均匀线阵互耦矩阵非Toeplitz条件下的DOA估计

理想条件下,均匀线阵的互耦矩阵可用一带状、对称Toeplitz矩阵进行建模。然而实测数据表明,均匀线阵的互耦矩阵具有对称性,但不具有Toeplitz性,此时仍按理想情况建模,会导致DOA估计不准甚至完全失效。基于RBF神经网络,提出了互耦矩阵非Toeplitz条件下的DOA估计方法。算法利用了信号协方差矩阵的对称性和对角线元素不含信号DOA信息的特点,取协方差矩阵的上三角的元素作为网络输入,不仅减少了网络的输入数,同时还提高了与阵列法线夹角60°外的DOA估计精度。实验仿真结果验证了算法的有效性。     

一种分析多目标电磁特性的快速方法

针对传统RWG矩量法分析电大或阵列目标耗时长的问题,提出将等效偶极子法(Equivalent Dipole-moment Method,EDMM)和特征基函数法(Characteristic Basis Function Method,CBFM)结合起来对其进行分析,利用EDMM计算中距离基函数对的互耦效应,再利用CBFM计算远距离基函数对之间的互耦作用,不仅简化了阻抗矩阵元素的求解,而且加快了阻抗矩阵的求逆过程。通过该方法对一多目标阵列的散射特性进行了分析,能在保证计算结果精度的同时大大缩减运算的时间,从而体现了该方法的准确性和实用性。     

阵列误差影响下的RBF神经网络波达方向估计

针对阵列误差(阵元间互耦、通道失配)影响下波达方向估计问题,提出一种新型的基于径向基神经网络侦察测向系统。这种系统采用直接数据域补偿算法对输入数据进行误差补偿,从而获得正确的基函数中心。在无需对RBF神经网络测向系统作任何改进的情况下,可获得对波达方向的准确估计。为了减少输入,利用信号协方差矩阵的对称性以及对角线元素不包含信号方向信息的特点,仅考虑协方差矩阵中的上三角部分元素作为网络输入。给出了应用该方法的具体步骤。仿真实验表明,基于这种RBF网络的侦察测向系统达到了很高的精度。     

智能天线波达方向的互耦影响与修正

智能天线中阵列互耦的存在,严重影响了自适应天线的性能.基于分析天线阵列模型中阵元间的相互关联的特征的方法,构造互耦矩阵C,用C矩阵来修正波达方向估算中的互耦,并在MUSIC算法中实现.该方法理论分析与计算仿真表明该算法切实可行,有效并易于实现.     

一种互耦和相干源条件下的DOA估计方法

空间平滑算法是一种常用的解相干处理方法,而阵元间互耦的存在会导致空间平滑算法失效,从而无法准确估计相干源DOA。针对这个问题,文中提出了一种新的DOA估计方法。该方法基于信号子空间和噪声子空间的正交性原理,利用入射信号源中的独立信号源可以有效估计出互耦矩阵,再通过估计的互耦矩阵对接收数据协方差矩阵进行互耦补偿,克服了互耦对空间平滑算法的影响,从而保证了相干源DOA能准确估计。计算机仿真实验表明了该方法的有效性。     

波达方向估计的一种互耦修正方法

阵列天线中互耦的存在,严重影响了天线的性能。基于分析天线阵列模型中阵元间的相互关联的特征的方法,构造互耦矩阵C,用C矩阵来修正波达方向估算中的互耦,并在MUSIC算法中实现。理论分析与计算仿真均表明该算法切实可行,有效并易于实现。     

一种阵列互耦矩阵与波达方向的级联估计方法

当阵列天线存在互耦效应时,传统多重信号分类(MUltiple SIgnal Classification, MUSIC)算法的测向性能急剧下降。为了有效估计阵列互耦矩阵(MCM)与入射信号的波达方向(Direction Of Arrival, DOA),该文提出一种阵列互耦矩阵与波达方向的级联估计方法。利用互耦矩阵的结构特点,变换阵列流形,实现对互耦矩阵与DOA的解耦合。求解线性约束下的二次优化问题,利用谱峰搜索,得到阵列互耦矩阵和入射信号DOA,完成互耦误差自校正。通过计算机仿真验证了该文方法估计性能的有效性和优越性。     

缝隙阵列天线DOA估计的互耦影响与修正

互耦的存在严重影响了DOA估计的精度，文中研究了存在互耦情况下的DOA估计问题，重点讨论了阵列单元互耦效应的有效计算和对MUSIC算法的修正问题；以缝隙阵列天线为例，通过对无限阵散射参量的修正得到有限阵的散射矩阵和阻抗矩阵，进而通过阻抗矩阵估计互耦的影响，并对MUSIC算法进行修正，最后给出了仿真结果。     

互耦效应下用单快拍数据实现相干信源完全解相干和解耦合

阵元间存在互耦时,会对阵列流型产生扰动,同时当空间来波存在相干信源时,协方差矩阵会产生秩亏,这两类问题都会使子空间类估计算法性能急剧下降甚至失效。针对互耦效应下的解相干问题,该文提出了一种仅利用阵列单快拍即可实现完全解相干和解互耦算法互耦效应下的修正单次快拍算法(MC-ENDTOP)。该方法将原单快拍算法应用背景推广至任意形式来波信号,利用一次快拍构造等效接收数据协方差矩阵,通过数据分解,将互耦系数从阵列流型矩阵中剥离,从而实现了完全解互耦,并将其归入分解后的等效信号协方差矩阵中,由于等效信号协方差矩阵为对角阵,且对角元素与信号相关性无关,因此进一步实现了完全解相干。仿真验证了该文算法能够抑制互耦影响,估计性能和无互耦时相当,且适用于实时性要求高的场合。     

线性阵列互耦矩阵和波达方向的联合估计

 针对线性阵列中因存在互耦效应导致很难直接估计信号波达方向的问题,结合线性阵列的阻抗特性,针对均匀线阵提出了一种计算量更小、稳健性更强的互耦矩阵和波达方向的联合估计方法.并把该方法推广到一般的线性阵列,解决了互耦条件下线阵的测向问题.仿真结果验证了这种新的联合估计方法在均匀线阵中的性能改进情况,以及向一般线阵扩展模型的可用性.     

Bearing estimations with mutual coupling present

Estimating angles of arrival of radiation sources using an antenna array with mutual coupling between elements is investigated. The presence of mutual coupling distorts phase vectors of radiation sources and the eigenstructure of the covariance matrix. Two approaches are proposed to counteract that distortion so that eigenstructure methods can perform well. The method described first eliminates the distortion of the signal component of the the covariance matrix and then applies spatial smoothing to decorrelate the coherence between sources. Computers simulation results show that this method successfully counteracts mutual coupling     

DOA estimation and self-calibration algorithm for uniform circular array

Based on the banded circulate and symmetric Toeplitz model for the mutual coupling of a uniform circular array, a decoupling direction of arrival (DOA) estimation and self-calibration algorithm is proposed. The new algorithm provides an accurate DOA estimation without the knowledge of mutual coupling. In addition, the mutual coupling coefficients for array self-calibration can be achieved simultaneously. Instead of multidimensional nonlinear search or iterative computation, the algorithm only uses a one-dimensional search and can reduce the computation burden. Simulation results demonstrate the validity of the proposed method.     

共享孔径交错稀疏阵列天线互耦误差建模与校正

共享孔径交错稀疏阵列天线是实现多功能阵列天线的有效途径。现有的参数化互耦消除方法都是针对均匀阵列天线展开的,其研究的互耦矩阵都是规则的方阵,对共享孔径交错稀疏阵列天线的互耦矩阵模型并不适用。在充分考虑共享孔径交错稀疏阵列天线中子阵内互耦的“稀疏”和“方位依赖”的特殊性后,通过将常规的互耦矩阵扩展表示为“非方”的“增广互耦矩阵”来对交错稀疏阵列天线子阵内和子阵间的耦合效应进行建模,并通过“增广互耦矩阵”的参数化估计最终实现了共享孔径交错稀疏阵列天线互耦误差的建模与校正。仿真结果证实了所提方法的有效性和可行性。     

多子阵互耦影响下的非圆信号自校正算法

针对多子阵互耦影响下的非圆信号波达方向(Direction-Of-Arrival,DOA)估计问题,给出了一种针对最大非圆率信号的互耦自校正算法.该算法利用均匀线阵互耦矩阵的带状、对称Toeplitz性和多子阵互耦矩阵的块状对角特性,能够与传统的互耦秩减估计器一样避免多维搜索和迭代运算.并且通过结合信号的非圆特性来扩展数据模型,使得其估计精度较传统的互耦秩减估计算法有明显提升,可分辨信源数也有所增加.对该算法的理论性能进行研究,分析了其对未知参数的可辨识性必要条件,并基于最大非圆率信号模型给出了相应的克拉美罗界(Cramér-Rao Bound,CRB).仿真结果表明,该算法较传统的互耦秩减估计算法在低信噪比、小快拍数下有更强的鲁棒性.     

阵列天线散射条件下的互耦校正

当阵列存在近场散射源时,互耦效应的分析和校正更加繁杂,这就导致了阵列互耦矩阵的参数化建模需要做进一步的扩展,使得互耦矩阵不再为方阵。然而现有的参数化互耦校正方法均假设互耦矩阵是一个具有特殊数学结构的方阵,对非方阵的互耦矩阵模型不适用。本文通过引入少量远离阵列且相互间隔较远的辅助阵元（互耦效应可以忽略）和方向未知的校正信源,提出了一种阵列天线散射条件下的互耦校正的参数估计算法。首先,推导了扩展后的非方阵互耦矩阵系数与方位依赖的幅相误差的等价关系;然后,对每次单源实验,得到校正源方位和各阵元方位依赖的幅相误差的联合估计,建立估计的幅相误差以非方阵互耦系数为参数的方程;最后,将多次单源校正得到的方程进行整合构建方程组,利用Tikhonov正则化方法求解不适定方程组实现互耦系数的有效估计,进而对阵列互耦进行校正。计算机仿真实验结果表明所提算法可以很好地解决阵列天线散射条件下的互耦校正问题,从而验证了算法的有效性。      

A Novel Online Mutual Coupling Compensation Algorithm for Uniform and Linear Arrays

In this paper, a novel online mutual coupling compensation algorithm especially tailored to uniform and linear arrays is presented. It is conceived to simultaneously compensate for mutual coupling and estimate the direction-of-arrivals (DOAs) of signals impinging on the array since the estimated calibration matrix can be embedded within any classical super-resolution direction-finding method. An alternating minimization procedure based on closed-form solutions is performed to estimate the mutual coupling matrix in the field of complex symmetric Toeplitz matrices. Unlike many existing array calibration methods, it requires neither the presence of calibration sources nor previous calibration information as initialization. Computer simulations show the effectiveness of the proposed technique and prove that the nice statistical properties of classical super-resolution DOA estimation algorithms can be restored despite the presence of mutual coupling     

Compensation for the mutual coupling effect for the ESPRIT algorithm in single snapshot array processing

An effective method is introduced to compensate the effects of mutual coupling for the Estimation of Signal Parameter via Rotational Invariance Techniques (ESPRIT) direction finding algorithm in application of signal snapshot array processing.Changing the covariance matrix into a Teoplitz matrix can achieve high resolution in the Direction Of Arrive (DOA) estimation.How the mutual coupling affects the array antennas has been discussed and a new definition of mutual im- pedance has been used to characterize the mutual coupling effects between the array elements.Based on the new mutual impedance matrix,a practical method is presented to eliminate the effects of mutual coupling for ESPRIT in the single snapshot data processing.The simulation results show that, this new method not only properly reduces the effects of mutual coupling,but also maintains its steady performance even for weak signals.     

Hardware realization of inverse kinematics for robot manipulators

For real-time processing of kinematic information required for intelligent robotic applications, a hardware realization of an inverse kinematics algorithm is a challenging task. This paper adopts an incremental unit computation method to accomplish the inverse kinematics of a three-axis articulated robot. This method starts from defining incremental units in joint and Cartesian spaces, which represent the position resolutions in each space. With this approach, calculation of the inverse Jacobian matrix can be realized through a simple combinational logic gate circuit. Furthermore, the incremental direct kinematics can be solved by using a digital differential analyzer (DDA) integrator. The hardware architecture to implement the algorithm is also described. Applying the hardware implemented by an erasable programmable logic device (EPLD) to the straight-line trajectory of an experimental robot, the authors have obtained an end-effector's maximum speed of 12.6 m/s     

Array design for a specified pattern by matrix methods

A new method is presented for designing arrays of parallel wire antennas. The method relates a desired pattern with required feed voltages such that mutual coupling is taken into account in the design procedure. The technique uses matrix methods together with results of the "Method of Moments" to determine the self- and mutual impedances and the required excitations. The design method can be applied to circular, elliptical, and other planar arrays although attention is restricted here to linear arrays. The feed points and the array geometry must be specified.