated by a simulated Wheeler Cap Method (WCM) and is compared with the standard efficiency given by the numerical analyzer. The EM modeling is arranged so as to incorporate the effects of the SMA connector, discontinuities, and the WC, emulating a real WC measurement and yielding a high degree of confidence in the results. Overall, a small antenna sized with 93% verified efficiency is achieved, which is also compiled with affordable manufacturing processes. Mehdi Hosseini Copyright © 2016 Mehdi Hosseini. All rights reserved. Cognitive MIMO Frequency Diverse Array Radar with High LPI Performance Tue, 31 May 2016 06:08:12 +0000 http://www.hindawi.com/journals/ijap/2016/2623617/ Frequency diverse array (FDA) has its unique advantage in realizing low probability of intercept (LPI) technology for its dependent beam pattern. In this paper, we proposed a cognitive radar based on the frequency diverse array multiple-input multiple-output (MIMO). To implement LPI of FDA MIMO transmit signals, a scheme for array weighting design is proposed, which is to minimize the energy of the target location and maximize the energy of the receiver. This is based on the range dependent characteristics of the frequency diverse array transmit beam pattern. To realize the objective problem, the algorithm is proposed as follows: the second-order nonconvex optimization problem is converted into a convex problem and solved by the bisection method and convex optimization. To get the information of target, the FDA MIMO radar is proposed to estimate the target parameters. Simulation results show that the proposed approach is effective in decreasing the detection probability of radar with lossless detection performance of the receive signal. Ling Huang, Kuandong Gao, Zhiming He, and Jingye Cai Copyright © 2016 Ling Huang et al. All rights reserved. Far-Field Testing Method of Spurious Emission Produced by HF RFID Mon, 30 May 2016 14:22:53 +0000 http://www.hindawi.com/journals/ijap/2016/4715898/ We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID) using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission is important from the security perspective as well as from the perspective of interference with other systems. Consequently we measured the harmonics produced in the integrated circuitry and characterized radiation properties of the antenna. Finally we present the measurements of the spurious emission performed in a Gigahertz Transverse Electromagnetic (GTEM) cell. Nikola Gvozdenovic, Ralph Prestros, and Christoph F. Mecklenbräuker Copyright © 2016 Nikola Gvozdenovic et al. All rights reserved. Dual-Resonant Implantable Circular Patch Antenna for Biotelemetry Communication Mon, 30 May 2016 09:45:59 +0000 http://www.hindawi.com/journals/ijap/2016/5262013/ A compact broadband implantable circular patch antenna is designed and experimentally demonstrated for Medical Implant Communications Service (MICS) band (402–405 MHz). Compared with other similar implantable antennas, the proposed antenna incorporates three advantages for biotelemetry communication. First, it can realize a broad impedance bandwidth by exhibiting dual resonances. Second, it can obtain a compact structure by introducing two arc-shaped slots, a rectangular slot and a circular slot on metal radiating patch. Finally, it can display a friendly shape by using a circular structure. The proposed antenna occupies a volume of about 431.5 mm3 (10.42 × 1.27 mm3), which is a compromise between miniaturization and bandwidth. The measured −10 dB impedance bandwidth is 55 MHz (385–440 MHz). Furthermore, the radiation performance and human body safety consideration of the antenna are examined and characterized. Rongqiang Li and Shaoqiu Xiao Copyright © 2016 Rongqiang Li and Shaoqiu Xiao. All rights reserved. A Novel Compact Dual-Polarized Antenna Thu, 26 May 2016 15:14:38 +0000 http://www.hindawi.com/journals/ijap/2016/6304356/ A novel compact dual-polarized antenna is proposed. The antenna has a 1.43% impedance bandwidth which is from 1801 MHz to 1827 MHz for return loss larger than 10 dB. The isolation between the two ports is above 28 dB in the bandwidth, and the gain is 6.6 dBi. The proposed antenna not only consists of a full-planar structure, but also is easy to be fabricated for its simple structure. Additionally, a section of slots and slits is cut on the radiation patch to reduce the area of it to 54% compared with the conventional square patch. Yong Cheng, Yadan Li, and Wenjun Lu Copyright © 2016 Yong Cheng et al. All rights reserved. A Dual-Band Printed End-Fire Antenna with DSPSL Feeding Thu, 26 May 2016 12:06:49 +0000 http://www.hindawi.com/journals/ijap/2016/9845392/ A novel dual-band printed end-fired antenna with double-sided parallel-strip line (DSPSL) feeding is presented. The DSPSL acts in wideband transition using balanced transmission. Two different modes of the parasitic patches allow the antenna to work in different bands. The printed antenna is designed as a quasi-Yagi structure to achieve directivity in the lower band, and the parallel rectangular patches serve as the parasitic director. These patches act as radiation patches with end-fire direction characteristics in the upper band. The measured bandwidths were 18.3% for the lower frequency band (2.28–2.74 GHz) and 12.6% for the upper frequency band (5.46–6.2 GHz). Daofeng Ye, Yuanxin Li, Zhixi Liang, and Yunliang Long Copyright © 2016 Daofeng Ye et al. All rights reserved. Improved OAM-Based Radar Targets Detection Using Uniform Concentric Circular Arrays Tue, 24 May 2016 07:11:56 +0000 http://www.hindawi.com/journals/ijap/2016/1852659/ Without any relative moves or beam scanning, the novel Orbital-Angular-Momentum- (OAM-) based radar targets detection technique using uniform concentric circular arrays (UCCAs) shows the azimuthal estimation ability, which provides new perspective for radar system design. However, the main estimation method, that is, Fast Fourier Transform (FFT), under this scheme suffers from low resolution. As a solution, this paper rebuilds the OAM-based radar targets detection model and introduces the multiple signal classification (MUSIC) algorithm to improve the resolution for detecting targets within the main lobes. The spatial smoothing technique is proposed to tackle the coherent problem brought by the proposed model. Analytical study and simulation demonstrate the superresolution estimation capacity the MUSIC algorithm can achieve for detecting targets within the main lobes. The performance of the MUSIC algorithm to detect targets not illuminated by the main lobes is further evaluated. Despite the fact that MUSIC algorithm loses the resolution advantage under this case, its estimation is more robust than that of the FFT method. Overall, the proposed MUSIC algorithm for the OAM-based radar system demonstrates the superresolution ability for detecting targets within the main lobes and good robustness for targets out of the main lobes. Mingtuan Lin, Yue Gao, Peiguo Liu, and Jibin Liu Copyright © 2016 Mingtuan Lin et al. All rights reserved. A Miniaturized Meandered Dipole UHF RFID Tag Antenna for Flexible Application Mon, 23 May 2016 11:38:35 +0000 http://www.hindawi.com/journals/ijap/2016/2951659/ A miniaturized meandered dipole antenna for UHF RFID tag is proposed. Different resonance frequencies and impedance can be achieved by adjusting the number of the meanders, which can help to reduce the size of the antenna. Due to the radiation patches, the input impedance of the antenna can be flexibly tuned in a large scale. The proposed antenna is printed on polyethylene (PET) substrate with a total volume of 48 mm × 13.7 mm × 0.5 mm. Modeling and simulation results show that the reflection coefficient of the antenna is less than −15 dB at 860–960 MHz. Experimental studies demonstrate that the minimum threshold power of the antenna is between 23 and 26 dBm and the measured read range is 3-4 m. Xiuwei Xuan, Lianrong Lv, and Kun Li Copyright © 2016 Xiuwei Xuan et al. All rights reserved. Ray-Based Statistical Propagation Modeling for Indoor Corridor Scenarios at 15 GHz Thu, 19 May 2016 12:03:30 +0000 http://www.hindawi.com/journals/ijap/2016/2523913/ According to the demands for fifth-generation (5G) communication systems, high frequency bands (above 6 GHz) need to be adopted to provide additional spectrum. This paper investigates the characteristics of indoor corridor channels at 15 GHz. Channel measurements with a vector network analyzer in two corridors were conducted. Based on a ray-optical approach, a deterministic channel model covering both antenna and propagation characteristic is presented. The channel model is evaluated by comparing simulated results of received power and root mean square delay spread with the corresponding measurements. By removing the impact of directional antennas from the transmitter and receiver, a path loss model as well as small-scale fading properties for typical corridors is presented based on the generated samples from the deterministic model. Results show that the standard deviation of path loss variation is related to the Tx height, and placing the Tx closer to the ceiling leads to a smaller fluctuation of path loss. Qi Wang, Bo Ai, Ke Guan, David W. Matolak, Ruisi He, and Xin Zhou Copyright © 2016 Qi Wang et al. All rights reserved. A Novel Adaptive Algorithm Addresses Potential Problems of Blind Algorithm Wed, 18 May 2016 14:25:32 +0000 http://www.hindawi.com/journals/ijap/2016/5983924/ A hybrid algorithm called constant modulus least mean square (CMLMS) algorithm is proposed in order to address the potential problems existing with constant modulus algorithm (CMA) about its convergence. It is a two-stage adaptive filtering algorithm and based on least mean square (LMS) algorithm followed by CMA. A hybrid algorithm is theoretically developed and the same is verified through MatLab Software. Theoretical model is verified through simulation and its performance is evaluated in smart antenna in presence of a cochannel interfering signal and additive white Gaussian noise (AWGN) of zero mean. This is also tested in Rayleigh fading channel using digital modulation technique for Bit Error Rate (BER). Finally, a few computer simulations are presented in order to substantiate the theoretical findings with respect to proposed model. Corresponding results obtained with the use of only CMA and LMS algorithms are also presented for further comparison. Muhammad Yasin and Muhammad Junaid Hussain Copyright © 2016 Muhammad Yasin and Muhammad Junaid Hussain. All rights reserved. Cavity-Backed Angled-Dipole Antennas for Millimeter-Wave Wireless Applications Tue, 17 May 2016 09:11:21 +0000 http://www.hindawi.com/journals/ijap/2016/5083807/ A cavity-backed angled-dipole antenna is proposed for millimeter-wave wireless applications. The angled-dipole radiator is built on both sides of an RT/Duroid 5880 substrate () and fed by a parallel-plate transmission line. The cavity-backed reflector is utilized to improve the radiation characteristics of the angled dipole, such as gain, back-radiation, symmetric pattern, and similar 3 dB beamwidth in the - and -planes. The design, with a cavity aperture of , results in a dB bandwidth of 26.7–30.6 GHz, a gain of 6.6–8.0 dB, and a similar 3 dB beamwidth of approximately 70° for both the - and -planes. Eight-element linear arrays with the proposed antenna having a center-to-center spacing of 5.6 mm are characterized, fabricated, and measured. By applying nonuniform power distribution across excitations, the array achieves a scan angle up to 40° and a sidelobe level below −15 dB. Son Xuat Ta and Ikmo Park Copyright © 2016 Son Xuat Ta and Ikmo Park. All rights reserved. Miniaturized Coupling Structures for Decoupling PIFAs on Handheld Devices Mon, 16 May 2016 11:16:19 +0000 http://www.hindawi.com/journals/ijap/2016/2854376/ One efficient approach is introduced in this paper to reduce mutual coupling and correlation coefficient for two closely placed PIFAs in a handheld device. The approach is based on one miniaturized structure which consists of two metallic layers, printed on either side of one thin dielectric layer. Due to the small spacing between two conducting patches, high electromagnetic field is induced within the dielectric layer. The geometry and position of this structure have been modified to decouple the PIFA array at 1.9 GHz and produce maximum miniaturization thereby occupying less space on a handheld device ground plane. By employing the proposed structures, a 20 dB reduction in mutual coupling is achieved. The correlation coefficient also reduces to 0.007278. The performance of the structure is validated by both simulated results and measured data obtained from several fabricated prototypes. Qian Li and Yaxin Yu Copyright © 2016 Qian Li and Yaxin Yu. All rights reserved. One-Step Leapfrog LOD-BOR-FDTD Algorithm with CPML Implementation Mon, 16 May 2016 10:44:46 +0000 http://www.hindawi.com/journals/ijap/2016/8402697/ An unconditionally stable one-step leapfrog locally one-dimensional finite-difference time-domain (LOD-FDTD) algorithm towards body of revolution (BOR) is presented. The equations of the proposed algorithm are obtained by the algebraic manipulation of those used in the conventional LOD-BOR-FDTD algorithm. The equations for -direction electric and magnetic fields in the proposed algorithm should be treated specially. The new algorithm obtains a higher computational efficiency while preserving the properties of the conventional LOD-BOR-FDTD algorithm. Moreover, the convolutional perfectly matched layer (CPML) is introduced into the one-step leapfrog LOD-BOR-FDTD algorithm. The equation of the one-step leapfrog CPML is concise. Numerical results show that its reflection error is small. It can be concluded that the similar CPML scheme can also be easily applied to the one-step leapfrog LOD-FDTD algorithm in the Cartesian coordinate system. Yi-Gang Wang, Yun Yi, Bin Chen, Hai-Lin Chen, Kang Luo, and Run Xiong Copyright © 2016 Yi-Gang Wang et al. All rights reserved. Pilot Design for Sparse Channel Estimation in Large-Scale MIMO-OFDM System Thu, 12 May 2016 14:59:49 +0000 http://www.hindawi.com/journals/ijap/2016/6142574/ The pilot design problem in large-scale multi-input-multioutput orthogonal frequency division multiplexing (MIMO-OFDM) system is investigated from the perspective of compressed sensing (CS). According to the CS theory, the success probability of estimation is dependent on the mutual coherence of the reconstruction matrix. Specifically, the smaller the mutual coherence is, the higher the success probability is. Based on this conclusion, this paper proposes a pilot design algorithm based on alternating projection and obtains a nonorthogonal pilot pattern. Simulation results show that applying the proposed pattern gives the better performance compared to applying conventional orthogonal one in terms of normalized mean square error (NMSE) of the channel estimate. Moreover, the bit error rate (BER) performance of the large-scale MIMO-OFDM system is improved. Chao Xu, Jianhua Zhang, Mengmeng Liu, and Changchuan Yin Copyright © 2016 Chao Xu et al. All rights reserved. Brush-Painting and Photonic Sintering of Copper Oxide and Silver Inks on Wood and Cardboard Substrates to Form Antennas for UHF RFID Tags Thu, 12 May 2016 14:54:38 +0000 http://www.hindawi.com/journals/ijap/2016/3694198/ Additive deposition of inks with metallic inclusions provides compelling means to embed electronics into versatile structures. The need to integrate electronics into environmentally friendly components and structures increases dramatically together with the increasing popularity of the Internet of Things. We demonstrate a novel brush-painting method for depositing copper oxide and silver inks directly on wood and cardboard substrates and discuss the optimization of the photonic sintering process parameters for both materials. The optimized parameters were utilized to manufacture passive ultra high frequency (UHF) radio frequency identification (RFID) tag antennas. The results from wireless testing show that the RFID tags based on the copper oxide and silver ink antennas on wood substrate are readable from ranges of 8.5 and 11 meters, respectively, and on cardboard substrate from read ranges of 8.5 and 12 meters, respectively. These results are well sufficient for many future wireless applications requiring remote identification with RFID. Erja Sipilä, Johanna Virkki, Jianhua Wang, Lauri Sydänheimo, and Leena Ukkonen Copyright © 2016 Erja Sipilä et al. All rights reserved. Cell Curvature and Far-Field Superconvergence in Numerical Solutions of Electromagnetic Integral Equations Thu, 12 May 2016 11:47:07 +0000 http://www.hindawi.com/journals/ijap/2016/9808637/ Two curved targets are used to explore far-field superconvergence effects arising in numerical solutions of the electric-field and magnetic-field integral equations. Three different orders of basis and testing functions are used to discretize these equations, and three different types of target models (flat facets, quadratic-curved facets, and cubic-curved facets) are employed. Ideal far-field convergence rates are only observed when the model curvature is one degree higher than the basis order. Andrew F. Peterson Copyright © 2016 Andrew F. Peterson. All rights reserved. Beam Performance Optimization of Multibeam Imaging Sonar Based on the Hybrid Algorithm of Binary Particle Swarm Optimization and Convex Optimization Thu, 12 May 2016 08:14:52 +0000 http://www.hindawi.com/journals/ijap/2016/3592973/ It should be noted that the peak sidelobe level (PSLL) significantly influences the performance of the multibeam imaging sonar. Although a great amount of work has been done to suppress the PSLL of the array, one can verify that these methods do not provide optimal results when applied to the case of multiple patterns. In order to suppress the PSLL for multibeam imaging sonar array, a hybrid algorithm of binary particle swarm optimization (BPSO) and convex optimization is proposed in this paper. In this algorithm, the PSLL of multiple patterns is taken as the optimization objective. BPSO is considered as a global optimization algorithm to determine best common elements’ positions and convex optimization is considered as a local optimization algorithm to optimize elements’ weights, which guarantees the complete match of the two factors. At last, simulations are carried out to illustrate the effectiveness of the proposed algorithm in this paper. Results show that, for a sparse semicircular array with multiple patterns, the hybrid algorithm can obtain a lower PSLL compared with existing methods and it consumes less calculation time in comparison with other hybrid algorithms. Weijie Xia, Xue Jin, and Fawang Dou Copyright © 2016 Weijie Xia et al. All rights reserved. Location Optimization for Square Array Antennas Using Differential Evolution Algorithm Tue, 10 May 2016 14:04:13 +0000 http://www.hindawi.com/journals/ijap/2016/1956047/ In recent works thinned arrays giving minimum peak sidelobe levels for planar square antenna arrays are obtained using Hadamard difference sets. In the current work thinned array configurations giving lower peak sidelobe levels than those given in the literature are obtained for square arrays of , , , and elements. Differential evolution algorithm is used in the determination of the antenna locations. Erkan Afacan Copyright © 2016 Erkan Afacan. All rights reserved. Implementation of Associated Hermite FDTD Method in Handling INBCs for Shielding Analysis Tue, 10 May 2016 13:39:10 +0000 http://www.hindawi.com/journals/ijap/2016/6893915/ For modeling of electrically thin conductive shields, the unconditionally stable Associated Hermite (AH) FDTD scheme is combined with the impedance network boundary conditions (INBCs) in this paper. The two-port network equations of INBCs in frequency domain are transformed into AH domain to represent the relationship of tangential components of the electric and magnetic fields at faces of the shield. The established AH-INBCs shielding boundaries are incorporated into a set of implicit equations to calculate the expansion coefficients vectors of electromagnetic fields in the computational domain. The method is free of CFL condition and no convolution integral operation for solving the conventional INBCs-FDTD is involved. Numerical example shows that, compared with analytical solutions and conventional FDTD method, the proposed algorithm is efficient and accurate. Lihua Shi, Zhengyu Huang, Qing Si, and Yinghui Zhou Copyright © 2016 Lihua Shi et al. All rights reserved. Design of Symmetrical Beam Triple-Aperture Waveguide Antenna for Primary Feed of Reflector Tue, 10 May 2016 12:57:05 +0000 http://www.hindawi.com/journals/ijap/2016/5830527/ This research presents a triple-aperture waveguide antenna as the primary feed of parabolic reflectors. The proposed antenna is able to rectify the asymmetry and also achieve a symmetrical unidirectional beam through the application of two parasitic coupling apertures. The design of the antenna is that of a rectangular waveguide (radiating aperture) vertically jointed to the two coupling apertures of the same measurement widthwise (i.e., one stacked on top and the other underneath) to achieve the symmetrical beam. The rectangular waveguide is 97.60 mm and 46.80 mm in width () and height (), respectively, to propagate the WLAN frequency band of 2.412–2.484 GHz. Simulations were carried out to determine the optimal antenna parameters and an antenna prototype was subsequently fabricated and tested. The simulated beamwidths in the - and -planes at  dB were equally 67° (i.e., 67° for both the - and -planes) and at  dB also equally 137°, while the measured results at  dB were equally 65° and at  dB equally 135°. The simulation and measured results are thus in good agreement. The simulated and measured antenna gains are, respectively, 8.25 dBi and 9.17 dBi. The findings validate the applicability of the antenna as the prime feed for rotationally symmetric parabolic reflectors. Kanawat Nuangwongsa and Chuwong Phongcharoenpanich Copyright © 2016 Kanawat Nuangwongsa and Chuwong Phongcharoenpanich. All rights reserved. Millimeter Wave Fabry-Perot Resonator Antenna Fed by CPW with High Gain and Broadband Tue, 10 May 2016 11:57:31 +0000 http://www.hindawi.com/journals/ijap/2016/3032684/ A novel millimeter wave coplanar waveguide (CPW) fed Fabry-Perot (F-P) antenna with high gain, broad bandwidth, and low profile is reported. The partially reflective surface (PRS) and the ground form the F-P resonator cavity, which is filled with the same dielectric substrate. A dual rhombic slot loop on the ground acts as the primary feeding antenna, which is fed by the CPW and has broad bandwidth. In order to improve the antenna gain, metal vias are inserted surrounding the F-P cavity. A CPW-to-microstrip transition is designed to measure the performances of the antenna and extend the applications. The measured impedance bandwidth of less than −10 dB is from 34 to 37.7 GHz (10.5%), and the gain is 15.4 dBi at the center frequency of 35 GHz with a 3 dB gain bandwidth of 7.1%. This performance of the antenna shows a tradeoff among gain, bandwidth, and profile. Xue-Xia Yang, Guan-Nan Tan, Bing Han, and Hai-Gao Xue Copyright © 2016 Xue-Xia Yang et al. All rights reserved. Design of an L-Band Cross-Dipole Phased Array Feed for FAST Mon, 09 May 2016 14:10:23 +0000 http://www.hindawi.com/journals/ijap/2016/5357368/ The Five-Hundred-Meter Aperture Spherical Telescope (FAST) is a Chinese megascience project that aims to build the largest single dish radio telescope in the world. Given its multiple simultaneous beam formation, phased array feed (PAF) is widely used to extend the field of view and enhance the survey speed of the radio telescope. In this study, a broadband and low cost PAF element using cross-dipole antenna at L-band is designed based on the requirement of the FAST. The antenna is fed by two microstrip baluns which have high performance and is easy to manufacture compared to the traditional coaxial balun. A simple system model is also introduced to evaluate the PAF performance. The measured results of the fabricated element and the simulations of the system performance validate the effectiveness of element design. Yubing Han and Luoqing Zhong Copyright © 2016 Yubing Han and Luoqing Zhong. All rights reserved. An Optimal Electric Dipole Antenna Model and Its Field Propagation Mon, 09 May 2016 13:47:22 +0000 http://www.hindawi.com/journals/ijap/2016/8601497/ An optimal electric dipole antennas model is presented and analyzed, based on the hemispherical grounding equivalent model and the superposition principle. The paper also presents a full-wave electromagnetic simulation for the electromagnetic field propagation in layered conducting medium, which is excited by the horizontal electric dipole antennas. Optimum frequency for field transmission in different depth is carried out and verified by the experimental results in comparison with previously reported simulation over a digital wireless Through-The-Earth communication system. The experimental results demonstrate that the dipole antenna grounding impedance and the output power can be efficiently reduced by using the optimal electric dipole antenna model and operating at the optimum frequency in a vertical transmission depth up to 300 m beneath the surface of the earth. Yidong Xu, Lili Guo, Wei Xue, Korochentsev Vladimir, and Junwei Qi Copyright © 2016 Yidong Xu et al. All rights reserved. A Small Planar Antenna for 4G Mobile Phone Application Mon, 09 May 2016 06:09:11 +0000 http://www.hindawi.com/journals/ijap/2016/4791831/ The analysis and design of a small planar multiband antenna operating in the 4G frequency bands are presented. The numerical and experimental results demonstrated that the proposed antenna satisfies the requirement of 6 dB return loss for the impedance bandwidth of the LTE700/LTE2300/LTE2500 and WiMAX3500 bands. The gains at 750 MHz/2.3 GHz/2.6 GHz/3.5 GHz are 2.1 dBi/4.9 dBi/4.7 dBi/4.3 dBi, respectively. The measured radiation patterns verify the suitability of the antenna to be employed in mobile phones. The dimensions of the radiant patch are 49 × 10 mm2. The proposed antenna can be easily fabricated and customized to various 4G mobile phones as a compact internal antenna. Hu Jian-rong, Li Jiu-sheng, and Wu Di Copyright © 2016 Hu Jian-rong et al. All rights reserved. Effect of Antenna Parameters on the Field Coverage in Tunnel Environments Thu, 05 May 2016 07:46:01 +0000 http://www.hindawi.com/journals/ijap/2016/8180124/ Radio wave propagation in confined spaces is consequent upon the reflections of boundaries; thus, the radiation characteristics of the antenna have significant influence on the field coverage in the confined space. This paper investigates the effects of antenna parameters on field coverage characteristics in a tunnel environment. A modified modal method is proposed to analyse the wave propagation properties along the tunnel. The relationships between the amplitudes of modes and the antenna parameters, including the beam width, beam direction, and antenna location, are analysed. The results indicate that by properly selecting the antenna parameters, optimum field coverage in tunnel environments can be realized. Dawei Li and Junhong Wang Copyright © 2016 Dawei Li and Junhong Wang. All rights reserved.