http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Wed, 22 May 2013 13:19:47 +0000 http://www.hindawi.com/journals/ijap/2013/516946/ The current focus in defense arena is towards the stealth technology with an emphasis to control the radar cross-section (RCS). The scattering from the antennas mounted over the platform is of prime importance especially for a low-observable aerospace vehicle. This paper presents the analysis of the scattering cross section of a uniformly spaced linear dipole array. Two types of feed networks, that is, series and parallel feed networks, are considered. The total RCS of phased array with either kind of feed network is obtained by following the signal as it enters through the aperture and travels through the feed network. The RCS estimation of array is done including the mutual coupling effect between the dipole elements in three configurations, that is, side-by-side, collinear, and parallel-in-echelon. The results presented can be useful while designing a phased array with optimum performance towards low observability. H. L. Sneha, Hema Singh, and R. M. Jha Copyright © 2013 H. L. Sneha et al. All rights reserved. Wed, 22 May 2013 10:23:50 +0000 http://www.hindawi.com/journals/ijap/2013/785675/ In order to better assess the behaviours of the propagation channel in a confined environment such as a railway tunnel for subway application, we present an optimization method for a deterministic channel simulator based on 3D ray tracing associated to the geometrical optics laws and the uniform theory of diffraction. This tool requires a detailed description of the environment. Thus, the complexity of this model is directly bound to the complexity of the environment and specifically to the number of facets that compose it. In this paper, we propose an algorithm to identify facets that have no significant impact on the wave propagation. This allows us to simplify the description of the geometry of the modelled environment by removing them and by this way, to reduce the complexity of our model and therefore its computation time. A comparative study between full and simplified environment is led and shows the impact of this proposed method on the characteristic parameters of the propagation channel. Thus computation time obtained from the simplified environment is 6 times lower than the one of the full model without significant degradation of simulation accuracy. Siham Hairoud, Pierre Combeau, Yannis Pousset, Yann Cocheril, Marion Berbineau, and Rodolphe Vauzelle Copyright © 2013 Siham Hairoud et al. All rights reserved. Mon, 20 May 2013 19:00:57 +0000 http://www.hindawi.com/journals/ijap/2013/649049/ Ultra wideband (UWB) systems are the most appropriate for high data rate wireless transmission with low power consumption. However, the antenna design for UWB has been a challenging task. Moreover, it is always desirable to have more freedom by designing different shape antennas with identical characteristics so that they can be used in either transmitter or receiver depending on other physical constraints such as area. To tackle these issues, in this paper, we have investigated a joint optimization of three different shape-printed monopole antennas, namely, printed square monopole antenna, printed circular monopole antenna and printed hexagonal monopole antenna, for UWB applications. More specifically, we have obtained the optimized geometrical parameters of these antennas by minimizing the mean-square-error for desired lower band edge frequency, quality factor, and bandwidth. The objective of joint optimization is to have identical frequency characteristics for the aforementioned three types of PMA which will give a freedom to interchangeably use them at either side, transmitting or receiving. Moreover, we employ particle swarm optimization (PSO) algorithm for our problem as it is well known in the literature that PSO performs well in electromagnetic and antenna applications. Simulation results are presented to show the performance of the proposed design. Muhammad Zubair and Muhammad Moinuddin Copyright © 2013 Muhammad Zubair and Muhammad Moinuddin. All rights reserved. Sun, 19 May 2013 13:29:30 +0000 http://www.hindawi.com/journals/ijap/2013/279070/ A new modeling method of cabin path loss prediction based on support vector machine (SVM) is proposed in this paper. The method is trained with the path loss values of measured points inside the cabin and can be used to predict the path loss values of the unmeasured points. The experimental results demonstrate that our modeling method is more accurate than the curve fitting method. This SVM-based path loss prediction method makes the prediction much easier and more accurate, which covers performance traditional methods in the channel propagation modeling. Xiaonan Zhao, Chunping Hou, and Qing Wang Copyright © 2013 Xiaonan Zhao et al. All rights reserved. Thu, 16 May 2013 14:42:02 +0000 http://www.hindawi.com/journals/ijap/2013/405943/ A novel reconfigurable compact patch array antenna for directional and broadside application is proposed. The presented antenna has successfully been able to function for directional beam at 320° or 35° and divisive broadside beam at 43° and 330°. This is realized in the unique form of aperture coupled spiral feeding technique and positioning of the radiating elements at 0°, 90,° and 180°. The switchable feature is effectively performed by the configuration of three PIN diodes. All PIN diodes are positioned at the specific location of the aperture coupled structure. It is discovered in simulation that the switches can be represented with a copper strip line or touchstone (TS) block . The proposed antenna design operates at 2.37 GHz to 2.41 GHz and has a maximum gain of 6.4 dB and efficiency of 85.97%. Such antenna produces a broadside HPBW with a wider bandwidth covering from −90° to 90° compared to the normal microstrip antenna which could only provide HPBW of −50° to 50°. Moreover, the proposed antenna has small physical dimension of 100 mm by 100 mm. The simulation and measurement results have successfully exhibited the idea of the presented antenna performance. Therefore, the antenna is sufficiently competent in the smart WiMAX antenna application. M. Jusoh, M. F. Jamlos, M. R. Kamarudin, and T. Sabapathy Copyright © 2013 M. Jusoh et al. All rights reserved. Thu, 16 May 2013 08:36:37 +0000 http://www.hindawi.com/journals/ijap/2013/649602/ A time domain channel prediction method exploiting features of sparse channel is proposed for orthogonal frequency division multiplexing (OFDM) systems. The proposed predictor operates in the time domain on each channel tap and separates the negligible taps from significant channel taps before performing prediction. We also compare the proposed prediction method with the classical frequency domain method realized at each OFDM subcarrier and demonstrate that our method increases the prediction accuracy and reduces the computational complexity. Simulations on the physical channel model verify the performance of the proposed method. Changwei Lv, Shujuan Hou, and Wenbo Mei Copyright © 2013 Changwei Lv et al. All rights reserved. Tue, 14 May 2013 14:29:44 +0000 http://www.hindawi.com/journals/ijap/2013/194145/ In many RFID practical applications, it is required that reader can effectively read tags which are placed in radiation covering area randomly. In this paper, a passive UHF dual-dipole tag antenna with quasi-isotropic patterns is designed, which can reduce the sensibility of tag read-orientation in a long distance. Two dipoles with four-axis reflection symmetric structure are used, and the two arms of the dipole are bent to fill the space of the antenna. In this way, a quasi-isotropic tag is easier to be obtained. The test results show that the gain deviation of the proposed antenna was less than 3.25 dB, and the maximum reading range in different directions was from 6.9 m to 10.0 m, with better quasi-isotropic performance and reading range than other commercial tags. Chunfang Qin, Lingfei Mo, Hongliang Zhou, and Hongjian Zhang Copyright © 2013 Chunfang Qin et al. All rights reserved. Mon, 13 May 2013 19:25:34 +0000 http://www.hindawi.com/journals/ijap/2013/738659/ This paper presents impact of layout sizes of Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT heterostructure high-mobility transistors (HEMTs) on SiC substrate on its characteristics that include the threshold voltage, the maximum transconductance, characteristic frequency, and the maximum oscillation frequency. The changing parameters include the gate finger number, the gate width per finger. The measurement results based on common-source devices demonstrate that the above parameters have different effects on the threshold voltage, maximum transconductance, and frequency characteristics. Liwei Jin, Zhiqun Cheng, and Qingna Wang Copyright © 2013 Liwei Jin et al. All rights reserved. Mon, 13 May 2013 18:15:56 +0000 http://www.hindawi.com/journals/ijap/2013/179296/ Passive radar (or Passive Coherent Localisation) is an advancing technology for covert operation. The signal transmitted from sources of opportunity such as radio or TV stations is used as illumination for a certain area of interest. Part of the transmitted signal is reflected by radar targets, for example, moving objects such as vehicles or aircraft. Typical radar parameters are derived from the comparison between the direct line-of-sight from the transmitter and the signal scattered from the target object. Such systems are an attractive addition to existing active radar stations because they have the potential to discover low-flying and low-observable targets and no active radar transmitter is required. Printed dipole antennas are very attractive antenna elements for such systems because of their easy fabrication, low-cost, polarisation purity, and low-profile properties. The present paper describes the design of an antenna array using printed dipole elements with flared arms for a passive radar system operating in the GSM900 frequency range. Isolated antenna elements and a small uniform linear antenna array were designed and optimised using computational electromagnetic methods. Several prototypes have been fabricated on conventional microwave PCB substrate material. Preliminary measurement results for antenna matching and far-field radiation patterns are shown. Peter Knott Copyright © 2013 Peter Knott. All rights reserved. Sun, 12 May 2013 07:58:54 +0000 http://www.hindawi.com/journals/ijap/2013/850489/ A compact handset multiple-input multiple-output (MIMO) antenna for long-term evolution (LTE) 700 band (746~787 MHz) applications is proposed. The proposed antenna consists of two symmetrical PIFAs. Without the usage of any additional coupling elements between closely mounted antennas, a high isolation (>15 dB) and a low enveloped correlation coefficient () are achieved by the optimum location and arrangement of MIMO antenna elements. Byeonggwi Mun, Frances J. Harackiewicz, Byeongkwan Kim, Hyunho Wi, Jonghyun Lee, Myun-Joo Park, Changwon Jung, and Byungje Lee Copyright © 2013 Byeonggwi Mun et al. All rights reserved. Thu, 09 May 2013 11:52:05 +0000 http://www.hindawi.com/journals/ijap/2013/417108/ This paper presents a kind of a multichannel THz detector using lens-based bow-tie array. A hyperhemispherical silicon lens is employed to provide a focal plane; 8 bow-tie elements are arranged on the focal plane with careful design to show a performance of broadband, high gain, well compact, and easy assembling. These characteristics of the detector are preferred for detecting weak THz signal. Measured far field shows that the radiation pattern of each element is shifted angularly, by ≈9°, which can be used for THz imaging. Tested responsivity of the detector shows a good spectral performance from 260 to 400 GHz: respective values were ≥220 V/W, and the best NEP is achieved at about 60 pW/. Besides that, the proposed antenna has advantages of simple structure, easy fabrication, and low cost. Hairui Liu, Junsheng Yu, Peter Huggard, and Byron Alderman Copyright © 2013 Hairui Liu et al. All rights reserved. Wed, 08 May 2013 18:45:56 +0000 http://www.hindawi.com/journals/ijap/2013/853594/ A miniaturized dual-mode bandpass filter (BPF) with elliptic function response using slot spurline is designed in this paper. The slot spurline can not only splits the degenerate modes but also determine the type of filter characteristic (Chebyshev or elliptic). To miniaturize the resonator, four sagittate stubs are proposed. For demonstration purpose, a BPF operating at 5.75 GHz for WLAN application was designed, fabricated, and measured. The measured results are in good agreement with the full-wave simulation results. Haiwen Liu, Jiuhuai Lei, Jing Wan, Yan Wang, Feng Yang, and Suping Peng Copyright © 2013 Haiwen Liu et al. All rights reserved. Wed, 08 May 2013 16:32:29 +0000 http://www.hindawi.com/journals/ijap/2013/410692/ Comparison of bioradiolocation and standard respiratory plethysmography signals during simultaneous registration of different types of the human breathing movements is performed in both time and frequency domains. For all couples of synchronized signals corresponding to bioradiolocation and respiratory plethysmography methods, the cross-correlation and spectral functions are calculated, and estimates of their generalized characteristics are defined. The obtained results consider bioradiolocation to be a reliable remote sensing technique for noncontact monitoring of breathing pattern in medical applications. Maksim Alekhin, Lesya Anishchenko, Alexander Tataraidze, Sergey Ivashov, Vladimir Parashin, and Alexander Dyachenko Copyright © 2013 Maksim Alekhin et al. All rights reserved. Tue, 07 May 2013 12:23:07 +0000 http://www.hindawi.com/journals/ijap/2013/847859/ This paper gives a feasible and simple solution of generating OAM-carrying radio beams. Eight Vivaldi antenna elements connect sequentially and fold into a hollow cylinder. The circular Vivaldi antenna array is fed with unit amplitude but with a successive phase difference from element to element. By changing the phase difference at the steps of 0, ±45°, ±90°, ±135°, and 180°, the OAM radio beam can be generated with mode numbers 0, ±1, ±2, ±3, and 4. Simulations show that the OAM states of ±2 and ±3 are the same as the traditional states, while the OAM states of 0, ±1, and 4 differ at the boresight. This phenomenon can be explained by the radiation pattern difference between Vivaldi antenna and tripole antenna. A solution of distinguishing OAM states is also proposed. The mode number of OAM can be distinguished with only 2 receivers. Changjiang Deng, Wenhua Chen, Zhijun Zhang, Yue Li, and Zhenghe Feng Copyright © 2013 Changjiang Deng et al. All rights reserved. Thu, 02 May 2013 10:55:53 +0000 http://www.hindawi.com/journals/ijap/2013/589591/ The capacity of Multiple Input Multiple Output (MIMO) system is highly related to the number of active antennas. But as the active antenna number increases, the MIMO system will consume more energy. To maximize the energy efficiency of MIMO system, we propose an antenna selection scheme which can maximize the energy efficiency of BS cluster. In the scheme, ergodic energy efficiency is derived according to large scale channel state information (CSI). Based on this ergodic energy efficiency, we introduce a cost function varied with the number of antennas, in which the effect to the energy efficiency of both the serving BS and the neighbor BS is considered. With this function, we can transform the whole system optimization problem to a sectional optimization problem and obtain a suboptimal antenna set using a heuristic algorithm. Simulation results verify that the proposed approach performs better than the comparison schemes in terms of network energy efficiency and achieves 98% network energy efficiency of the centralized antenna selection scheme. Besides, since the proposed scheme does not need the complete CSI of the neighbor BS, it can effectively reduce the signaling overhead. Yanjie Dong, Yinghai Zhang, Weidong Wang, Gaofeng Cui, and Yang Yu Copyright © 2013 Yanjie Dong et al. All rights reserved. Sat, 27 Apr 2013 15:48:14 +0000 http://www.hindawi.com/journals/ijap/2013/837639/ A modified space-time adaptive processing (STAP) estimator is described in this paper. The estimator combines the incremental multiparameter (IMP) algorithm and the existing beam-space preprocessing techniques yielding a computationally cheap algorithm for the superresolution of multiple signals. It is a potential technique for the remote sensing of the ocean currents from the broadened first-order Bragg sea echo spectrum of shipborne high-frequency surface wave radar (HFSWR). Some simulation results and real-data analysis are shown to validate the proposed algorithm. Zhongbao Wang, Junhao Xie, Zilong Ma, and Taifan Quan Copyright © 2013 Zhongbao Wang et al. All rights reserved. Wed, 24 Apr 2013 14:22:39 +0000 http://www.hindawi.com/journals/ijap/2013/819695/ Medical implants based on wireless communication will play crucial role in healthcare systems. Some applications need to know the exact position of each implant. RF positioning seems to be an effective approach for implant localization. The two most common positioning data typically used for RF positioning are received signal strength and time of flight of a radio signal between transmitter and receivers (medical implant and network of reference devices with known position). This leads to positioning methods: received signal strength (RSS) and time of arrival (ToA). Both methods are based on trilateration. Used positioning data are very important, but the positioning algorithm which estimates the implant position is important as well. In this paper, the proposal of novel algorithm for trilateration is presented. The proposed algorithm improves the quality of basic trilateration algorithms with the same quality of measured positioning data. It is called Enhanced Positioning Trilateration Algorithm (EPTA). The proposed algorithm can be divided into two phases. The first phase is focused on the selection of the most suitable sensors for position estimation. The goal of the second one lies in the positioning accuracy improving by adaptive algorithm. Finally, we provide performance analysis of the proposed algorithm by computer simulations. Peter Brida and Juraj Machaj Copyright © 2013 Peter Brida and Juraj Machaj. All rights reserved. Wed, 24 Apr 2013 14:04:29 +0000 http://www.hindawi.com/journals/ijap/2013/282373/ With the trend of the miniaturization, broadband, and integration of multisystems of wireless communication terminals, a new ultrawideband planar inverted-F antenna (PIFA) with capacitive ground plane is proposed in this paper. The capacitive ground plane is composed of a sheet of metal islands, which makes a major contribution to ultra-wideband from 2.3 GHz to 9.0 GHz by applying the capacitive compensation for input impedance of the PIFA in high-order modes frequency bands. The effect of geometric parameters of capacitive ground plane and antenna height on antenna performance is analyzed. It is found that the radiation pattern in free space and the gain of the proposed antenna also meet the demands of the wireless communication terminals. The reported antenna was fabricated and measured, and the experimental results are in good agreement with the simulation results. Haixia Liu, Fei Wang, Yang Yang, Xiaowei Shi, and Long Li Copyright © 2013 Haixia Liu et al. All rights reserved. Tue, 23 Apr 2013 15:55:53 +0000 http://www.hindawi.com/journals/ijap/2013/941924/ An overview on compact Planar Inverted-F Antennas (PIFAs) that are suitable for monitor-equipped devices is presented. In particular, high efficiency PIFAs (without any dielectric layer) with a percentage bandwidth (%BW) greater than 59% (470–862 MHz DVB-T band) are considered. In this context, two PIFA configurations are reviewed, where a dual-band feature has been obtained, in the 3300–3800 MHz (14% percentage bandwidth) WiMAX and 2400–2484 MHz (2.7% percentage bandwidth) WLAN IEEE 802.11b,g frequency bands, respectively, to also guarantee web access to on-demand services. The two PIFAs fill an overall volume of  mm3 and  mm3, respectively. They are composed of a series of branches, properly dimensioned and separated to generate the required resonances. Finally, to show the extreme flexibility of the previous two configurations, a novel dual-band L-shape PIFA has been designed. A reflection coefficient less than −6 dB and −10 dB and an antenna gain of around 2 dBi and 6.3 dBi have been obtained in the 470–862 MHz DVB-T band and the 2400–2484 MHz WLAN band, respectively. The L-shape PIFA prototype can be obtained by properly cutting and folding a single metal sheet, thus resulting in a relatively low-cost and mechanically robust antenna configuration. Andrea D'alessandro, Roberto Caso, Marcos R. Pino, and Paolo Nepa Copyright © 2013 Andrea D'alessandro et al. All rights reserved. Tue, 23 Apr 2013 15:09:11 +0000 http://www.hindawi.com/journals/ijap/2013/823626/ A plasma sheath enveloping a reentry vehicle would affect performances of on-board antenna greatly, especially the navigation antennas. This paper studies the effects of reentry plasma sheath on a GPS right-hand circularly polarized (RHCP) patch antenna polarization property during a typical reentry process. Utilizing the algorithm of finite integration technique, the polarization characteristic of a GPS antenna coated by a plasma sheath is obtained. Results show that the GPS RHCP patch antenna radiation pattern distortions as well as polarization deteriorations exist during the entire reentry process, and the worst polarization mismatch loss between a GPS antenna and RHCP GPS signal is nearly 3 dB. This paper also indicates that measures should be taken to alleviate the plasma sheath for maintaining the GPS communication during the reentry process. L. Zhao, B. W. Bai, W. M. Bao, and X. P. Li Copyright © 2013 L. Zhao et al. All rights reserved. Mon, 22 Apr 2013 16:43:50 +0000 http://www.hindawi.com/journals/ijap/2013/167368/ With picocells deployed in the coverage of a macrocell in heterogeneous networks (HetNets), the macrocell evolved NodeB (MeNB) may receive interference signals from the picocell users, which results in more severe co-channel interference (CCI) problem in the uplink. In this paper, the spatial uplink interference coordination is investigated in multiple antenna systems, according to which the receiver coding matrix is generated by MeNB to mitigate the CCI from picocell users. Two interference coordination (IC) schemes are proposed based on whether the receiver coding matrix is full rank or not, named as full coding (IC-FC) and part coding (IC-PC), respectively. The application of the proposed schemes is discussed in single picocell and multiple picocell scenarios. The CCI can be totally canceled in single picocell scenario, and an algorithm is developed in multiple picocell networks to mitigate the most severely interfering picocell. Link level and system level simulations are applied, and it is shown that significant performance gain is achieved by our proposed schemes over traditional IC receivers. Yuan Li, Li Zhang, Hua Chen, and Mugen Peng Copyright © 2013 Yuan Li et al. All rights reserved. Mon, 22 Apr 2013 16:25:15 +0000 http://www.hindawi.com/journals/ijap/2013/348123/ The mutual coupling between antenna elements affects the antenna parameters like terminal impedances, reflection coefficients and hence the antenna array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar cross section (RCS). This coupling effect is also known to directly or indirectly influence the steady state and transient response, the resolution capability, interference rejection, and direction-of-arrival (DOA) estimation competence of the array. Researchers have proposed several techniques and designs for optimal performance of phased array in a given signal environment, counteracting the coupling effect. This paper presents a comprehensive review of the methods that model and mitigate the mutual coupling effect for different types of arrays. The parameters that get affected due to the presence of coupling thereby degrading the array performance are discussed. The techniques for optimization of the antenna characteristics in the presence of coupling are also included. Hema Singh, H. L. Sneha, and R. M. Jha Copyright © 2013 Hema Singh et al. All rights reserved. Mon, 22 Apr 2013 13:51:08 +0000 http://www.hindawi.com/journals/ijap/2013/396459/ An electromagnetic sensing system for the measurement of the respiratory activity is presented. The aims are to demonstrate the feasibility of the proposed approach and in particular to evaluate the effect on the measured signal of the distance between the subject and the sensing apparatus. Moreover, an electromagnetic model of the system, including the monitored subject, is proposed as a tool to solve the problem of selecting working parameters for system design. The sensing system is based on the measurement of the phase variation of the reflection coefficient caused by the respiratory activity. The phase signal compared with the thorax displacement measured by a reference instrument shows a high correlation () for different subject postures (sitting, standing, and lying) and a reduction of the signal amplitude with the distance  dB/cm is reported. The numerical simulations performed on a wide-band highlight the frequencies where the method exhibits the highest sensitivity to thorax movements. The sensitivity can be further improved by reducing the antenna beamwidth. Despite the signal amplitude reduction, the proposed system makes it possible to correctly operate at distances up to 2.5 m. Lorenzo Scalise, Valter Mariani Primiani, Paola Russo, Alfredo De Leo, Desar Shahu, and Graziano Cerri Copyright © 2013 Lorenzo Scalise et al. All rights reserved. Mon, 22 Apr 2013 11:26:01 +0000 http://www.hindawi.com/journals/ijap/2013/976301/ We propose a novel precoding algorithm that is a zero-forcing (ZF) method combined with adaptive beamforming in the Worldwide Interoperability for Microwave Access (WiMAX) system. In a Multiuser Multiple-Input Multiple-Output (MU-MIMO) system, ZF is used to eliminate the Multiple Access Interference (MAI) in order to allow several users to share a common resource. The adaptive beamforming algorithm is used to achieve the desired SNR gain. The experimental system consists of a WiMAX base station that has 2 MIMO elements, each of which is composed of three-array antennas and two mobile terminals, each of which has a single antenna. Through computer simulations, we verified that the proposed method outperforms the conventional ZF method by at least 2.4 dB when the BER is 0.1%, or 1.7 dB when the FER is 1%, in terms of the SNR. Through a hardware implementation of the proposed method, we verified the feasibility of the proposed method for realizing a practical WiMAX base station to utilize the channel resources as efficiently as possible. Hyunwook Yang and Seungwon Choi Copyright © 2013 Hyunwook Yang and Seungwon Choi. All rights reserved. Sun, 21 Apr 2013 11:31:37 +0000 http://www.hindawi.com/journals/ijap/2013/572923/ The information about the distance of separation between two-point targets that is contained in scattering data is explored in the context of the scalar Helmholtz operator via the Fisher information and associated Cramér-Rao bound (CRB) relevant to unbiased target separation estimation. The CRB results are obtained for the exact multiple scattering model and, for reference, also for the single scattering or Born approximation model applicable to weak scatterers. The effects of the sensing configuration and the scattering parameters in target separation estimation are analyzed. Conditions under which the targets' separation cannot be estimated are discussed for both models. Conditions for multiple scattering to be useful or detrimental to target separation estimation are discussed and illustrated. Edwin A. Marengo and Paul Berestesky Copyright © 2013 Edwin A. Marengo and Paul Berestesky. All rights reserved. Sun, 21 Apr 2013 11:18:14 +0000 http://www.hindawi.com/journals/ijap/2013/781357/ A novel miniaturized circularly polarized (CP) microstrip antenna that can handle UHF band (920–925 MHz, corresponding to the assigned band for RFID in China) has been designed, fabricated, and measured in this paper. The miniaturization of antenna is achieved by a special cross-shaped fractal metamaterial structure that is inserted between the patch and ground plane. The measured results show that the antenna possesses an impedance bandwidth of 8.7% with VSWR 1.5 : 1 and 3-dB axial bandwidth of 3.8%. Furthermore, the proposed antenna has 10.2% size reduction compared with traditional patch antenna. The tested results are in good agreement with that of the simulations. Guo Liu, Liang Xu, and Zhensen Wu Copyright © 2013 Guo Liu et al. All rights reserved. Sun, 21 Apr 2013 10:28:32 +0000 http://www.hindawi.com/journals/ijap/2013/507158/ Electromagnetic band gap (EBG) technology has become a significant breakthrough in the radio frequency (RF) and microwave applications due to their unique band gap characteristics at certain frequency ranges. Since 1999, the EBG structures have been investigated for improving performances of numerous RF and microwave devices utilizing the surface wave suppression and the artificial magnetic conductor (AMC) properties of these special type metamaterial. Issues such as compactness, wide bandwidth with low attenuation level, tunability, and suitability with planar circuitry all play an important role in the design of EBG structures. Remarkable efforts have been undertaken for the development of EBG structures to be compatible with a wide range of wireless communication systems. This paper provides a comprehensive review on various EBG structures such as three-, two-, and one-dimensional (3D, 2D, and 1D) EBG, mushroom and uniplanar EBG, and their successive advancement. Considering the related fabrication complexities, implementation of vialess EBG is an attractive topic for microwave engineers. For microstrip antennas, EBG structures are used in diversified ways, which of course found to be effective except in some cases. The EBG structures are also successfully utilized in antenna arrays for reducing the mutual coupling between elements of the array. Current challenges and limitations of the typical microstrip antennas and different EBG structures are discussed in details with some possible suggestions. Hopefully, this survey will guide to increasing efforts towards the development of more compact, wideband, and high-efficient uniplanar EBG structures for performance enhancement of antenna and other microwave devices. Md. Shahidul Alam, Norbahiah Misran, Baharudin Yatim, and Mohammad Tariqul Islam Copyright © 2013 Md. Shahidul Alam et al. All rights reserved. Sun, 21 Apr 2013 09:18:50 +0000 http://www.hindawi.com/journals/ijap/2013/181579/ With the development of mobile internet service, long-term evolution (LTE) system was proposed in the third generation partnership project (3GPP) to provide higher data rates and frequency efficiency. Since the year of 2010, 113 LTE networks have been commercially deployed worldwide, and most of the networks are based on frequency division duplexing (FDD). In this paper, measurement methods of four MIMO transmission modes (TMs) in time division-LTE (TD-LTE) are studied and analyzed. Link level simulation is carried out to evaluate the downlink throughput for different signal-to-noise ratios and parameter settings. Furthermore, indoor and field tests are also presented in the paper to investigate how real-world propagation affects the capacity and the error performance of MIMO transmission scheme. For the indoor test, radio channel emulators are applied to generate realistic wireless fading channel, while in the field trials, a live TD-LTE experiment cellular network is built, which contains several evolved nodeBs (eNBs) and a precommercial user equipment (UE). It is shown from both simulation and tests results that MIMO deployment gives a substantial performance improvement compared with the third generation wireless networks. Xiang Zhang, Xinyu Gu, Wenyu Li, Lin Zhang, Jia Shen, and Yi Wan Copyright © 2013 Xiang Zhang et al. All rights reserved. Thu, 18 Apr 2013 16:50:10 +0000 http://www.hindawi.com/journals/ijap/2013/607430/ An evolutionary programming approach, the so-called structure based evolutionary design, is applied to the synthesis of planar periodic electronic band gap in order to obtain an artificial magnetic conductor surface. We show that this strategy, in conjunction with a flexible aperture-oriented approach, allows for obtaining new and effective structures. This almost unique ability is exploited to obtain an artificial magnetic conductor periodic surface with a bandwidth larger than the most popular surfaces known so far. Luisa Deias, Giuseppe Mazzarella, Giorgio Montisci, and Giovanni Andrea Casula Copyright © 2013 Luisa Deias et al. All rights reserved. Thu, 18 Apr 2013 10:14:51 +0000 http://www.hindawi.com/journals/ijap/2013/509878/ Blind spots (or bad sampling points) in indoor areas are the positions where no signal exists (or the signal is too weak) and the existence of a receiver within the blind spot decelerates the performance of the communication system. Therefore, it is one of the fundamental requirements to eliminate the blind spots from the indoor area and obtain the maximum coverage while designing the wireless networks. In this regard, this paper combines ray-tracing (RT), genetic algorithm (GA), depth first search (DFS), and branch-and-bound method as a new technique that guarantees the removal of blind spots and subsequently determines the optimal wireless coverage using minimum number of transmitters. The proposed system outperforms the existing techniques in terms of algorithmic complexity and demonstrates that the computation time can be reduced as high as 99% and 75%, respectively, as compared to existing algorithms. Moreover, in terms of experimental analysis, the coverage prediction successfully reaches 99% and, thus, the proposed coverage model effectively guarantees the removal of blind spots. A. W. Reza, K. Dimyati, K. A. Noordin, M. J. Islam, M. S. Sarker, and H. Ramiah Copyright © 2013 A. W. Reza et al. All rights reserved.