超增益低频接收基阵仿真研究

研究一种具有超增益性能的单向水听器作阵元的基阵的性能.为改善海水中信号的精度和分辨率,对小尺度阵列稳健的波束形成方法进行了研究.采用不同的算法,求出相应的权矢量,从而得出不同条件下的波束图及阵增益.通过比较优选出所需的权矢量,完成波束形成器的设计.通过仿真比较了四种不同的波束形成算法,分别得出不同信噪比条件下小型化线列阵的波束图.通过对基阵的波束图、增益及稳健性等特性的研究,分析比较了几种波束形成方法的优缺点.仿真结果表明,改进的白噪声增益约束法既可获得高的增益,又具有好的稳健性.     

一种小型矢量阵优化波束方法研究

在小型声纳平台中由于单个矢量水听器所含的振速传感器具有自然指向性,其组成的矢量阵较传统水听器阵有优越性,但单个矢量水听器的自然指向性波束较宽,组成的矢量阵的-3dB束宽和旁瓣级不够理想。该文利用单个矢量传感器的声压、振速信息联合处理形成较好指向性,并用于矢量阵获得良好的阵列效果,同时分析了该方法对线阵和圆阵的影响。仿真结果表明当线阵的阵元间距和圆阵半径都为0．5米时,矢量阵接收低频信号所形成的波束图中-3dB束宽在以25°内,第一旁瓣级低于-60dB,这证明了该文的方法是有效的。     

矢量水听器阵波束域MUSIC算法研究

矢量水听器可同时拾取声压和振速信息,成阵后水听器间的相移信息量增大。基于矢量水听器阵的波束形成性能明显由于同条件下的声压水听器阵,但其空间分辨力依然受阵列物理空间的限制。已经有人研究了矢量水听器阵的高分辨谱估计方法（MUSIC算法）,但属于对阵元域信号进行的直接处理,运算量较大。提出一种基于矢量水听器阵的波束域MUSIC算法（BMUSIC）。该算法首先将矢量水听器阵元的空间数据转换到波束空间,然后对转换后的数据再运用MUSIC算法。不但实现了降维处理,减小了运算量,而且可进一步抑制扫描扇面外的噪声。对BMUSIC算法进行了仿真并与常规MUSIC算法进行了比较。结果表明,该方法可得到与阵元域MUSIC算法相当的方位分辨力。     

矢量阵信号子空间投影波束形成

针对常规波束形成无法充分发挥矢量阵抗干扰性能的问题,提出了基于信号子空间投影的波束形成方法.对声矢量阵接收信号进行三阶张量建模,利用高阶奇异值分解得到信号子空间,并将阵列流形矢量投影于其上,从而得到相应的空间谱计算方法.计算机仿真试验验证了该方法的有效性.     

矢量阵一种简单的相位误差校正方法

分析了矢量水听器阵的阵列流型和误差模型,针对矢量水听器阵列声压和振速通道存在相位误差问题,应用常规波束形成方法和MUSIC方法进行方位估计误差大。并对通道存在估计性能下降的问题,提出了一种简单的相位误差校正方法。利用阵列流型向量在信号子空间的投影,得出存在相位误差的阵列流型向量就是信号子空间的特征值为＂一＂的特征向量,通过与精确的阵列流型向量比较求出矢量阵的相位误差。最后,修正矢量阵的相位误差,得到准确的方位估计能力。通过计算机仿真,验证了算法的可行性和准确性。     

小孔径圆环阵凹槽超增益波束形成技术研究

在水下目标声纳检测问题的研究中,为了抑制水下噪声信号,提出了小孔径圆环阵凹槽超增益波束形成方法.上述方法针对均匀圆环阵,在保证基阵输出增益最大的前提下,采用凹槽波束优化方法,设计具有抑制特定方向波束响应输出的波束,以抑制该方向强的强干扰对目标方位估计的影响.仿真结果表明,改进方法能有效抑制期望信号方向以外的干扰对目标方位估计的影响;干扰信号越强,波束图输出谱凹槽越深;在小孔径圆环阵的基础上能实现对水下目标低频辐射噪声信号有效检测和方位估计.     

基于矢量水听器的非均匀阵列APES波束形成算法

针对传统幅度与相位估计（Amplitude and phase estimation,APES）算法难以应用于非均匀阵列的问题,研究了基于矢量水听器的APES算法。利用矢量水听器能够同时共点测量声压和质点振速的特点,将矢量水听器的声压和解析振速通道作为两个子阵,两路子阵之间只存在一个相位差,且与阵元位置无关,使得APES算法能够应用于任意形状的阵列。推导和分析了矢量APES算法的阵增益及其稳健性。分析和 仿真表明：该方法相比于传统APES算法,具有更高的阵增益,且能适用于非均匀阵列;相比 于最小方差无失真响应（Minimum variance distortionless response,MVDR）算法,具有更好的稳健性,能解决相干问题及能够获得更准确的信号功率,并用实测数据验证了算法的 有效性。     

鱼雷声纳自噪声及环境噪声仿真及其应用

环境噪声与航行噪声通过其强度对自噪声级的影响与方向性对基阵阵增益的影响，降低了鱼雷自导分辨率并增大估计误差，对鱼雷自导工作性能有着严重的影响。该文通过对鱼雷自导航行自噪声与环境噪声的仿真与试验研究，对半实物仿真航行自噪声与环境噪声的方案进行了论证与分析，讨论了各向同性噪声场与非各向同性噪声场的空间相关性与仿真生成的方法，并对基阵波束相关性进行了相应的分析。     

基于一体化结构的声自导发射/接收波束形成

根据鱼雷电子系统发展的需求,提出了基于交换式以太网的鱼雷电子系统一体化结构.在一体化结构的框架下,将声自导发射波束形成和基阵接收波束形成作为功能独立的智能化执行器和传感器.在声自导发射波束形成模块,采用DDS方法生成基准信号,并通过延时滤波算法精确控制通道间的相位关系,从而控制声自导发射波束的指向.在基阵接收波束形成模块中,提出了"二次正交采样"的方法,实现高频窄带阵列信号的实时处理,并在复包络的基础上完成接收波束形成.最后,验证了发射波束形成和接收波束形成的正确性.     

圆形基阵指向性的仿真研究

对一种适用于小型水下航行器的圆形基阵进行了研究.通过建立数学模型,对其指向特性进行了仿真,分析了影响基阵指向特性的各个因素.结果表明,与一般阵元相比,采用具有单向性与超指向性的水听器作阵元,不仪可以消除基阵的栅瓣、降低旁瓣、减小波束(主瓣)宽度,并能大大提高指向性指数,从而全面地改善基阵的指向特性;而且随着频率的降低,改善效果更为显著.采用单向性水听器作阵无的基阵在低频条件下工作更能显示其优越性.     

基于子带SDL的LCMV宽带波束形成性能分析

对子带阵元延迟线 （SDL）波束形成器的线性约束最小方差（LCMV）宽带自适应波束形成算法进行了性能分析 。推导了子带LCMV算法的输出信干噪比（SINR）的解析表达式,对比了子带LCMV算法和全带 LCMV算法的阵列响应性能,以及阵元数量、输入信噪比（SNR）和阵元间距对输出SINR的影 响,并分析了子带滤波器组的参数对子带LCMV输出SINR性能的影响。仿真结果表明子带LCMV 算法可有效提高性能,并可在不降低性能的条件下降低阵元需求。     

Blind Acoustic Beamforming Based on Generalized Eigenvalue Decomposition

Maximizing the output signal-to-noise ratio (SNR) of a sensor array in the presence of spatially colored noise leads to a generalized eigenvalue problem. While this approach has extensively been employed in narrowband (antenna) array beamforming, it is typically not used for broadband (microphone) array beamforming due to the uncontrolled amount of speech distortion introduced by a narrowband SNR criterion. In this paper, we show how the distortion of the desired signal can be controlled by a single-channel post-filter, resulting in a performance comparable to the generalized minimum variance distortionless response beamformer, where arbitrary transfer functions relate the source and the microphones. Results are given both for directional and diffuse noise. A novel gradient ascent adaptation algorithm is presented, and its good convergence properties are experimentally revealed by comparison with alternatives from the literature. A key feature of the proposed beamformer is that it operates blindly, i.e., it neither requires knowledge about the array geometry nor an explicit estimation of the transfer functions from source to sensors or the direction-of-arrival.     

Constrained minimum power combination for broadband beamformer design in the STFT domain

Beamforming using sensor array is widely used in spatial signal processing since it offers better spatial focusing capability than single sensor. However, in practical applications for broadband signal, there always exists a trade-off issue between the directivity capability of an array and its robustness on system errors. In this paper, in order to combine merits of different beamformers instead of trade-off their performances, we propose a constrained minimum-power combination method. We firstly analyze two optimal beamformers that maximize Directivity Factor (DF) and White Noise Gain (WNG) respectively. Then we propose a non-linear combination method, which automatically selects the best beamformer that has the minimum output power, so as to control the unwanted white noise amplification and keep the maximum DF if possible. Two solutions to the proposed combination strategy are given. They do not need to determine the correct trade-off factor used in linear combination method, and avoid challenge estimations on noise and target statistics required in adaptive beamforming. The performance of the proposed beamformer is evaluated in ideal noise fields and complicated noise fields respectively. It is shown that the proposed beamformer integrates merits of different beamformers. It always achieves the best speech quality and biggest noise reduction compared to other popular beamformers.     

半球面共形阵列波束综合技术研究

针对天线的抗干扰提高信噪比问题,球面阵列天线的增益在不同方向灵活可变的优点,但球面阵列天线是非线性的,没有解析解,传统的线性波束综合方法很难解决球面阵列天线复杂多约束的增益问题。为解决上述问题,使用了零陷技术。现有的方法着重干扰方向已知情况下的零陷形成技术,而对干扰方向未知多变的情况研究很少,采用改进的遗传算法用于复杂的宽角零陷形成,可以解决干扰方向未知情况下的零陷形成难题。     

基于单矢量传感器的强干扰噪声抑制方法

通过对单矢量传感器各通道输出不同形式的组合可以抑制干扰噪声,但高次乘方和最小均方误差准则2种方法包含非线性运算,使目标信号产生失真;常用的线性运算方法只能完全抑制与目标方位相差一固定值的干扰信号。对单矢量传感器各通道授予不同的权重系数并进行线性运算,根据最小噪声功率输出准则,在不降低目标信号信噪比的同时,通过调节权重系数,可抑制各向同性噪声场中任一方位的强干扰信号。仿真显示:本方法可在不降低目标信号信噪比和保证目标信号不失真的前提下,完全抑制与目标方位相差70°～290°范围内任一方位的强干扰噪声。     

Front-end processor using BBD distributed delay-sum architecture for micromachined ultrasonic sensor array

Micromachined technology makes it possible to integrate the ultrasonic sensor with the front-end processing circuit together, and make an ultrasonic system smart, compact and low cost. An ultrasonic sensor array with resonant frequency of about 60 kHz is fabricated for airborne applications, using sol-gel derived Pb(Zr,Ti)O/sub 3/ thin film and Si-based micromachining technique. The distributed delay-sum architecture based on a bucket brigade device (BBD) is employed for the beamforming of the sensor array in order to reduce chip area, simplify system design, improve power efficient and achieve monolithic integration. A charge attenuator is proposed to increase the dynamic range of the input signal and overcome the charge overflowing in bucket capacitors. A charge amplifier based preamplifier is used to interface the sensor array and beamformer. A prototype front-end processor shows good SNR with the dynamic range larger than 50 dB, and a beamforming performance consistent to the theoretical calculation very well.     

一种近场麦克风阵列后滤波语音增强方法

介绍了一种用于近场麦克风阵列后滤波语音增强的方法,避免了现有的利用自功率谱密度和互功率谱密度的Zelinski和McCowan后滤波器中噪声功率谱过估计的问题,并加入了近场传播的幅度衰减补偿和相位延迟补偿。使用卡内基梅隆大学提供的多麦克风语音数据以及使用Habets E A P提出的生成阵列散射噪声的方法进行的仿真实验,证明了改进的方法在语音质量客观评估量方面优于Zelinski后滤波法和McCowan后滤波法。     

基于小波旁瓣相消器的轴承故障特征提取

为解决强背景噪声下声信号提取的轴承故障特征不显著问题,提出一种基于小波旁瓣相消器的故障特征提取方法。该方法利用小波滤波器组将含噪故障轴承声信号变换到小波域,进行小波域阵列广义旁瓣相消自适应波束形成,再通过小波滤波器组重构增强后的故障轴承信号,最后对重构增强后的信号进行包络解调并提取故障特征频率进行故障诊断。实验结果表明,该方法能够在强背景噪声下有效提取滚动轴承故障特征,并且相较于传统的延时求和波束形成器具有更好的降噪和故障特征增强效果。     

On the stability of some high-resolution beamforming methods

Orthogonal beamforming is the name of certain high-resolution methods for estimating the spectra of a wave field received by an array of sensors. The methods use the eigenvalues and eigenvectors of the spectral matrix of the sensor outputs. The problem is to predict the behavior of such methods when only an estimate of the matrix is known. The sensor outputs may consist of sensor noise, ambient noise and noise from a finite set of discrete sources. The properties of the eigensystem of the spectral matrix in the case of weak ambient noise motivate the methods of orthogonal beamforming, for example Pisarenko's nonlinear peak estimates and the projection estimates of Owsley. If the spectral matrix is estimated by one of the classical methods, some asymptotic distributional properties of the matrix estimate and its eigensystem are well known. They can be used to determine asymptotic expressions, e.g. for the first and second moments of the peak estimators and to approximate the distributions. The parameters, however, cannot be calculated in applications, since the eigensystem of the exact spectral matrix is required. Therefore, we have developed bounds for the deviation of the peak estimates which only use weak knowledge about the matrix. We have applied some results on perturbations of hermitian operators. The asymptotic behavior of the bounds for the projection estimator is investigated and possibilities for their estimation are indicated. Finally, we report on extensive simulations with random matrices to evaluate the new bounds. As a result, we have found that the projection estimator behaves stably and there are tight bounds if the eigenvalues of interest are sufficiently separated from the rest.     

基于波束形成与多参考源噪声对消的语音增强算法

通过传声器阵列采用波束形成技术采集语音信号,同时使用参考传声器获得背景噪声信号,本文提出一种基于波束形成和自适应多参考噪声对消的语音增强算法。该算法不依赖任何信号模型且无需对噪声信号的统计特性进行先验假设,可以适应背景噪声的突然改变,同时具有良好的实时性和鲁棒性。可广泛应用于复杂噪声环境下目标语音识别,仿真结果表明了该算法的有效性。