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Localization of Narrow Band Sources in the Presence of Mutual Coupling via Sparse Solution Finding
Ying Zhang;Qun Wan;An-Ming Huang
PIER , 2008, DOI: 10.2528/PIER08090703
Abstract: Making use of the Toeplitz structure of the mutual coupling matrix of the Uniform Linear Array (ULA), estimating the direction-of-arrival (DOA) of the sources as well as the mutual coupling coefficients of the array can be formulated as a linear inverse problem, where the solution is given by the Kronecker product of the vectors with respect to the DOAs and the mutual coupling coefficients. Through mathematical manipulation, these solution vectors can be decoupled. Estimation of the DOAs is cast into the framework of sparse solution finding. To derive the solution, an alternating minimization technique is presented. The proposed method is firstly developed based on the noise free observation covariance matrix, and can be generalized to directly using the snapshots. Using the proposed method, DOA estimation is feasible even in single snapshot case. The performance of the proposed methods with covariance matrix, single snapshot and multiple snapshots are illustrated by computer simulations. Their ability to resolve closely spaced targets and the applicability to correlated sources have also been demonstrated.
AR Model-Based Direction-of-Arrival Estimation of Coherent Signals in the Presence of Unknown Mutual Coupling  [PDF]
Zhi-Chao Sha,Zhang-Meng Liu,Zhi-Tao Huang,Yi-Yu Zhou
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/386367
Abstract: This paper addresses the problem of direction-of-arrival (DOA) estimation of coherent signals in the presence of unknown mutual coupling, and an autoregression (AR) model-based method is proposed. The effects of mutual coupling can be eliminated by the inherent mechanism of the proposed algorithm, so the DOAs can be accurately estimated without any calibration sources. After the mixing matrix is estimated by independent component analysis (ICA), several parameter equations are established upon the mixing matrix. Finally, all DOAs of coherent signals are estimated by solving these equations. Compared with traditional methods, the proposed method has higher angle resolution and estimation accuracy. Simulation results demonstrate the effectiveness of the algorithm. 1. Introduction Direction-of-arrival (DOA) estimation is very important in a variety of wireless communication applications, such as mobile communication, radar, and distributed sensor networks. In particular, many effective high-resolution DOA estimation algorithms have been developed and deeply investigated in the last decades [1]. Since then, the attention of the signal processing community has focused on the factors that block the practical application of those algorithms. The first factor is the unknown mutual coupling, which will affect the array manifold of the array and result in poor accuracy of DOA estimation [2]. The other factor is that there may be highly correlated or coherent signals because of multipath propagation [3, 4]. When the incident signals are highly correlated or coherent in the presence of unknown mutual coupling, the performance of conventional high-resolution DOA estimation methods will deteriorate significantly. In the last years, many array calibration algorithms have been proposed with respect to the mutual coupling effect [5–13]. Hung [5] uses an iterative least mean-square approach to estimate the calibration matrix, but it requires a preliminary calibration. The above algorithms may not be easily carried out in practice, because of the additional calibration sources or sensors. An iterative algorithm is given to compensate the mutual coupling and perturbation of gain and phase in [6]. However, the convergence rate is slow, and computational cost is very expensive. In [7], a novel online mutual coupling compensation algorithm is presented to estimate coupling parameters through an alternating minimization technique, but the convergence is not well guaranteed. In [8], an algorithm that applies a group of auxiliary sensors in uniform linear arrays (ULAs) has been
CPW Fed Double T-Shaped Array Antenna with Suppressed Mutual Coupling  [PDF]
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.32027
Abstract: A compact CPW-fed double T-Shaped antenna is proposed for dual-band wireless local area network (WLAN) operations. For the proposed antenna, the -10 dB return loss bandwidth could reach about 25.5% for the 2.4 GHz band and 5.7 % for the 5 GHz band, which meet the required bandwidth specification of WLAN standard. To reduce the mutual coupling and get high isolation between two dual-band antennas, we proposed the novel electromagnetic band gap (EBG) structures. When the EBG structure is employed, a -13dB and -30dB mutual coupling reduction is achieved at 2.4 and 5.2 GHz. It shows that the features of small size, uniplanar structure, good radiation characteristics and small mutual coupling are promising for multi-input multi-output (MIMO) applications.
Novel two-dimensional DOA estimation with L-shaped array  [cached]
Xiaofei Zhang,Jianfeng Li,Lingyun Xu
EURASIP Journal on Advances in Signal Processing , 2011,
Abstract: Two-dimensional (2D) direction-of-arrival (DOA) estimation has played an important role in array signal processing. In this article, we address a problem of bind 2D-DOA estimation with L-shaped array. This article links the 2D-DOA estimation problem to the trilinear model. To exploit this link, we derive a trilinear decomposition-based 2D-DOA estimation algorithm in L-shaped array. Without spectral peak searching and pairing, the proposed algorithm employs well. Moreover, our algorithm has much better 2D-DOA estimation performance than the estimation of signal parameters via rotational invariance technique algorithms and propagator method. Simulation results illustrate validity of the algorithm.
Antenna Array Beamforming in the Presence of Spatial Information Uncertainties
Ju-Hong Lee;Guo-Wei Jung;Wen-Chieh Tsai
PIER B , 2011, DOI: 10.2528/PIERB11033017
Abstract: This paper deals with adaptive antenna array beamforming under spatial information uncertainties including steering angle mismatch, random perturbations in array sensor positions, and mutual coupling between antenna array sensors. To make antenna array beamformers robust against the spatial information uncertainties, we present an iterative method to obtain an appropriate estimate of the actual direction vector for each of the desired signals. The proposed method uses only the a posteriori information of the received array data. It invokes an appropriate objective function for estimation and solves the minimization of the objective function by using a gradient based algorithm. The convergence property of the proposed method is investigated. Simulation results are provided for showing the effectiveness of the proposed method.
Effects of Ground Constituent Parameters on Array Mutual Coupling for DOA Estimation  [PDF]
Irfan Ahmed,Warren F. Perger,Seyed A. Zekavat
International Journal of Antennas and Propagation , 2011, DOI: 10.1155/2011/425913
Abstract: Effects of ground constituent parameters on the mutual coupling (MC) of monopole antenna array are investigated. This work augments an existing MC compensation technique for ground-based antennas and proposes reduction in mutual coupling for antennas over finite ground as compared to the perfect ground. The work is investigated by finite element method analysis, and numerical results are presented. A factor of 4 decrease in both the real and imaginary parts of the mutual coupling is observed when considering a poor ground versus a perfectly conducting one, for quarter-wave monopoles in receiving mode. A simulated result to show the errors in direction-of-arrival (DOA) estimation with actual realization of the environment is also presented. 1. Introduction There is an emerging trend in wireless applications such as safety and security, command, and control MIMO communication, that require antennas with direction-of-arrival (DOA) and beamforming capability. In order to support DOA estimation and beamforming, antenna arrays are used. Traditionally, antenna arrays consist of closely located antenna elements that are uniformly distributed across the array. To determine DOA, several techniques have been developed [1]. These techniques frequently assume that the sensors are ideal and operate in an isolated environment. In practice, however, this is not true. The real antenna elements not only interact with each other (MC) but also with the surroundings. This results in the distortion of the signal and causes error in DOA estimation. Several techniques have been proposed to overcome the errors due to antenna MC. These techniques are in the process of development, but can be classified in terms of autocalibration [2–4], open circuit voltage method [5], numerical techniques [6–8], offline calibration [9], and receiving mutual impedance methods [10]. In general, these techniques do not consider the interaction of the antenna array with an imperfect ground in the near zone [11]. Effects of ground proximity and constituent parameters on wire antennas have been presented in the literature [12–14]. This paper considers the effects of ground on the MC of an array of monopoles and impact on DOA estimation. Monopole antennas that take advantage of image theory are ideally placed above a perfect ground of conductivity and relative permittivity . The real ground or earth has finite conductivity and may have high permittivity. The effects of ground constituent parameters on MC and ultimately on DOA estimation are investigated. The evaluation of MC is an extension of the
Microstrip Array Antenna with New 2D-Electromagnetic Band Gap Structure Shapes to Reduce Harmonics and Mutual Coupling
Dalia Mohammed Nasha Elsheakh;Magdy F. Iskander;Esmat Abdel-Fattah Abdallah;Hala A. Elsadek;Hadia Elhenawy
PIER C , 2010, DOI: 10.2528/PIERC09112008
Abstract: This paper presents microstrip array antenna integrated with novel shapes of 2D-electromagnetic band-gap structure (2D-EBG). Three different shapes of 2D EBG are used for harmonic suppression, optimizing the current distribution on the patches and decreasing the mutual coupling between array elements. As a result, the performance of the antenna array is improved. The three novel shapes of 2D-EBG presented are star, H shaped and I shaped slots. Simulated and measured results verify the improved performance of the array antenna compared to the antenna without EBG as well as antenna array with conventional EBG shapes. The harmonic suppression and reflection coefficients are improved by about 18 dB. Minimum mutual coupling is less than -20 dB, and the antenna size is reduced by 15% compared to the original size.
Fast Signal Recovery in the Presence of Mutual Coupling Based on New 2-D Direct Data Domain Approach  [cached]
Azarbar Ali,Dadashzadeh GR,Bakhshi HR
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: The performance of adaptive algorithms, including direct data domain least square, can be significantly degraded in the presence of mutual coupling among array elements. In this paper, a new adaptive algorithm was proposed for the fast recovery of the signal with one snapshot of receiving signals in the presence of mutual coupling, based on the two-dimensional direct data domain least squares (2-D D3LS) for uniform rectangular array (URA). In this method, inverse mutual coupling matrix was not computed. Thus, the computation was reduced and the signal recovery was very fast. Taking mutual coupling into account, a method was derived for estimation of the coupling coefficient which can accurately estimate the coupling coefficient without any auxiliary sensors. Numerical simulations show that recovery of the desired signal is accurate in the presence of mutual coupling.
Mutual Coupling Effects for Radar Cross Section (RCS) of a Series-Fed Dipole Antenna Array  [PDF]
H. L. Sneha,Hema Singh,R. M. Jha
International Journal of Antennas and Propagation , 2012, DOI: 10.1155/2012/601532
Abstract: The estimation of RCS of a phased array depends on various parameters, namely, array geometry, operational frequency, feed network, mutual coupling between the antenna elements and so fourth. This paper presents the estimation of RCS of linear dipole array with series-feed network by tracing the signal path from the antenna aperture into the feed network. The effect of mutual coupling exhibited by the dipole antenna is considered for three configurations namely, side by side, collinear, and parallel in echelon. It is shown that the mutual coupling affects the antenna pattern (and hence RCS) significantly for larger scan angles. Further it is inferred that the RCS of phased array can be optimized by (i) reducing the length of the dipole, (ii) termination of the isolation port of the coupler with a suitable load, and (iii) using suitable amplitude distribution. 1. Introduction Radar Cross Section (RCS) of an aerospace vehicle significantly depends on the scattering of the signals by the antenna array mounted on it [1]. This antenna mode scattering is dependent on (i) geometry of the phased array, (ii) nature of the feed network employed to excite it, and (iii) mutual coupling effect. In general a phased array requires a feed network in order to function as an effective receiver or transmitter. This feed network comprises of radiating elements, phase shifters, couplers, and the terminating resistors. Depending on their mode of arrangement, the feed network may be categorized as series feed, corporate feed and space feed [2, 3]. In order to design a series-fed phased array with specific desired characteristics several factors like the number of elements, their Interelement spacing, and beam scan angle are to be considered. Further if the spacing between the elements is less than half-wavelength, the effects of mutual coupling become predominant. These parameters of the array design are found to affect the RCS of the target considerably [4]. Mutual coupling has its influence on the impedance of the array elements, reflection coefficients, radiation pattern, and thus the RCS of phased array [5]. Every element in the antenna array will be of a definite physical size and shape. The signal incident on each of these elements will be reradiated due to various reasons like manufacturing defects, mismatches in the network, and so forth. The fields radiated from one antenna element interact with the field of the surrounding antennas which give rise to coupling. These reradiated fields when scattered along different directions affect the RCS of the target
Accurate DOA Estimations Using Microstrip Adaptive Arrays in the Presence of Mutual Coupling Effect  [PDF]
Qiulin Huang,Hongxing Zhou,Jianhui Bao,Xiaowei Shi
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/919545
Abstract: A new mutual coupling calibration method is proposed for adaptive antenna arrays and is employed in the DOA estimations to calibrate the received signals. The new method is developed via the transformation between the embedded element patterns and the isolated element patterns. The new method is characterized by the wide adaptability of element structures such as dipole arrays and microstrip arrays. Additionally, the new method is suitable not only for the linear polarization but also for the circular polarization. It is shown that accurate calibration of the mutual coupling can be obtained for the incident signals in the 3?dB beam width and the wider angle range, and, consequently, accurate [1D] and [2D] DOA estimations can be obtained. Effectiveness of the new calibration method is verified by a linearly polarized microstrip ULA, a circularly polarized microstrip ULA, and a circularly polarized microstrip UCA. 1. Introduction In the last several decades, many direction-of-arrival (DOA) estimation algorithms with superresolution have been proposed, such as the multiple signal classification (MUSIC), the estimations of signal parameters via rotational invariance techniques (ESPRIT), the maximum likelihood (ML), and the subspace fitting (SF) [1–4]. Employing the ideal array manifold, these algorithms can provide excellent DOA estimation performances. For the actual antenna array, however, the array manifold cannot be regarded as that of the ideal point source array. The magnitude and phase of the received array signals are disturbed by the mutual coupling effect of the actual array, which would degrade the performances of the DOA estimation algorithms [5]. Many interests have been focused on the DOA estimations in the presence of mutual coupling effect over the past years. In order to obtain accurate DOA estimations, DOA estimation methods employing the actual array manifold were proposed [6–8]. Essentially, the actual manifold is equivalent to the array pattern. However, great effort is required to calculate and measure the actual manifold. Additionally, mass storage is needed for the manifold data in these methods. The transformation relationship between the actual array manifold and the array manifold of the ideal point source was proposed to decrease the storage of the manifold data [9, 10]. In this method, a distortion matrix was employed to carry out the transformation with assuming that the distortion matrix is angular independent. The validity of this method was verified in the 1D DOA estimations using the antenna array composed of the collinear
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