多跳频信号波达方向与极化状态联合估计算法

为了有效辅助跳频(FH)网台分选和信号识别、跟踪,该文用正交偶极子对构造极化敏感阵列,基于空间极化时频分析,在欠定条件下实现了多跳频信号波达方向(Direction Of Arrival, DOA)与极化状态的高效联合估计。首先建立跳频信号的极化敏感阵列观察模型,然后根据参考阵元时频分析结果建立各跳信号的空间极化时频分布矩阵,再利用该矩阵中蕴含的信号极化-空域特征信息分别运用线性、二次型空间极化时频以及多项式求根共3种方法实现DOA与极化参数联合估计,最后蒙特卡罗仿真结果验证了该算法的有效性。     

基于电磁矢量传感器的MIMO天线阵列系统研究

将电磁矢量传感器(EVS,electromagnetic vetor sensor)信号处理法与传统MIMO信号处理有机地结合,建立了基于EVS的多天线三维信道模型。采用多重信号分类(MUSIC,multiple signal classification)算法对MIMO的达波信号方向(DOA,direction of arrival)进行空间谱估计,导出基于EVS的三维空间信道解析式,阐明了EVS信号处理与MIMO多径信道相关性的关系。与传统标量传感器阵列(SSA,scalar sensor array)MIMO天线阵列比较,EVS阵列能获取达波信号的多维极化信息,同时具有空间域和极化信号处理能力。因此可缓解空间多径信道相关性,使空间极化分量的相关性趋于零值,而且使MIMO系统性能受空间结构的影响较小。理论分析和仿真结果表明在提高MIMO天线系统性能上,基于EVS阵列的系统比SSA系统具有更高的优越性。     

Accurate DOA estimation using array antenna with arbitrary geometry

The so called universal steering vector (USV) whose locus is equivalent to the array element pattern is applied to the direction of arrival (DOA) estimation by multiple signal classification (MUSIC) algorithm. It is shown that if the USV which includes the effect of the mutual coupling between the array elements is used, the compensation for the received voltage to remove the effect of the mutual coupling is not required any more. The USV for array antennas with arbitrary geometry is derived and evaluated efficiently by using the method of moments (MoM) so that the DOA estimation can be performed accurately by using the array antenna with arbitrary geometry. Numerical examples of the DOA estimation by a dipole array antenna, and an antenna array composed of a monopole antenna and a planar inverted-F antenna (PIFA) mounted on a mobile handset are presented to demonstrate the effectiveness of the proposed method.     

Subspace analysis of spatial time-frequency distribution matrices

Spatial time-frequency distributions (STFDs) have been previously introduced as the natural means to deal with source signals that are localizable in the time-frequency domain. Previous work in the area has not provided the eigenanalysis of STFD matrices, which is key to understanding their role in solving direction finding and blind source separation problems in multisensor array receivers. The aim of this paper is to examine the eigenstructure of the STFD matrices. We develop the analysis and statistical properties of the subspace estimates based on STFDs for frequency modulated (FM) sources. It is shown that improved estimates are achieved by constructing the subspaces from the time-frequency signatures of the signal arrivals rather than from the data covariance matrices, which are commonly used in conventional subspace estimation methods. This improvement is evident in a low signal-to-noise ratio (SNR) environment and in the cases of closely spaced sources. The paper considers the MUSIC technique to demonstrate the advantages of STFDs and uses it as grounds for comparison between time-frequency and conventional subspace estimates     

一种新的时频极大似然DOA估计方法

针对非平稳信号,提出一种新的时频域极大似然DOA估计方法,利用参考阵元与阵列中其它阵元输出之间的互伪Wigner-Ville分布建立起时频域的阵列信号模型,通过时频域极大似然方法获得入射方向估计。与基于空间时频分布矩阵的阵列测向方法相比,该方法具有计算量小、交叉项时频分布利用充分的优点。仿真实验证实了该方法的有效性。     

基于时频点聚类的LFM信号波达方向估计

基于空间时频分布(spatial time-frequency distribution, STFD)的多重信号分类(multiple signal classification, MUSIC)算法常用于非平稳信号波达方向(direction of arrival, DOA)估计, 其关键是选取合适的信号时频点.文中针对传统时频MUSIC算法不能提取各信号时频点且在小角度间隔时估计性能不佳的问题, 以线性调频(line frequency modulation, LFM)信号为研究对象, 提出了基于时频点聚类的DOA估计算法.该算法首先对阵列接收信号进行白化, 利用白化后的接收信号构造STFD矩阵, 达到抑制STFD矩阵的交叉项、突出信号自项的目的, 然后利用K均值聚类提取各信号时频点, 最后运用MUSIC算法估计DOA.对不同角度间隔和不同信噪比时三种算法的估计均方根误差进行了仿真对比, 结果表明:相比经典时频MUSIC算法, 文中算法在小角度间隔和低信噪比时有更好的估计性能.     

Joint parameter estimation of DOD/DOA/polarization for bistatic MIMO radar

In the paper,polarization-sensitive array is exploited at the receiver of multiple input multiple output (MIMO) radar system,a novel method is proposed for joint estimation of direction of departure (DOD),direction of arrival (DOA) and polarization parameters for bistatic MIMO radars. A signal model of polarimetric MIMO radar is developed,and the multi-parameter estimation algorithm for target localization is described by exploiting polarization array processing and the invariance property in both transmitter array and receiver array. By making use of polarization diversity techniques,the proposed method has advantages over traditional localization algorithms for bistatic MIMO radar. Simulations show that the performance of DOD and DOA estimation is greatly enhanced when different states of polarization of echoes is fully utilized. Especially,when two targets are closely spaced and cannot be well separated in spatial domain,the estimation resolution of traditional algorithms will be greatly degraded. While the proposed algorithm can work well and achieve high-resolution identification and accurate localization of multiple targets.     

基于时频分析的雷达信号到达角估计

现有的空间时频分布(STFD)的信号表示只适用于窄带、连续信号的分析，而雷达侦察系统要求对脉冲、线性调频等信号同时进行到达角(DOA)、频率和信号时域参数的估计。本文给出了现有空间时频分布对雷达信号DOA估计的条件，并提出了基于修正STFD矩阵的DOA估计算法。通过对各阵元输出作时频分析，估计信号的频率参数，然后据此构造方向向量和修正STFD矩阵，即可构造MUSIC空间谱。该算法不受基于现有STFD算法的条件限制。     

采用Radon-Wigner变换的二维波达方向估计

针对宽带多线性调频信号2维波达方向(2-D DOA)估计精度低的问题,该文提出了一种基于Radon-Wigner变换(RWT)的2-D DOA估计方法。该方法利用RWT在多目标环境下能够有效抑制交叉项干扰和噪声,具有很好的时频汇聚性特点,通过峰值搜索确定目标个数并重构信号阵列,最后利用MUSIC空间谱分析方法实现了对多个LFM信号的2-D DOA估计。仿真实验表明,基于RWT的DOA估计方法能对非平稳信号进行有效的2-D DOA估计。     

Array processing for nonstationary interference suppression inDS/SS communications using subspace projection techniques

Combined spatial and time-frequency signatures of signal arrivals at a multisensor array are used for nonstationary interference suppression in direct-sequence spread-spectrum (DS/SS) communications. With random PN spreading code and deterministic nonstationary interferers, the use of antenna arrays offers increased DS/SS signal dimensionality relative to the interferers. Interference mitigation through a spatio-temporal subspace projection technique leads to reduced DS/SS signal distortion and improved performance over the case of a single antenna receiver. The angular separation between the interference and desired signals is shown to play a fundamental role in trading off the contribution of the spatial and time-frequency signatures to the interference mitigation process. The expressions of the receiver signal-to-interference-noise ratio (SINR) implementing subspace projections are derived, and numerical results are provided     

MUSIC算法的性能比较

智能天线的核心技术之一是波达方向估计,在无线通信中具有重要作用。MUSIC算法是一种经典的DOA估计算法,但因其计算量大、对于相干及小信噪比信号无法分辨等缺陷,故有较多的改进算法被提出。文中研究了求根MUSIC算法、基于空间平滑技术的MUSIC算法、改进MUSIC算法及修正MUSIC算法。通过仿真分析了角度间隔、信噪比、信号相干对改进MUSIC算法分辨率的影响。以上几种改进MUSIC算法进一步发挥了该算法高分辨率的优势,且有利于其在智能天线方面的应用。     

Spatial evolutionary spectrum for DOA estimation and blind signalseparation

We combine the concepts of evolutionary spectrum and array processing. We present a cross-power stationary periodogram for both direction-of-arrival (DOA) estimation and blind separation of nonstationary signals. We model the nonstationary signals received by each array sensor as a sum of complex sinusoids with time-varying amplitudes. These magnitudes carry information about the DOA that may also be time-varying. We first estimate the time-varying amplitudes using estimators obtained by minimizing the mean-squared error. Then using the estimated time-varying amplitudes, we estimate the evolutionary cross-power distributions of the sensor. Next, using cross-power estimates at time-frequency points interest, we estimate the DOAs using one of the existing methods. If the directions are time varying, we choose time-frequency points around the time of interest to estimate spontaneous source locations. If the sources are stationary, time-frequency points of interest can be combined for the estimation of fixed directions. Whitening and subspace methods used to find the mixing matrix and separate nonstationary signals received by the array. We present examples illustrating the performance of the proposed algorithms     

Reactance domain MUSIC algorithm for electronically steerable parasitic array radiator

Conventional adaptive array antenna processing must observe signals on all of the array antenna elements. However, because the low-cost electronically steerable parasitic array radiator (ESPAR) antenna has only a single-port output, none of the signals on the antenna's parasitic elements can be observed. A direct application of most of the algorithms for the conventional adaptive array antenna is impractical. In this paper, A technique of estimation of direction-of-arrivals (DoAs) is proposed for the ESPAR antenna. This technique is based on the modified MUltiple SIgnal Classification (MUSIC) algorithm. The correlation matrix used in the MUSIC algorithm is estimated from the signal received through the single-port output of the ESPAR antenna as it switches over a set of antenna patterns. Simulation results show that DoAs can be estimated by the reactance domain MUSIC algorithm for ESPAR antennas. Furthermore, the statistical performance on estimation error variance of the reactance domain MUSIC estimator is analyzed and compared with the Crame/spl acute/r-Rao lower bound. Analytic and empirical results show that high-resolution DoAs estimation can be achieved by using the reactance domain MUSIC algorithm for ESPAR antennas.     

一种新型自适应天线的空间谱估计性能分析

利用菲涅尔区相位修正聚焦结构和馈源阵列构成一种新型的多波束自适应天线。本文深入分析了基于该天线的阵列输出特性，与基于均匀线形阵的空间谱估计技术比较的基础上，揭示了其良好的去相关性能。最后应用极大似然估计算法实现了相干信号源在大角度入射的情形下，菲涅尔平板天线对来波方向的有效估计，从而避免了应用MUSIC算法进行来波方向估计时所遇到的观察区域的限制问题。仿真计算的结果表明菲涅尔平板天线良好的空间谱估计性能。     

Dual-polarized array for signal-processing applications in wirelesscommunications

A novel dual-polarized antenna array designed for a spatial division multiple access (SDMA) system working in the 1850-1990-MHz band is designed and built. The antenna is designed to have similar element patterns, and measurements of S-parameters and radiation patterns are presented. The array signal processing performance of the array using all elements and with no compensation for mutual coupling or differences in element patterns is studied through direction-of-arrival (DOA) estimation using total least squares estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT). The results show that the accuracy of the DOA estimates is quite acceptable for wireless communication applications     

基于拉伸式双偶极子天线Q-MUSIC算法的DOA估计

本文指出在四元数模型下,传统双偶极子天线组成的均匀线阵(ULA)在利用四元数多重信号分类算法(Q-MUSIC)估计极化信号波达角(DOA)时,存在“模型相干”问题,并提出了基于实同构矩阵变换的拉伸式双偶极子天线 MUSIC 算法,有效解决了上述问题,所提算法充分利用四元数模型的正交性,性能远优越于基于传统双偶极子天线的 MUSIC 算法,尤其是在低信噪比(SNR)条件下。最后,通过计算机仿真实验验证了所提算法的有效性。     

相干宽带线性调频信号的波达方向估计新方法

提出了一种相干宽带线性调频(LFM)信号的波达方向(DOA)估计新方法。该方法利用LFM信号在分数阶Fourier域上的解线调特性,构造出新的解线调域阵列数据模型,然后结合传统的矩阵重构解相干以及MUSIC算法实现相干LFM信号的DOA估计。若同时存在多组相干LFM信号入射,则首先在不同的能量聚集域上将各信号组分离,然后逐一进行各组内相干信号的DOA估计。该方法充分地挖掘了观测信号所包含的时频信息,增加了可检测的DOA数目,提高了分辨性能和抗噪声性能。此外,该方法无冗余阵元与孔径损失,且适用于任意流型阵列。仿真结果显示,在DOA估计的均方根误差(RMSE)相同时,与传统方法相比,本方法可获得8dB左右的信噪比增益。     

基于TD-SCDMA无线定位虚拟线阵四阶累量修正MUSIC算法的研究

无线定位的圆-角定位技术中,DOA估计极其重要。本文针对基于TD-SCDMA智能天线预处理后的虚拟均匀线阵MUSIC算法带来的阵列孔径小,抗阵元误差扰动性差的不足,研究了基于模式空间虚拟均匀线阵四阶累量的MUSIC算法,由于虚拟线阵四阶累量MUSIC算法的应用范围局限于独立的信号源的DOA估计,不能用于相关信号源DOA估计,因而提出了基于模式空间虚拟均匀线阵四阶累量的修正MUSIC(FOC-MMUSIC)算法,有效地拓展了阵元孔径,改善了系统抗阵元误差扰动和算法对相关信号源DOA的估计性能。     

基于线性时频分析的非平稳源空间谱估计

针对存在幅度和相位调制的非平稳信号的定向问题,本文提出了一种改进的线性时频空间谱估计算法。该算法首先在线性时频面上检测信号的时频脊,并沿各时频脊进行采样形成独立的阵列时频快拍,然后对各快拍采用通用算法进行空间谱估计,此时阵列能估计的信号源数已不再受阵元数的限制。计算机仿真实验表明,该算法具有优良的定向精度,且能有效地对多个非平稳信号源进行分离和空间谱估计,其计算量远低于二次时频空间谱估计算法。     

多径传播条件下宽带线性调频信号波达方向估计方法

针对信号出现多径传播情况时现有宽带信号波达方向（direction of arrival, DOA）估计方法性能下降的问题,提出了一种多径传播条件下宽带线性调频（chirp）信号波达方向估计方法,该方法将导向有效投影（steered effective projection, STEP）技术与宽带线性调频信号的时频特性相结合,对具有不同时频特性的信号分量进行分离,逐个处理,并以时频分布矩阵代替传统的协方差矩阵,从而构造有效噪声子空间,实现时域角度估计。本方法无需进行信号聚焦操作,因此理论上不受聚焦误差的影响。仿真结果验证了所提方法的有效性。