基于高阶累积量虚拟阵列扩展的DOA估计

该文提出了一种基于高阶累积量虚拟阵列扩展的DOA估计新方法.该方法基于高阶累积量孔径扩展的性质,由实际阵元的坐标与方向矢量直接计算出虚拟阵元的坐标与方向矢量,利用两种阵元的坐标之间的关系构造四阶或六阶协方差矩阵,运用MUSIC方法对非高斯独立信号源进行DOA估计.该方法在任意阵列的情况下,对非高斯独立信号源进行一维与二维DOA估计,均能准确地估计出多于实际阵元数目的方向角与仰角.实验表明,该方法简单、有效地扩展了阵列孔径,提高了阵列的空间分辨能力,有效地抑制了高斯噪声的干扰,降低了高阶累积量协方差矩阵的计算量.     

基于四阶累积过的阵列扩展

在阵列测向问题中应用高阶累积量除了信息利用更充分和抑制高斯噪声等优点之外还具有阵列扩展的功能.本文推导了基于四阶累积量的阵列扩展方法,研究了虚拟阵的结构.放宽了协方差方法对信源数目的限制.但该方法在窄带多信号方向估计应用中存在局限.本文还推导了四阶相干问题和阵列扩展的限制条件.最后给出了实验举例.     

基于四阶累积量的最大似然测向方法研究

论述了最大似然（ML）算法测向以及四阶累积量阵列扩展的基本原理，在此基础上给出了一种基于最大似然算法和四阶累积量的DOA估计新方法。与普通的基于二阶矩的最大似然算法相比，本方法具有对阵列进行四阶扩展的能力，可以解决信号源数大于阵元数时的测向问题，并且由于四阶累积量自身的盲高斯性，还可以有效抑制高斯色噪声。     

一种多径环境下基于四阶累积量的阵列扩展测向方法

本文分析了基于四阶累积量的测向方法不能正确测量多径信号方向的原因，提出了一种多径环境下的基于四阶累积量的新型测向方法。该方法利用零点领处理方法抑制多径信号，然后采用四阶累积量进行阵列扩展测向。计算机模拟结果表明该方法在多径环境下具有良好的性能并且可能实现对足够多的信号进行测向。     

基于虚拟阵列扩展的DOA估计

讨论了基于虚拟阵列扩展的DOA估计问题,对此问题传统阵列处理方法主要利用高阶累积量进行阵列扩展,计算量较大。在四阶矩基础上,通过扩大阵列孔径和自由度解决信源数目较阵元数多的DOA估计问题,利用特殊矩阵对扩展阵列的冗余信息进行剔除,降低了计算复杂度,提高了计算效率。仿真结果验证算法高效可靠,为工程实现提供了理论基础。     

基于四阶累积量虚拟阵列扩展的运算量分析

在阵列信号处理中,利用四阶累积量可以使阵列虚拟扩展,增大了天线阵的孔径,但同时也增加了算法的计算量。该文通过分析四阶累积量矩阵中各元素之间的关系,剔除掉相同或互为共轭的冗余元素,避免了冗余元素的重复计算,极大地降低了四阶累积量矩阵计算的复杂度,并阐述了计算复杂度与阵元数目之间的关系。另外,针对均匀直线阵这种特殊情况进行了单独讨论。该文得出的相关结论对实际工程应用具有指导性的意义。     

一种构造最佳四元二维互补阵列的新方法

该文利用最佳四元二维互补阵列和准最佳四元二维互补阵列的性质,给出了一种构造最佳四元二维互补阵列的新方法.使用这种方法,可以将一个二维的阶的最佳四元二维互补阵列和一个阶的准最佳四元二维互补阵列,构造成新的一类二维阶和阶的最佳四元二维互补阵列.     

高斯色噪声下的相干信号 DOA 高分辨率估计*

针对高斯有色噪声下的DOA估计问题,提出一种基于高阶累积量稀疏表示的DOA估计方法。该方法利用四阶累积量矩阵中的第一列生成最小冗余向量,利用扩展阵列的最小冗余导向矢量构造过完备字典。然后利用L1范数作为稀疏约束条件,建立最小冗余向量的稀疏模型进行DOA估计。该方法将求解四阶累积量的次数从M4次降为M2-M+1次。同时又能充分利用四阶累积量的优点,对高斯有色噪声具有良好的抑制能力,并使阵列孔径得到了扩展,估计信号个数能大于阵元数目。仿真实验和理论分析验证了该方法比MUSIC-like和MUSIC算法具有更好的性能,不需要任何处理可以直接应用到相干信号。     

基于四阶累积量扩展孔径的线阵设计

阵列孔径越大,空间谱分辨率越高.在借鉴传统的约束最小冗余线阵概念的基础上,从阵列输出的四阶累积量定义出发,利用四阶累积量扩展阵列孔径的功能,设计出基于四阶累积量的约束最小冗余线阵.与相同阵元数的传统约束最小冗余线阵相比,它具有大得多的有效孔径,从而在运用四阶累积量DOA估计方法时可大大增加可估计的信号数,极大地提高DOA估计分辨率.仿真结果证明了结论.     

基于四阶累积量扩展孔径的宽带信源测向算法

当阵列过载时,常用高分辨测向算法将会失效.针对此问题,提出了一种新的宽带信源测向算法.该算法利用基于最小冗余直线阵列的四阶累积量来扩展阵列孔径.将得到的四阶累积量去除冗余信息后,构造了一新的Toeplitz矩阵.新矩阵充分利用了原协方差矩阵的信息,避免了冗余信息.通过理论分析和计算机仿真,对扩展后阵列孔径、测向性能、检测概率及可分辨信源数进行了对比研究.结果表明,相比相同阵元数的最小冗余直线阵和均匀直线阵,该算法具有大得多的阵列孔径和更高的分辨率,利用M阵元,最多可以分辨M2-M个信源.     

ANTENNA ARRAY PATTERN NULL STEERING——A THEORETICAL INTRODUCTION

The antenna array pattern null steering is one of the important current topics in the array synthesis theory, due to it's very effectiveness to suppress the interfering signals. Thus in this paper the problem of forming nulls in the radiational pattern of three-dimensional arrays is discussed. This paper deals with the following aspects: The essential relations forming multi-nulls in the arrays are analysed by the method of vector space. A method forming multi-null regions is presented in terms of the extensive property of null itself. The resolvent formulation of the radiational pattern of multi-null steering is derived. The numerical results are given and discussed. The resolvent formulation is analogous to the one of the adaptive arrays.     

The root-trajectory method--A tool for analyzing linear adaptive arrays

A root-trajectory method is described that seeks to obviate the need for an extensive set of antenna patterns to describe the behavior of an adaptive array during its adaptation process. This aim is achieved by use of Schelkunoff's idea of describing a linear array in terms of an array polynomial. The roots of this polynomial have a direct interpretation in obtaining the array gain, and the trajectories of these roots during the adaptation process give a simple visualization of the dynamic behavior of the adaptive array.     

一种三通道权微扰谱估计测向方法

介绍了一种三通道权微扰谱估计测向方法。该方法首先利用权微扰方法来获得阵列的协方差矩阵,进而采用特征结构类算法估计波达方向,并采用空间平滑算法来处理相干信源。仿真结果表明,该方法的估计结果更加稳健、有效。且在接收机数目较少的情况下,该方法仍具有一定的实用性。     

FD-TD analysis of Vivaldi flared horn antennas and arrays

This paper summarizes a detailed computational study of Vivaldi flared horn antenna designs including single element, double element crossed-pair subarray elements, and linear arrays using the finite-difference time-domain (FD-TD) method. FD-TD, which numerically solves Maxwell's time dependent curl equations, accounts for the complex geometrical and electrical characteristics associated with this antenna design and array implementation. Validations have been made relative to a moment method (MM) model of an electrically large linearly tapered slot antenna. Also, good correlation is shown to exist in the primary features of the antenna patterns between computed and measured data for all cases. This work has achieved a number firsts for the FD-TD methodology. It represents the first “exact” computational model of a single quad Vivaldi slot antenna; the first “exact” computational model of a phased array of Vivaldi quad elements; and the first FD-TD model to demonstrate grating lobes for a phased array antenna of any sort. Lastly, this research represents an extensive study of the largest grid-based antenna models conducted to date     

Coherent acoustic array processing and localization on wireless sensor networks

Advances in microelectronics, array processing, and wireless networking have motivated the analysis and design of low-cost integrated sensing, computing, and communicating nodes capable of performing various demanding collaborative space-time processing tasks. In this paper, we consider the problem of coherent acoustic sensor array processing and localization on distributed wireless sensor networks. We first introduce some basic concepts of beamforming and localization for wide-band acoustic sources. A review of various known localization algorithms based on time-delay followed by least-squares estimations as well as the maximum-likelihood method is given. Issues related to practical implementation of coherent array processing, including the need for fine-grain time synchronization, are discussed. Then we describe the implementation of a Linux-based wireless networked acoustic sensor array testbed, utilizing commercially available iPAQs with built-in microphones, codecs, and microprocessors, plus wireless Ethernet cards, to perform acoustic source localization. Various field-measured results using two localization algorithms show the effectiveness of the proposed testbed. An extensive list of references related to this work is also included.     

Direction of Arrival Estimation of Multiple UWB Signals

This paper deals with the problem of estimation of direction of arrivals (DOA) of a multiple ultra-wideband (UWB) pulse postion modulation signals incident on a smart antenna in the presence of white Gaussian noise. We transform the received signal into frequency domain in order to split the array output into multiple frequency channels. Corresponding frequency channels data of the array is arranged into a model similar to narrowband DOA estimation. Iterative quadratic maximum likelihood algorithm is applied to yield DOA estimates. These separate estimates at different frequencies are combined into a single estimate of DOA for each source in an appropriate manner. The performance of the proposed method is studied via extensive computer simulations. It is seen that the technique can successfully resolve the DOA of the closely-spaced UWB signals.     

VOD中的层次化存储结构分析与设计

为适应大规模VOD系统的要求 ,提出了基于磁盘阵列和光盘库的层次化存储结构 ,并分析了 3级光盘库的RR节目调度算法。     

薄板中的光声相控阵聚焦技术研究

光声技术以其声源空间分辨率高,易于产生而受到广泛关注,但因光声转化效率低下,如何利用多点光声产生声聚焦成为提高光声检测灵敏度的重要途径。为了利用多点光声产生声聚焦以提高光声检测灵敏度,该文开展了基于八阵元的光声声聚焦的研究。利用时间反转法,采用仿真加实验的方法,分析了空间激励位置、频率及阵元数对聚焦性能的影响。实验结果表明,该方法实现了10倍以上的聚焦效果。     

Scattering of a plane electromagnetic wave by a linear array of cylindrical elements

An approximate method for numerically calculating the scattered field of a linear array of center-loaded cylindrical elements illuminated by a plane wave incident in theHplane of the array is described. To illustrate the use of the approximation technique, theH-plane scattered field of an eight-element model array is calculated for various conditions of impedance loading and illumination. From extensive calculations, it is found that theHplane scattered field of the array can be represented approximately by the product of the electric field scattered in the reflected direction and an interference factor. The interference factor is the equivalent of the complex array factor of the model array when excited with uniform amplitude and an element-to-element phase progression proportional to the sine of the angle of incidence of the illumination.     

Effects of modeling errors on the resolution threshold of the MUSICalgorithm

Subspace-based algorithms for narrowband direction-of-arrival (DOA) estimation require detailed knowledge of the array response (the array manifold) and assume that the noise covariance matrix is known up to a scaling factor. In practice, these quantities are not known precisely. Estimation accuracy can degrade significantly when the array response or the noise covariance deviate from their nominal values. In the paper the authors examine the resolution threshold of the MUSIC algorithm when the array response is perturbed from its assumed value and when the noise covariance does not match the assumed model. Analytical expressions for the resolution threshold are derived and verified by computer simulation. The authors also demonstrate the fact that preprocessing of the array data can improve somewhat the resolution in the presence of model errors. The paper makes extensive use of the contributions of various authors