盲波束形成算法及其C语言实现

阵列信号处理作为信号处理的一个重要分支，在通信，雷达，声呐，地震勘探，射电天文等领域获得了广泛应用和迅速发展。波束形成技术是阵列信号处理中的一个主要问题，它使阵列方向图的主瓣指向所需的方向，盲波束形成算法，可以在不知道阵列流形，信号和干扰方位的情况下，仅根据各个阵元的观测数据，恢复出信号．本文主要讨论应用VC 语言实现和比较了几种基于累积量的盲波束形成算法的性能。     

基于共轭虚拟阵列的稳健波束形成方法

针对提高阵列天线波束性能问题,本文提出了基于共轭虚拟阵列的信号导向矢量扩展方法.利用共轭虚拟阵元扩展阵列,增大了阵列孔径却不改变实际阵元数,降低了副瓣电平并且不会增加天线制造成本.在虚拟阵列的基础上对信号导向矢量进行扩展,使阵列波束形成效果更加稳健.本文通过在有无干扰以及存在幅度和相位误差情况下对11个阵元阵列天线进行...     

基于频域分解的水声信号宽带盲波束形成

盲波束形成算法可以在不知道阵的流型、信号及干扰方位的情况下,仅根据各阵元接收的数据恢复信号。由于水声信号为宽带信号,为了充分利用宽带信息,提出利用频域分解的方法获得满足窄带条件的信号,并利用窄带盲波束形成JADE（Joint Approximate Diagonalisation of Eigen-matrices）算法进行处理。对宽带盲波束形成算法进行了理论推导和仿真实验。研究结果表明,盲波束形成算法相对于常规波束形成在信号恢复方面有优越性。     

阵元失效对克罗内克积波束形成性能的影响

对于一类规则阵型,可以引入克罗内克积提高最小方差无失真响应波束形成器的鲁棒性,同时降低其运算复杂度;然而,对于阵元数较多的规则阵列,阵元失效的可能性大幅增加,当某些阵元失效时,规则阵列不满足克罗内克分解。针对常见阵元失效问题,文章研究了阵元失效的三种情况对最小方差无失真响应波束形成器与克罗内克积自适应波束形成的性能影响。仿真与实验结果证明,信号完全缺失的通道对自适应波束形成器的影响最大,信号重复的通道对自适应波束形成器的影响最小。文章据此提出了一种低复杂度的信号恢复方法,通过使用相邻通道的信号代替信号缺失通道,提升阵元失效情况下的波束形成性能。     

稳健的波束优化设计及FPGA实现

在分析二阶锥规划(Second-Order Cone Programming,SOCP)算法的基础上,设计了声呐阵列并采用SOCP方法对其波束图进行了优化;根据SOCP的波束优化设计方法,设计了基于FPGA的16元均匀圆阵的波束形成器。目的在于提高波束优化设计的稳健性以及信号处理系统的运算实时性、运算精度等。对FPGA波束形成器的仿真性能进行了分析,主要分析了以下两个方面:首先分析了当权值位数不同时对波束形成器输出的影响,其次分析了波束优化设计方法的抗阵列流形误差的性能。仿真设计结果和实验表明本文方法的有效性。二阶锥波束优化设计的波束图有着良好的稳健性,采用12位权值的FPGA波束形成器,抗阵元位置误差性能也比较好。     

基于多普勒特征恢复的声矢量阵鲁棒自适应波束形成方法

在短快拍、信号导向矢量失配环境下,传统的自适应波束形成方法性能受到影响,对角加载技术是提高算法在复杂环境下性能鲁棒性的重要技术之一。针对水声环境和水声信号特点,提出一种基于声矢量阵的自适应波束形成方法。该方法利用水声信号的多普勒频率信息,在不同环境下自适应地选择最优对角加载因子,确定波束形成的权矢量,从而实现提取期望目标信号、抑制干扰和噪声的目的。无需任何用户参数,鲁棒性强、估计精度高。最后基于声矢量阵进行仿真实验,仿真结果证明了所提出的方法能够有效地获取目标信号,具有较好的抗干扰能力。     

自适应Notch滤波器在阵列信号处理中的应用

为了不增大阵列尺度采用信号处理方法得到高分辨率的波束指向性,首先利用Notch滤波器的＂离线重构＂实现窄带波束形成,进而结合其瞬时相位估计方法,研究了基于自适应Notch滤波器的恒定束宽波束形成技术,利用信号处理方法将矢量传感器阵列接收的低频窄带信号转化为具有指向性的较高频率波束,并采用虚拟阵元技术消除波束栅瓣的影响,给出了实际应用中具体的信号处理方法。仿真和湖试验证表明这种基于自适应Notch滤波器的恒定束宽波束形成方法是合理可行的。最后,针对适应实时信号处理的要求提出将这种方法与目标自动跟踪系统相结合的改进方向。     

基于反卷积的双线阵聚焦波束形成被动定位方法

为了提高双线阵聚焦波束形成在阵元数少或频率低时的定位精度,文章研究了一种基于反卷积的双线阵聚焦波束形成被动定位方法。首先在测量区内对双线阵接收信号进行球面波补偿,给出噪声源分布的声图信息。然后根据阵型的参数,计算双线阵的指向性函数。最后利用一种适用于移变阵列的二维扩展R-L反卷积算法,对声图波束输出和双线阵的指向性函数做反卷积,求解基于反卷积波束形成的源的分布。该方法旁瓣更低,分辨力更高,有效提高双线阵聚焦波束形成的定位精度和左右舷分辨能力,为后续的减振降噪、噪声检测等工作提供了参考。     

空域预滤波的稳健自适应波束形成方法

假定的期望信号方向向量与真实信号方向向量存在误差时,常规自适应波束形成性能将严重降低,针对该问题,提出了一种稳健的自适应波束形成算法.首先利用凹槽空域矩阵滤波器对基阵接收数据进行空域预滤波,消除协方差矩阵中的期望信号分量,然后重构协方差矩阵同时反变换到阵元域,再用重构的协方差矩阵形成自适应波束权向量.由于方法消除了期望信号分量的影响,极大地提高了自适应波束形成算法对系统误差的稳健性.计算机仿真验证了所提方法的有效性.     

聚焦波束形成声图法误差分析

聚集波束形成声图测量方法可以实现近场目标的被动定位．利用该方法接收数据或进行数据处理的过程中必定会有各种误差产生,本文从聚焦峰尺度、阵元偏差、波长等方面对聚焦波束形成声图测量方法的影响进行了分析,经仿真研究与实验数据分析可以得出聚焦波束形成声图法受距离与波长的影响较大,但对于阵元的位置要求不高,利用该方法可以实现近程目标的高精度定位。     

Eigenspace-based blind pattern optimisations of steerable antenna array for interference cancellation

A novel adaptive algorithm for an array using directional elements called a hybrid smart antenna system is proposed. The algorithm controls the element patterns on the basis of an objective function composed of eigenvalues of a covariance matrix. A high and stable array output signal-to-interference-plus-noise ratio is achieved by improving both the received powers and the spatial correlation coefficient between incident waves, without prior knowledge such as directions-of-arrival, channel state information or training signals. The characteristics of the proposed algorithm are theoretically and numerically clarified for a simple case involving two incident waves. Convergence with least mean squares algorithm is found to be as fast as that with recursive least squares algorithm in this system. Also, simulation for statistical performance evaluation is carried out in comparison with a conventional system. Furthermore, a method to implement the proposed eigenspace control algorithm without having to solve the eigenvalue problem is shown.     

Compact Interlaced Dual Circularly Polarized Sequentially Rotated Dielectric-Resonator Antenna Array

In this study, a compact 2 × 2 interlaced sequentially rotated dual-polarized dielectric-resonator antenna array is proposed for 5.8 GHz applications. The array is composed of a novel unit elements that are made of rectangular dielectric resonator (RDR) coupled to an eye slot for generating the orthogonal modes, and to acquire circular polarization (CP) radiation. For the purpose of miniaturization and achieving dual polarized resonance, the array is fed by two interlaced ports and each port excites two radiating elements. The first port feeds horizontal elements to obtain left hand circular polarization (LHCP). The second port feeds vertical elements to obtain right hand circular polarization (RHCP). A quarter-wave length transformer is employed to reduce the attenuation and consequently increase the array gain performance. The 35 × 35 mm² () gains were 8.4 and 8.2 dBi for port 1 and port 2, respectively, with port isolations of −33.51 dB. The design achieves a voltage standing-wave ratio (VSWR) < −10 dB and an axial ratio (AR) ˂ − 3 dB bandwidth of 2.48% (5.766 to 5.911 GHz) for LHCP at port 1 and a VSWR < −10 dB and AR ˂ −3 dB bandwidth of 2.28% (5.788 to 5.922 GHz) for RHCP at port 2. The findings of the proposed design validate its use for ISM band applications.     

混凝土结构健康检测的声发射圆阵波束形成仿真分析

采用了声发射(Acoustic Emission,AE)均匀圆阵并分析其波束形成特性,通过仿真分析了阵元数目及声发射模拟信号频率的变化对波束模式的影响.结果表明,当频率不变,阵元数目为4~32时,随着阵元数目的增加,角分辨率保持不变,最高旁瓣降低,可达-8 dB左右.混凝土结构内部缺陷声发射信号的超声频段一般在25~200 kHz,当阵元数目不变时,随着频率的升高,角分辨率随之升高,最高旁瓣也随之增大.另外,文中提出如何设计一个性能相对稳定的阵列,并通过从噪声信号中提取有用信号的实例说明声发射均匀圆阵空间匹配滤波性能.     

Omni-directional guided wave transducer arrays for the rapid inspection of large areas of plate structures

Omni-directional guided wave array transducers contain a circular pattern of elements that individually behave as omni-directional point transmitters or receivers. The data set acquired from such an array contains time-domain signals from each permutation of transmitter and receiver. A phased addition algorithm is developed that allows an omni-directional, B-scan image of the surrounding plate to be synthesized from any geometry of array. Numerically simulated data from a single reflector is used to test the performance of the algorithm. The results from an array containing a fully populated circular area of elements (Type I array) are found to be good, but those from an array containing a single ring of elements (Type II array) contain many large side-lobes. An enhancement to the basic phased addition algorithm is presented that uses deconvolution to suppress these side-lobes. The deconvolution algorithm enables a Type II array to equal the performance of a Type I array of the same overall diameter. The effect of diameter on angular resolution is investigated. Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the S/sub 0/ Lamb wave mode in a 5-mm thick aluminium plate are processed with both algorithms and the results are discussed.     

Experimental investigation of directional characteristics for ionospheric clutter in HF surface wave radar

The unwanted radar echoes from the ionosphere are collectively called ionospheric clutter. It has proved to be the greatest impediment to achieve consistently good performance in long-range detection of surface vessels and sea-state monitoring for high-frequency surface wave radar (HFSWR). Field experimental data recorded by the HFSWR OSMAR2003 (Ocean State Monitor and Analysis Radar, manufactured in 2003) has been used in detailed investigations of the directional characteristics for this ionosphere clutter, leading to the development of effective mitigation techniques based on antenna design and adaptive signal processing. Particular attention is given to the amplitude and phase relationship among multiple spatial channels for two types of ionospheric clutter. Preliminary experimental results show that the random gain and phase variation of the antenna pattern overhead null destroyed the amplitude and phase consistency among channels. As a result, no significant measured directivity is observed in this type of specular clutter. For the incidence clutter from a lower elevation angle, it is observed that the spread clutter possesses high directivity. A nonlinear receiving array composed of multiple V-shaped antennas without deep and broad null at near-vertical incidence is proposed for adaptive ionospheric clutter suppression     

一种声场空间特性测量系统的性能研究

室内声学测量中,在声源重复发射声信号的同时,将单个无指向性传声器缓慢而匀速地转动,其测量结果等效于以转盘转轴为中心的圆形传声器阵列,相应的测量系统简称为RRS。通过消声室测量,着重分析此测量系统在方向脉冲响应测量中的性能及主要影响因素：结果表明,在满足传声器旋转半径大于1／4信号波长的条件下,系统可具有令人满意的方向分辨能力。     

Computationally efficient sound field calculations for a circular array transducer

A computationally efficient method is presented for calculating field pressure distributions from a circular phased array transducer. This method employs a form of the rectangular radiator approach modified for use with the geometry of a circular array. The curved surface of the elements, radiating either continuous wave or pulsed excitation signals, is divided into incremental rectangular areas small enough so that the Fraunhofer approximation can be applied. Once the directivity of a single element is found, the array beam pattern can be calculated using superposition and suitable coordinate transformations. The validity of this approach is verified through comparisons with experimental data from a circular phased array. The results show that the location and amplitude of the grating lobes and main lobe width can be predicted with reasonable accuracy by using this method.     

一种具有多重稳健性的自适应波束形成算法

由于存在阵元幅相差、期望信号导向矢量误差和数据失配等问题,传统的自适应波束形成算法性能下降,针对这一问题,提出了一种新的对于上述多种误差同时具有稳健性的波束形成算法。该算法以最小二乘恒模算法为基础,结合最优对角加载和协方差矩阵锥消技术,使得算法适用于同时存在多种误差的情况。结果表明,与目前已有的同类算法相比,该算法克服了期望信号信噪比大时算法性能恶化的缺点,具有更好的输出信干噪比,并且通过计算机仿真验证了它的有效性和优越性。     

Biologically inspired structural diagnostics through beamforming with phased transducer arrays

This paper discusses research in the use of biologically inspired spatial phased transducer arrays for the nondestructive evaluation of homogeneous and heterogeneous structural components. It is shown that beamforming, which is used by orb web spiders to locate their prey in a network of web fibers, can be achieved by applying weights and time delays to the tapped signals from a transducer array in a narrow frequency band to obtain desired directional sensitivities and optimal array gains. The resulting spatio-temporal filters are then used to detect, locate and quantify structural damage. The theory of beamsteering and beamforming for processing propagating wave data in damaged elastic media is discussed. Experimental results for homogeneous and heterogeneous plates are given to verify the theoretical discussions. Design considerations for the phased arrays are examined as are the benefits of nonlinear array geometries for better spatial coverage. The advantage of using adaptive over conventional beamforming is demonstrated with a Frost Constraint adaptive technique.     

模拟退火算法设计阵元缺失基阵方向图的方法

基阵方向图设计是声纳设计中的核心和重要部分,由于声纳系统的使用环境比较复杂,为了快速、有效地在阵元缺失的情况下对基阵方向图进行设计,引入了模拟退火算法对这类问题进行处理。模拟退火算法是近年来出现的全局优化算法,易于编程、有良好的收敛性。计算机仿真结果表明,模拟退火算法可以很好地完成在阵元缺失情况下对基阵方向图的补偿设计。