International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Pilot Contamination Mitigation via a Novel Time-Shift Pilot Scheme in Large-Scale Multicell Multiuser MIMO Systems Thu, 01 Dec 2016 12:04:47 +0000 http://www.hindawi.com/journals/ijap/2016/7628692/ We propose a novel time-shift pilot scheme to mitigate the pilot contamination in large-scale multicell multiuser MIMO (LS-MIMO) systems. In the proposed scheme, the length of the uplink training pilot sequence is equal to the cell number; that is to say, the same pilot sequence is used within a cell, while for different cells, pilot sequences are mutually orthogonal. Moreover, users within a cell transmit the same pilot sequence in a time-shift manner during the channel estimation stage and in this way all user terminals’ channel state information can be estimated without contamination. The asymptotic channel orthogonality is studied in the LS-MIMO system, with which the mutual interference among cells caused by data and pilot sequences can be cancelled with the successive interference cancellation (SIC) method. We explore the superiority of the proposed scheme in channel coefficient estimation, uplink data detection, and downlink data transmission steps. Theoretical analysis and simulation results demonstrate that the proposed time-shift pilot design can alleviate the pilot contamination problem and improve the performance of the considered system significantly compared with the popular orthogonal pilots. Zhangkai Luo, Huali Wang, and Wanghan Lv Copyright © 2016 Zhangkai Luo et al. All rights reserved. A New Efficient Algorithm for the 2D WLP-FDTD Method Based on Domain Decomposition Technique Wed, 30 Nov 2016 13:13:31 +0000 http://www.hindawi.com/journals/ijap/2016/3163781/ This letter introduces a new efficient algorithm for the two-dimensional weighted Laguerre polynomials finite difference time-domain (WLP-FDTD) method based on domain decomposition scheme. By using the domain decomposition finite difference technique, the whole computational domain is decomposed into several subdomains. The conventional WLP-FDTD and the efficient WLP-FDTD methods are, respectively, used to eliminate the splitting error and speed up the calculation in different subdomains. A joint calculation scheme is presented to reduce the amount of calculation. Through our work, the iteration is not essential to obtain the accurate results. Numerical example indicates that the efficiency and accuracy are improved compared with the efficient WLP-FDTD method. Bo-Ao Xu, Yan-Tao Duan, Bin Chen, Yun Yi, and Kang Luo Copyright © 2016 Bo-Ao Xu et al. All rights reserved. Efficient AM Algorithms for Stochastic ML Estimation of DOA Mon, 28 Nov 2016 11:29:13 +0000 http://www.hindawi.com/journals/ijap/2016/4926496/ The estimation of direction-of-arrival (DOA) of signals is a basic and important problem in sensor array signal processing. To solve this problem, many algorithms have been proposed, among which the Stochastic Maximum Likelihood (SML) is one of the most concerned algorithms because of its high accuracy of DOA. However, the estimation of SML generally involves the multidimensional nonlinear optimization problem. As a result, its computational complexity is rather high. This paper addresses the issue of reducing computational complexity of SML estimation of DOA based on the Alternating Minimization (AM) algorithm. We have the following two contributions. First using transformation of matrix and properties of spatial projection, we propose an efficient AM (EAM) algorithm by dividing the SML criterion into two components. One depends on a single variable parameter while the other does not. Second when the array is a uniform linear array, we get the irreducible form of the EAM criterion (IAM) using polynomial forms. Simulation results show that both EAM and IAM can reduce the computational complexity of SML estimation greatly, while IAM is the best. Another advantage of IAM is that this algorithm can avoid the numerical instability problem which may happen in AM and EAM algorithms when more than one parameter converges to an identical value. Haihua Chen, Shibao Li, Jianhang Liu, Yiqing Zhou, and Masakiyo Suzuki Copyright © 2016 Haihua Chen et al. All rights reserved. 2D Efficient Unconditionally Stable Meshless FDTD Algorithm Sun, 27 Nov 2016 14:03:35 +0000 http://www.hindawi.com/journals/ijap/2016/8749071/ This paper presents an efficient weighted Laguerre polynomials based meshless finite-difference time domain (WLP-MFDTD). By decomposing the coefficients of the system matrix and adding a perturbation term, a factorization-splitting scheme is introduced. The huge sparse matrix is transformed into two matrices with 9 unknown elements in each row regardless of the duplicated ones. Consequently, compared with the conventional implementation, the CPU time and memory requirement can be saved greatly. The perfectly matched layer absorbing boundary condition is also extended to this approach. A numerical example demonstrates the capability and efficiency of the proposed method. Kang Luo, Yun Yi, Yantao Duan, Boao Xu, and Bin Chen Copyright © 2016 Kang Luo et al. All rights reserved. Scalable Notch Antenna System for Multiport Applications Sun, 27 Nov 2016 11:12:58 +0000 http://www.hindawi.com/journals/ijap/2016/7038103/ A novel and compact scalable antenna system is designed for multiport applications. The basic design is built on a square patch with an electrical size of (at 2.4 GHz) on a dielectric substrate. The design consists of four symmetrical and orthogonal triangular notches with circular feeding slots at the corners of the common patch. The 4-port antenna can be simply rearranged to 8-port and 12-port systems. The operating band of the system can be tuned by scaling () the size of the system while fixing the thickness of the substrate. The antenna system with : 1/1 in size of  mm2 operates at the frequency band of 2.3–3.0 GHz. By scaling the antenna with : 1/2.3, a system of  mm2 is achieved, and thus the operating band is tuned to 4.7–6.1 GHz with the same scattering characteristic. A parametric study is also conducted to investigate the effects of changing the notch dimensions. The performance of the antenna is verified in terms of the antenna characteristics as well as diversity and multiplexing parameters. The antenna system can be tuned by scaling so that it is applicable to the multiport WLAN, WIMAX, and LTE devices with port upgradability. Abdurrahim Toktas Copyright © 2016 Abdurrahim Toktas. All rights reserved. Design and Development of a New Electrically Small 3D UHF Spherical Antenna with 360° of Opening Angle in the Whole Space for RFID, WSN, and RSN Applications Wed, 23 Nov 2016 13:58:29 +0000 http://www.hindawi.com/journals/ijap/2016/2906149/ Several antenna designs have been made in order to obtain a novel electrically small 3D UHF spherical antenna (ka = 0.1916), which has a resonance frequency close to 915 MHz, produces a quasi-isotropic radiation with an opening angle equal to 360° in the whole space, and is used for RFID, WSN, and RSN applications. These antennas are based on different shapes and are wrapped on the Styrofoam sphere surface of dielectric constant close to air (). A T-match configuration is used to adapt the input impedance of antennas to a value of 50 Ω. The antennas form allows for placing the sensor electronics in its interior, to reconfigure it for numerous values of impedances and to operate it in other ISM bands by adjusting their geometric parameters. Abdelhamid Bou-El-Harmel, Ali Benbassou, and Jamal Belkadid Copyright © 2016 Abdelhamid Bou-El-Harmel et al. All rights reserved. Analysis of Spatial Diversity in Both Transmitter and Receiver on Low-Height Links at Forests Wed, 23 Nov 2016 07:21:24 +0000 http://www.hindawi.com/journals/ijap/2016/9682627/ This work focuses on radio wave propagation within forested environments, at 5.8 GHz. Concretely, we explore the advantages of implementing spatial diversity in reception or even in both ends for improving the strength of the received signal in such environments, which could be useful in applications such as vehicle-to-infrastructure, vehicle-to-vehicle, or emergency communications. Measurements gathered at both evergreen and deciduous forests sustain the thesis. Once processed, the results support the proposal of implementing a spatial diversity technique in reception or in both ends using a 2 × 4 (or 2 × 2) scheme in order to improve the connectivity at 5.8 GHz band within forests. In fact, we estimated a gain due to spatial diversity in reception of 5 dB and 2 dB at evergreen and deciduous forests, respectively, and 16 dB or 5 dB when implementing at both ends. Iñigo Cuiñas, Paula Gómez-Pérez, José A. Gay-Fernández, Javier López, Diego Pascual, Laura Rodríguez, and Marta Muñiz Copyright © 2016 Iñigo Cuiñas et al. All rights reserved. A Dual-Band Multiple Input Multiple Output Frequency Agile Antenna for GPSL1/Wi-Fi/WLAN2400/LTE Applications Tue, 22 Nov 2016 14:27:00 +0000 http://www.hindawi.com/journals/ijap/2016/9419183/ A novel dual-band, single element multiple input multiple output (MIMO) dielectric resonator antenna (DRA) with a modest frequency tuning ability is presented in this communication. The proposed antenna operates at GPS L1/Bluetooth/Wi-Fi/LTE2500/WLAN2400 frequency bands. A single dielectric resonator element is fed by two coaxial probes to excite the orthogonal modes. A couple of slots are introduced on the ground plane to improve the isolation between antenna ports. The slots also serve the purpose of reconfiguration in the lower band on placement of switches at optimized locations. The measured impedance bandwidth is 5.16% (1.41–1.49 GHz) in the lower band and 26% (2.2–2.85 GHz) in the higher band. The lower band reconfigures with an impedance bandwidth of 6.5% (1.55–1.65 GHz) when PIN diodes are switched ON. The gain, efficiency, correlation coefficient, and diversity gain of the MIMO DRA are presented with a close agreement between simulated and measured results. Sajid Aqeel, M. H. Jamaluddin, Aftab Ahmad Khan, Rizwan Khan, M. R. Kamarudin, Jalil-ur-Rehman Kazim, and Owais Owais Copyright © 2016 Sajid Aqeel et al. All rights reserved. Ultrasmall Dual-Band Metamaterial Antennas Based on Asymmetrical Hybrid Resonators Sun, 20 Nov 2016 07:57:01 +0000 http://www.hindawi.com/journals/ijap/2016/7019268/ A new type of hybrid resonant circuit model is investigated theoretically and experimentally. The resonant model consists of a right hand (RH) patch part and a composite right and left handed (CRLH) part (RH + CRLH), which determines a compact size and also a convenient frequency modulation characteristic for the proposed antennas. For experimental demonstration, two antennas are fabricated. The former dual-band antenna operating at  GHz (Wimax) and  GHz (WLAN) occupies an area of , and two dipolar radiation patterns are obtained with comparable gains of about 6.1 and 6.2 dB, respectively. The latter antenna advances in many aspects such as an ultrasmall size of only , versatile radiation patterns with a monopolar pattern at  GHz (Bluetooth), and a dipole one at  GHz (Wimax) and also comparable antenna gains. Circuit parameters are extracted and researched. Excellent performances of the antennas based on hybrid resonators predict promising applications in multifunction wireless communication systems. Ji-Xu Zhu, Peng Bai, and Jia-Fu Wang Copyright © 2016 Ji-Xu Zhu et al. All rights reserved. Online Calibration for LTE-Based Antenna Array System Sun, 20 Nov 2016 07:56:13 +0000 http://www.hindawi.com/journals/ijap/2016/2645870/ This paper presents a novel calibration method that equalizes the impulse responses of all the Radio Frequency (RF) modules of an antenna array system operating in Long-Term Evolution (LTE) evolved NodeB (eNB). The proposed technique utilizes the Zadoff-Chu (Z-C) sequence of the Primary Synchronization Signal (PSS) and Sounding Reference Signal (SRS) that are available in every LTE data frame for downlink and uplink, respectively, for estimating and compensating the differences in the impulse responses among the RF modules. The proposed calibration method is suitable for wide bandwidth signal environments of LTE because it equalizes the impulse response of each RF module, which is ultimately equivalent to compensate the phase and amplitude differences among RF modules for the entire frequency band. In addition, the proposed method is applicable while the target eNB is transmitting or receiving a data stream. From various experimental tests obtained from a test-bed implemented with 2 RF modules, it has been verified that the proposed method provides a reliable calibration for Release 10 Time Division Duplex (TDD) LTE signals. Phase errors after the calibration in our test-bed have been found to be about 2.418° and 2.983° for downlink and uplink, respectively. Kyunghoon Kim, Hyunwook Yang, Jaehyun Jang, Tiefeng Sun, Seungwon Choi, and Jaeho Jung Copyright © 2016 Kyunghoon Kim et al. All rights reserved. A Tuning Computation Technique for a Multiple-Antenna-Port and Multiple-User-Port Antenna Tuner Sun, 20 Nov 2016 07:19:45 +0000 http://www.hindawi.com/journals/ijap/2016/4758486/ A multiple-user-port antenna tuner having the structure of a multidimensional -network has recently been disclosed, together with design equations which assume lossless circuit elements. This paper is about the design of this type of antenna tuner, when losses are taken into account in each circuit element of the antenna tuner. The problem to be solved is the tuning computation, the intended results of which are the reactance values of the adjustable impedance devices of the antenna tuner, which provide an ideal match, if such reactance values exist. An efficient iterative tuning computation technique is presented and demonstrated. Frédéric Broydé and Evelyne Clavelier Copyright © 2016 Frédéric Broydé and Evelyne Clavelier. All rights reserved. The Effect of Refractivity on Propagation at UHF and VHF Frequencies Thu, 17 Nov 2016 13:47:48 +0000 http://www.hindawi.com/journals/ijap/2016/4138329/ This paper is using weather parameters to investigate the effect of refractivity on propagation in the first kilometer of the atmosphere over the English Channel for a long transhorizon path of 140 km. Different refractivity profiles are constructed based on meteorological data taken from the UK Meteorological Office in order to investigate the effects of refractivity on propagation. The analysis is made for the hourly experimental path loss between the transmitter and receiver obtained from the experimental setup comprised of two communication links. The frequency of operation of the first link is 2015 MHz and that of the second link is 240 MHz. Parabolic equation method is modelled to get an hourly modelled path loss corresponding to each hourly experimental path loss to be analyzed for the said communication links. The correlation between the modelled path loss and experimental path loss is computed for refractivity distribution recommended by the ITU and predicted profiles. It is inferred from the simulated and experimental results that little or no influence exists by the evaporation duct upon path loss at 2015 MHz specifically for a long path of 140 km over the sea. I. Alam, N. Mufti, S. A. A. Shah, and M. Yaqoob Copyright © 2016 I. Alam et al. All rights reserved. Propagation Characteristics of Oblique Incident Terahertz Wave in Nonuniform Dusty Plasma Thu, 17 Nov 2016 09:57:55 +0000 http://www.hindawi.com/journals/ijap/2016/9454730/ Propagation characteristics of oblique incident terahertz wave from the nonuniform dusty plasma are studied using the propagation matrix method. Assuming that the electron density distribution of dusty plasma is parabolic model, variations of power reflection, transmission, and absorption coefficients with frequencies of the incident wave are calculated as the wave illuminates the nonuniform dusty plasma from different angles. The effects of incident angles, number density, and radius of the dust particles on propagation characteristics are discussed in detail. Numerical results show that the number density and radius of the dust particles have very little influences on reflection and transmission coefficients and have obvious effects on absorption coefficients. The terahertz wave has good penetrability in dusty plasma. Yunhua Cao, Haiying Li, Zhe Wang, and Zhensen Wu Copyright © 2016 Yunhua Cao et al. All rights reserved. Connectivity Analysis of Millimeter-Wave Device-to-Device Networks with Blockage Thu, 17 Nov 2016 09:43:53 +0000 http://www.hindawi.com/journals/ijap/2016/7939671/ We consider device-to-device (D2D) communications in millimeter-wave (mm Wave) for the future fifth generation (5G) cellular networks. While the mm Wave systems can support multiple D2D pairs simultaneously through beamforming with highly directional antenna arrays, the mm Wave channel is significantly more susceptible to blockage compared to microwave; mm Wave channel studies indicate that if line-of-sight (LoS) paths are blocked, reliable mm Wave communications may not be achieved for high data-rate applications. Therefore, assuming that an outage occurs in the absence of the LoS path between two wireless devices by obstructions, we focus on connectivity of the mm Wave D2D networks. We consider two types of D2D communications: direct and indirect schemes. The connectivity performances of the two schemes are investigated in terms of (i) the probability to achieve a fully connected network and (ii) the average number of reliably connected devices . Through analysis and simulation, we show that, as the network size increases, and decrease. Also, and decrease, when the blockage parameter increases. Moreover, simulation results indicate that the hybrid direct and indirect scheme can improve both and up to about 35% compared to the nonhybrid scheme. Haejoon Jung and In-Ho Lee Copyright © 2016 Haejoon Jung and In-Ho Lee. All rights reserved. Joint User Scheduling and MU-MIMO Hybrid Beamforming Algorithm for mmWave FDMA Massive MIMO System Thu, 17 Nov 2016 09:35:38 +0000 http://www.hindawi.com/journals/ijap/2016/4341068/ The large bandwidth and multipath in millimeter wave (mmWave) cellular system assure the existence of frequency selective channels; it is necessary that mmWave system remains with frequency division multiple access (FDMA) and user scheduling. But for the hybrid beamforming system, the analog beamforming is implemented by the same phase shifts in the entire frequency band, and the wideband phase shifts may not be harmonious with all users scheduled in frequency resources. This paper proposes a joint user scheduling and multiuser hybrid beamforming algorithm for downlink massive multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) systems. In the first step of user scheduling, the users with identical optimal beams form an OFDMA user group and multiplex the entire frequency resource. Then base station (BS) allocates the frequency resources for each member of OFDMA user group. An OFDMA user group can be regarded as a virtual user; thus it can support arbitrary MU-MIMO user selection and beamforming algorithms. Further, the analog beamforming vectors employ the best beam of each selected MU-MIMO user and the digital beamforming algorithm is solved by weight MMSE to acquire the best performance gain and mitigate the interuser inference. Simulation results show that hybrid beamforming together with user scheduling can greatly improve the performance of mmWave OFDMA massive MU-MIMO system. Jing Jiang and Deting Kong Copyright © 2016 Jing Jiang and Deting Kong. All rights reserved. Mixed-Potential Integral Equation Based Characteristic Mode Analysis of Microstrip Antennas Tue, 15 Nov 2016 06:06:40 +0000 http://www.hindawi.com/journals/ijap/2016/9421050/ A characteristic mode (CM) formulation is developed for the modal analysis of microstrip antennas. It is derived from the mixed-potential integral equation (MPIE) with spatial-domain Green’s functions for multilayered media, where spatial-domain Green’s functions take into account the effect of the multilayered media. The resultant characteristic currents and fields are orthogonal with each other among different orders of modes. Together with the eigenvalues and their deduced indicators, the CMs provide deep physical insights into the radiation mechanisms of microstrip antennas. Numerical results are presented to confirm CM formulation’s effectiveness and accuracy in determining the resonant frequencies, radiating mode currents, and modal fields of microstrip antennas. As opposed to the very popular CM formulation for conducting bodies, comparative studies are presented to show the quite different modal analysis results by considering the multilayered media. Yikai Chen, Liwen Guo, and Shiwen Yang Copyright © 2016 Yikai Chen et al. All rights reserved. A Circular Polarized Rectenna with Out-of-Band Suppression for Microwave Power Transmission Sun, 13 Nov 2016 09:44:39 +0000 http://www.hindawi.com/journals/ijap/2016/8628496/ A novel circular polarized rectenna with out-of-band suppression is proposed in this paper. The circular polarization is realized by corner perturbation on a rectangular radiation patch and enhanced by a diagonal slim slot etched at the center of the patch. An open stub connecting to the quarter wavelength impedance transformer is used to suppress out-of-band wave through harmonics notching. The results of simulations and experiments agree very well, which show that the rectenna obtained −19 dB return loss at 2.4 GHz and −15.5 dB, −18.1 dB, and −11.4 dB suppression on second, third, and fourth harmonic frequency bands, respectively. The reflection coefficient in overall out-of-band, up to 10 GHz, is limited up to −3 dB. Integrated with a voltage doubling rectification circuit, the proposed rectenna can obtain 75.5% RF-to-DC conversion efficiency. Weijun Hong, Yanjie Cao, Li Deng, Shufang Li, Mengmeng Li, and Hongjie Liu Copyright © 2016 Weijun Hong et al. All rights reserved. A General Range-Velocity Processing Scheme for Discontinuous Spectrum FMCW Signal in HFSWR Applications Thu, 10 Nov 2016 11:49:54 +0000 http://www.hindawi.com/journals/ijap/2016/2609873/ Discontinuous spectrum signal which has separate subbands distributed over a wide spectrum band is a solution to synthesize a wideband waveform in a highly congested spectrum environment. In this paper, we present a general range-velocity processing scheme for the discontinuous spectrum-frequency modulated continuous wave (DS-FMCW) signal specifically. In range domain, we propose a simple time rearrangement operation which converts the range transform problem of the DS-FMCW signal to a general spectral estimation problem of nonuniformly sampled data. Conventional periodogram results in a dirty range spectrum with high sidelobes which cannot be suppressed by traditional spectral weighting. In this paper, we introduce the iterative adaptive approach (IAA) in the estimation of the range spectrum. IAA is shown to have the ability to provide a clean range spectrum. On the other hand, the discontinuity of the signal spectrum has little impact on the velocity processing. However, with the range resolution improved, the influence of the target motion becomes nonnegligible. We present a velocity compensation strategy which includes the intersweep compensation and in-sweep compensation. Our processing scheme with the velocity compensation is shown to provide an accurate and clean range-velocity image which benefits the following detection process. Mengguan Pan, Baixiao Chen, and Minglei Yang Copyright © 2016 Mengguan Pan et al. All rights reserved. Study of the Electromagnetic Waves Propagation over the Improved Fractal Sea Surface Based on Parabolic Equation Method Tue, 08 Nov 2016 13:23:23 +0000 http://www.hindawi.com/journals/ijap/2016/8235752/ An improved fractal sea surface model, which can describe the capillary waves very well, is introduced to simulate the one-dimension rough sea surface. In this model, the propagation of electromagnetic waves (EWs) is computed by the parabolic equation (PE) method using the finite-difference (FD) algorithm. The numerical simulation results of the introduced model are compared with those of the Miller-Brown model and the Elfouhaily spectrum inversion model. It has been shown that the effects of the fine structure of the sea surface on the EWs propagation in the introduced model are more apparent than those in the other two models. Wenwan Ding, Kun Wang, and Yunliang Long Copyright © 2016 Wenwan Ding et al. All rights reserved. Design and Investigation of Differential-Fed Ultra-Wideband Patch Antenna with Polarization Diversity Mon, 07 Nov 2016 13:47:29 +0000 http://www.hindawi.com/journals/ijap/2016/4254830/ A novel single- or dual-polarized ultra-wideband (UWB) patch antenna fed by coupled feeding mechanism is proposed. The single-polarized antenna consists of a square ring patch and two Γ-shaped patches which are coupled to the radiating patch. The vertical portions of the Γ-shaped patches are connected to the microstrip lines which are printed on the bottom layer of the grounded FR4 substrate. To realize the differential feeding mechanism for enhancing the polarization purity, a tapered balun is employed to excite the antenna. Further to provide dual linear orthogonal polarizations, another pair of Γ-shaped patches is added in the single-polarized UWB antenna. The dual-polarized UWB antenna prototype can achieve two orthogonal polarizations with an impedance bandwidth ( dB) of 113% and isolation of over 25 dB across the entire frequency band. Yanfang Wang, Fuguo Zhu, and Steven Gao Copyright © 2016 Yanfang Wang et al. All rights reserved. Design of a Dual-Band Bidirectional Antenna Using Superellipse-Monopole-Fed Rectangular Ring for IEEE 802.11 a/b/g/n Applications Mon, 07 Nov 2016 08:46:32 +0000 http://www.hindawi.com/journals/ijap/2016/9368904/ This paper presents the design of a dual-band bidirectional ring antenna fed by a superellipse surface probe for 2.4/5 GHz WLAN applications. The Method of Moments (MoM) with RWG basis function was utilized in the study and design processes. A prototype antenna was fabricated successfully with the advantages of simple and low-cost structure. The measured impedance bandwidth of 810 MHz (2.10–2.91 GHz) and 2.39 GHz (3.57–5.96 GHz) is achieved for the first and second band, respectively. The peak gains are also feasible, 4.67 dBi at 2.45 GHz and 7.83 dBi at 5.5 GHz, with bidirectional radiation patterns for both bands. From the experimental field tests, the proposed antenna was suitable for most applications in long and narrow communication sites in 2.4/5 GHz bands as desired. Also, the measured and calculated results were in good agreement. Ekajit Khoomwong and Chuwong Phongcharoenpanich Copyright © 2016 Ekajit Khoomwong and Chuwong Phongcharoenpanich. All rights reserved. Focusing of Spotlight Tandem-Configuration Bistatic Data with Frequency Scaling Algorithm Sun, 06 Nov 2016 14:17:23 +0000 http://www.hindawi.com/journals/ijap/2016/3251082/ A frequency scaling (FS) imaging algorithm is proposed for spotlight bistatic SAR data processing. Range cell migration correction (RCMC) is realized through phase multiplication. The proposed algorithm is insensitive to the length of the baseline due to the high precision of the point target (PT) spectrum that we are based on. It is capable of handling bistatic SAR data with a large baseline to range ratio. The algorithms suitable for small and high squint angles are both discussed according to whether the range dependence of the second range compression (SRC) can be neglected or not. Simulated experiments validate the effectiveness of the proposed algorithm. Shichao Chen, Ming Liu, Jun Wang, Fugang Lu, and Mengdao Xing Copyright © 2016 Shichao Chen et al. All rights reserved. A Compact Novel Three-Port Integrated Wide and Narrow Band Antennas System for Cognitive Radio Applications Sun, 06 Nov 2016 13:50:13 +0000 http://www.hindawi.com/journals/ijap/2016/2829357/ The design of a three-port radiating structure, integrating wide and narrow band antennas for cognitive radio applications, is presented. It consists of a UWB antenna for spectrum sensing and two narrow band antennas for wireless communication integrated on the same substrate. The UWB antenna covers the complete UWB spectrum (3.1 GHz to 10.6 GHz) approved by FCC. In the two narrow band antennas, each antenna presents dual bands. In particular, the first narrowband antenna resonates at 6.5 GHz, covering the frequency band between 6.36 GHz and 6.63 GHz, and at 9 GHz, covering the frequency band between 8.78 GHz and 9.23 GHz, presenting minimum return loss values of 28.3 dB at 6.5 GHz and 20.5 dB at 9 GHz, respectively. Similarly, the second one resonates at 7.5 GHz, covering the frequency band between 7.33 GHz and 7.7 GHz, and at 9.5 GHz, covering the frequency band between 9.23 GHz and 9.82 GHz, presenting minimum return loss values of 19.6 dB at 7.5 GHz and 28.8 dB at 9.5 GHz, respectively. Isolation among the three antennas is less than −20 dB over the UWB frequency spectrum. These antennas are realized on a FR4 substrate of dimensions 30 mm × 30 mm × 1.6 mm. Experimental results show a good agreement between the simulated and measured results. N. Anvesh Kumar and A. S. Gandhi Copyright © 2016 N. Anvesh Kumar and A. S. Gandhi. All rights reserved. A Fast Algorithm of Generalized Radon-Fourier Transform for Weak Maneuvering Target Detection Sun, 06 Nov 2016 11:09:35 +0000 http://www.hindawi.com/journals/ijap/2016/4315616/ The generalized Radon-Fourier transform (GRFT) has been proposed to detect radar weak maneuvering targets by realizing coherent integration via jointly searching in motion parameter space. Two main drawbacks of GRFT are the heavy computational burden and the blind speed side lobes (BSSL) which will cause serious false alarms. The BSSL learning-based particle swarm optimization (BPSO) has been proposed before to reduce the computational burden of GRFT and solve the BSSL problem simultaneously. However, the BPSO suffers from an apparent loss in detection performance compared with GRFT. In this paper, a fast implementation algorithm of GRFT using the BSSL learning-based modified wind-driven optimization (BMWDO) is proposed. In the BMWDO, the BSSL learning procedure is also used to deal with the BSSL phenomenon. Besides, the MWDO adjusts the coefficients in WDO with Levy distribution and uniform distribution, and it outperforms PSO in a noisy environment. Compared with BPSO, the proposed method can achieve better detection performance with a similar computational cost. Several numerical experiments are also provided to demonstrate the effectiveness of the proposed method. Weijie Xia, Ying Zhou, Xue Jin, and Jianjiang Zhou Copyright © 2016 Weijie Xia et al. All rights reserved. Design and Performance Analysis of MISO-ORM-DCSK System over Rayleigh Fading Channels Sun, 06 Nov 2016 07:15:06 +0000 http://www.hindawi.com/journals/ijap/2016/8459109/ A novel chaotic communication system, named Orthogonality-based Reference Modulated-Differential Chaos Shift Keying (ORM-DCSK), is proposed to enhance the performance of RM-DCSK. By designing an orthogonal chaotic generator (OCG), the intrasignal interference components in RM-DCSK are eliminated. Also, the signal frame format is expanded so the average bit energy is reduced. As a result, the proposed system has less interference in decision variables. Furthermore, to investigate the bit error rate (BER) performance over Rayleigh fading channels, the MISO-ORM-DCSK is studied. The BER expressions of the new system are derived and analyzed over AWGN channel and multipath Rayleigh fading channel. All simulation results not only show that the proposed system can obtain significant improvement but also verify the analysis in theory. Gang Zhang, Chuan gang Wang, Guo quan Li, and Jin zhao Lin Copyright © 2016 Gang Zhang et al. All rights reserved. Spatial and Temporal Characterization of Indoor Millimeter Wave Propagation at 24 GHz Tue, 01 Nov 2016 10:51:45 +0000 http://www.hindawi.com/journals/ijap/2016/2318731/ Indoor millimeter wave propagation at the frequency of 24 GHz is studied by experimental methods. Measurements are performed to obtain temporal and spatial channel model using a channel sounder and rotating antennas in a corridor. The measured impulse responses are processed to obtain compact channel model following Saleh-Valenzuela’s model. The responses are compared with those of 5.3 GHz for the same test sites. Angular spread of 24 GHz is found to be smaller than that of 5.3 GHz, while echoes of 24 GHz are found to be longer than those of 5.3 GHz. Seok-hwan Min, Hayeon Kim, Haengseon Lee, Woo Jin Byun, Minsoo Kang, Kwangseon Kim, Bong-su Kim, and Myung-sun Song Copyright © 2016 Seok-hwan Min et al. All rights reserved. Design of Wideband Dual-Polarized Planar Antenna Using Multimode Concept Sun, 30 Oct 2016 13:04:02 +0000 http://www.hindawi.com/journals/ijap/2016/1286398/ A wideband dual-polarized planar antenna is designed and analyzed by using the theory of characteristic modes (TCM). The eigenvalue, eigencurrent, characteristic pattern, and modal weighting coefficient are analyzed to bring physical insight to this kind of antenna. The results demonstrate that there are two modes resonant in the operating band for each polarization, which have been combined to form a wider frequency band. A bandwidth of 60.2% (1.72–3.2 GHz) for VSWR < 1.5 with high isolation of 32 dB is achieved simultaneously. The size of the radiator structure is 0.33 × 0.33 × 0.22 ( refers to the center operating frequency). Deqiang Yang, Huiling Zeng, Yubo Wen, Meng Zou, and Jin Pan Copyright © 2016 Deqiang Yang et al. All rights reserved. Wideband, Low-Profile, Dual-Polarized Slot Antenna with an AMC Surface for Wireless Communications Sun, 30 Oct 2016 09:41:58 +0000 http://www.hindawi.com/journals/ijap/2016/7641382/ A wideband dual-polarized slot antenna loaded with artificial magnetic conductor (AMC) is proposed for WLAN/WIMAX and LTE applications. The slot antenna mainly consists of two pairs of arrow-shaped slots along the diagonals of the square patch. Stepped microstrip feedlines are placed orthogonally to excite the horizontal and vertical polarizations of the antenna. To realize unidirectional radiation and low profile, an AMC surface composed of 7 × 7 unit cells is designed underneath a distance of ( being the wavelength in free space at 2.25 GHz) from the slot antenna. Both the dual-polarized slot antenna and the AMC surface are fabricated and measured. Experimental results demonstrate that the proposed antenna achieves for both polarizations a wide impedance bandwidth (return loss 10 dB) of 36.7%, operating from 1.96 to 2.84 GHz. The isolation between the two input ports keeps higher than 29 dB whereas the cross-polarization levels basically maintain lower than −30 dB across the entire frequency band. High front-to-back ratios better than 22 dB and a stable gain higher than 8 dBi are obtained over the whole band. Wei Hu, Rui-Na Lian, Zhao-Yang Tang, and Ying-Zeng Yin Copyright © 2016 Wei Hu et al. All rights reserved. Dielectric Resonator Antennas: Basic Concepts, Design Guidelines, and Recent Developments at Millimeter-Wave Frequencies Thu, 27 Oct 2016 14:00:04 +0000 http://www.hindawi.com/journals/ijap/2016/6075680/ An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs) is presented. The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction. Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated. In this way, guidance is provided to radio frequency (RF) front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization. Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies. S. Keyrouz and D. Caratelli Copyright © 2016 S. Keyrouz and D. Caratelli. All rights reserved. Multilayer Brightness Temperature Tracing Method for Rough Surface Scene Simulation in Passive Millimeter-Wave Imaging Thu, 27 Oct 2016 12:40:37 +0000 http://www.hindawi.com/journals/ijap/2016/6763182/ Simulation in passive millimeter-wave (MMW) imaging of rough surfaces is an indispensable step in the simulation in passive radiation imaging, especially for the rough surfaces of different roughness surfaces. However, little attention has been paid to the simulation of rough surface; based on the existing model of brightness temperature tracing described in previous work, diffused reflection of the rough surface is taken into account in the improved model which is presented in this paper. In the paper, the brightness temperature tracing model of different roughness surfaces has been established. Then, we present a method called multilayer brightness temperature tracing (MBTT) method to obtain the radiation brightness temperature of rough surface. Hence, the discrimination of brightness temperature tracing method is enhanced. Chuan Yin, Ming Zhang, and Yaming Bo Copyright © 2016 Chuan Yin et al. All rights reserved.