基于波束域MUSIC方法的高分辨方位估计

现代声纳系统普遍采用水听器基阵和一定的信号处理来提高对目标的检测和定位能力，而基阵的波束形成则在其中起着核心作用。文中研究了窄带波束域高分辨方位估计技术，分析了波束域MUSIC方位估计的构造过程和具体实现方法。仿真计算表明，基于波束域MUSIC的方位估计算法是一种分辨空间小角域内多个目标的有效方法。     

基于宽带稳健STMV波束形成的相关检测方法

采用一种宽带相关结合稳健自适应波束形成的检测方法,来提高弱目标在强干扰背景下的检测能力。宽带相关检测具有多目标方位分辨力高的优点,它基于常规波束形成得到,但由于其旁瓣级有限,存在强干扰时会导致其旁瓣区域的相关检测产生凹陷,因此直接影响弱目标的检测能力。通过分析常规宽带相关检测中目标旁瓣区域产生凹陷原因,利用宽带稳健自适应波束形成的干扰抑制能力,提出了一种将宽带稳健导向最小方差波（Steered Minimum Variance,STMV）与宽带相关检测结合的宽带检测新方法。该方法能有效消除相关检测中强干扰的影响,提高被动声呐的宽带检测性能。仿真和试验数据处理结果验证了该方法的有效性。     

可利用波束输出信息的高分辨方位估计算法

本文介绍一类可以利用波束输出信息实现高分辨方位估计的算法,这类算法由于所利用的波束输出比阵元个数少得多,计算量得以降低,计算机仿真结果表明,对常见声纳接收阵波束输出信息进行高分辨方位估计不仅是可行的,而且还可获得比常规阵元域高分辨算法更低的分辨信噪比门限。     

一种新的稳健CAB盲波束形成算法

通过限制估计的方向向量与真实的方向向量之间的误差范数的边界,提出了一种新的稳健CAB（周期自适应波束形成）盲自适应波束形成算法。该算法克服了方向向量失配引起的自适应波束形成器的性能劣化问题。计算机仿真试验表明,较采用传统对角加载技术的R-CAB盲波束形成算法和WCPO-CAB算法而言,该算法进一步提高了稳健性和输出信干噪比。     

矢量传感器线列阵波束域MUSIC方位估计

在研究矢量传感器阵列目标估计基础上,本文首次在矢量传感器阵列处理领域将矢量阵波束形成与波束域目标估计算法结合起来,实现了高精度目标方位估计,与常规阵元域和波束域方法相比,提高了多目标估计性能,增大了阵列输出增益,大大减小了计算量.仿真验证了本算法的优越性.     

基于稳健Capon波束形成的阵形校正

由于受地形、海流和布放方法等的影响,声阵在布放后通常会偏离原定阵形。若直接利用原定阵形作方位估计,则各种高分辨方位估计算法的性能通常会退化甚至失效。因此,为了在实际中应用这些算法,必须对阵元的位置进行校正。RCB(Robust Capon Beamforming)是最近提出的一种稳健自适应波束形成算法,该算法直接对导向矢量进行估计,并用估计的导向矢量作波束形成,从而有效避免了因阵列流形失配而导致的算法性能下降。借用RCB的思想,提出一种新的阵形校正方法,该方法对导向矢量进行估计,然后用估计的导向矢量推导出阵元的位置。湖试结果表明了该校正方法的有效性。     

一种旁瓣级可控的MVDR波束形成算法

针对传统的最小方差无畸变响应（Minimum Variance Distortionless Response,MVDR）波束形成方法存在的旁瓣较高且抑制干扰性能不稳健的情况,提出一种旁瓣级可控的自适应波束形成算法。该算法在MVDR基础上进行峰值搜索,将获得的峰值点从大到小进行排序,取次大值作为最高旁瓣的值,将得到的最高旁瓣值与期望旁瓣值比较,在其方位添加虚拟干扰加以抑制,从而得到新的波束图。再对新的波束图进行峰值搜索,不断重复上述过程,经过有限次迭代以达到期望旁瓣值。计算机仿真结果表明在均匀线阵基础上该算法能够将旁瓣控制到期望旁瓣级以下且比较稳健。     

基于高阶次Cross Sensor处理的波束形成方法

为得到鲁棒性、高分辨波束形成,提出了一种高阶次Cross Sensor处理方法。该方法依据阵元间协方差矩阵同一斜对角线上不同元素具有相同相位差的特点,对协方差矩阵进行M阶次Cross Sensor处理后可虚拟出近(2~M-1)(N-1)个虚拟阵元(N为原始阵元数)。虚拟阵元的增加可扩大线阵有效孔径,降低波束形成主瓣宽度,提高方位分辨率。在Cross Sensor处理过程中,该方法对协方差矩阵同一斜对角线上不同元素进行了叠加运算,可进一步削弱噪声对波束形成的影响,提高了波束形成鲁棒性。数值仿真和海上试验结果表明,该方法既能有效降低波束形成主瓣宽度,提高方位分辨率,又可削弱方位历程图干扰背景。相比已有的逆波束形成,该方法具有较好的方位分辨率;相比已有的基于AR模型的高分辨逆波束形成,该方法对最低门限信噪比的要求较低,方位估计均方误差较小。     

一种新的被动水声探测盲自适应波束形成器

提出了一种适合拖曳线列阵鱼雷自导系统的新的被动水声探测盲自适应波束形成器。介绍了该方法的设计思路和推导原理,然后通过计算机仿真验证了该方法的收敛性,并在不同信噪比、快拍数条件下与单独使用自适应MVDR波束形成器在角度估计方面做了对比。与单独使用盲源分离算法在源信号估计方面作了比较。最后证明该方法是一种稳健的、对信噪比变化不敏感的适合被动水声探测的新方法。     

MVDR自适应波束形成技术在水声中的研究进展

高分辨波束形成器比常规波束形成具有更好的方位分辨力与干扰抑制能力。该波束形成器能够提高阵列输出信干噪比,从而提高声呐的探测性能。与多重信号分类、旋转不变子空间等方法相比,最小方差无畸变响应(Minimum Variance Distortionless Response,MVDR)波束形成器输出真实反映了观察方向的信号功率,同时可提供波束时间序列做后置处理,在水声阵列处理领域得到了快速发展和深入研究。对高分辨MVDR技术在水声阵列处理中的研究进展进行了回顾,重点介绍了其宽带处理、稳健性、运动补偿、解相干等国内外的研究热点和最新成果,同时给出其在各种水声阵列处理领域的应用前景。     

Beamspace adaptive beamforming for ultrasound imaging

Applying the Capon adaptive beamformer in medical ultrasound imaging results in enhanced resolution by improving the interference-suppressing capabilities of the array. This improvement comes at the expense of an increased computational complexity. We have investigated the application of a beamspace adaptive beamformer for medical ultrasound imaging, which can be used to achieve reduced computational complexity with performance comparable to that of the Capon beamformer. The idea behind beamspace beamforming is that, instead of using the spatial statistics of the elements in the array to differentiate between signals and interference, we use the spatial statistics of a set of orthogonal beams, which are formed in different directions. This represents a shift from element space to beamspace. Because the majority of interference in medical ultrasound imaging is constrained to a limited spatial interval due to the focused transmit beam, this latter space can be reduced to a dimension that is lower than that of element space. We show, using simulations and experimental data, that this dimension can be selected as low as 3 while still achieving performance comparable to its element space counterpart.     

基于波束空间的改进TOPS宽带DOA估计

提出了一种基于波束空间的改进投影子空间正交性测试算法,以克服投影子空间正交测试(Test of Orthogonality of Projected Subspace,TOPS)算法在低信噪比时容易出现伪峰的缺点。通过对TOPS算法中的正交性测试矩阵添加对角修正矩阵,并利用波束空间方法对阵元接收数据进行预处理,从而实现对宽带信号的波达方向估计。仿真结果表明,文中所提出算法与TOPS算法相比,能够抑制波束指向范围内的伪峰,并能提高分辨概率和减少运算量,是一种具有应用前景的新算法。     

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。     

Beamspace blind signal separation for speech enhancement

Signal processing methods for speech enhancement are of vital interest for communications equipments. In particular, multichannel algorithms, which perform spatial filtering to separate signals that have overlapping frequency content but different spatial origins, are important for a wide range of applications. Two of the most popular multichannel methods are blind signal separation (BSS) and beamforming. Briefly, (BSS) separates mixed sources by optimizing the statistical independence among the outputs whilst beamforming optimizes the look direction of the desired source(s). However, both methods have separation limitations, in that BSS succumbs to reverberant environments and beamforming is very sensitive to array model mismatch. In this paper, we propose a novel hybrid scheme, called beamspace BSS, which is intended to compensate the aforementioned separation weaknesses by jointly optimizing the spatial selectivity and statistical independence of the sources. We show that beamspace BSS outperforms the separation performance of the conventional sensor space BSS significantly, particularly in reverberant room environments. K.F.C. Yiu is supported by RGC Grant PolyU. 7191/06E and the research committee of the Hong Kong Polytechnic University.     

基于矢量水听器阵的恒定束宽波束形成器的原理与设计

摘要：在对水下目标进行探测识别的应用中，一般要求声纳系统具备在较宽频带内形成恒定束宽波束的能力：过去对声纳恒定束宽波束形成器的研究一直针对声压水听器阵，近来随着对矢量水听器认识的深入，开展基于矢量水听器阵的恒定束宽波束形成器研究越发变得必要。本文正是体现了作者在这一方面的阶段性研究成果。文中首先介绍了单个矢量水听器的指向特性，接着提出了矢量水听器阵宽带恒定束宽波束形成器的实现原理和设汁方法，并以均匀等间距线阵为例，给出了获得实现恒定束宽算法所需频域加权矩阵的步骤，之后又进一步给出了恒定束宽算法的频域实现流程，并通过计算机仿真验证了其有效性：     

基于波束域相干信号子空间法的宽带源小尺度基阵定向

在给定的小尺度平面四元阵的基础上,主要研究了波束域相关信号子空间算法(BeamSpaceCoherentSignal-subspaceMethod—BSCSM)在宽带源定向中的应用以及性能分析。用实测的直升机噪声仿真产生各个阵元上输出的宽带信号源,并且使得这组信号具有特定的波达方向(DirectionofArrival—DOA)。分别使用波束域相干信号子空间法(BSCSM)和阵元域的相干信号子空间法(CoherentSignal-subspaceMethod—CSM)与非相干信号子空间法(InCoherentSignal-subspaceMethod—ICSM),通过计算机仿真实验对其进行方位估计。在仿真实验中,可以直观地看出三种方法的性能优劣。根据计算机仿真结果,统计意义上的误差分析,以及对宽带平面波波达角度的角度分辨率等性能指标的分析比较,可以得出在小尺度基阵定向研究中,波束域方法能够获得比其他两种阵元域算法更好的性能。     

Fingerprint-Based Millimeter-Wave Beam Selection for Interference Mitigation in Beamspace Multi-User MIMO Communications

Millimeter-wave communications are suitable for application to massive multiple-input multiple-output systems in order to satisfy the ever-growing data traffic demands of the next-generation wireless communication. However, their practical deployment is hindered by the high cost of complex hardware, such as radio frequency (RF) chains. To this end, operation in the beamspace domain, through beam selection, is a viable solution. Generally, the conventional beam selection schemes focus on the feedback and exhaustive search techniques. In addition, since the same beam in the beamspace may be assigned to a different user, conventional beam selection schemes suffer serious multi-user interference. In addition, some RF chains may be wasted, since they do not contribute to the sum-rate performance. Thus, a fingerprint-based beam selection scheme is proposed to solve these problems. The proposed scheme conducts offline group-based fingerprint database construction and online beam selection to mitigate multi-user interference. In the offline phase, the contributing users with the same best beam are grouped. After grouping, a fingerprint database is created for each group. In the online phase, beam selection is performed for purposes of interference mitigation using the information contained in the group-based fingerprint database. The simulation results confirm that the proposed beam selection scheme can achieve a signal-to-interference-plus-noise ratio and sum-rate performance which is close to those of a fully digital system, and having much higher energy efficiency.     

Implementation of broadband low-sidelobe beamforming in time domain

In modern active and passive sonar systems, broadband beamforming for acoustic arrays is widely used to suppress unwanted interference and to detect target signals of interest. A broadband low sidelobe beamforming scheme in time domain is proposed in this paper. The first step of this scheme is to delay the outputs of each element in the acoustic array by a tapped-delay-line (TDL) to accomplish the integer part of the time delay need to form a beam. Then, finite impulse response (FIR) digital filters are used to implement the fractional part of the time delay. The weighting coefficients for all array elements at different frequencies to realize the low sidelobe beams are also implemented with the FIR digital filters. Finally, the outputs of the digital filters are summed up to yield the time domain beam output. The design of low sidelobe beam pattern and that of the FIR digital filters are two crucial technical issues in this beamforming procedure. The low sidelobe beams of each sub-band are designed using the optimized beam synthesis approach based on the principle of MVDR beamforming. An improved adaptive approach are used for the design of FIR digital filters, and the design requirements of these filters were specified by the weights of low sidelobe beams of each sub-band over the broad frequency band. Results of computer simulation for a twelve-element arc array show that the beamforming scheme is very effective in forming low sidelobe broadband beam.     

声纳输出的弱目标信息提取方法仿真分析

针对存在艇外平台强干扰的情况,对波束域MVDR（b-MVDR）和后置波束形成干扰抵消器（PIC）的弱目标提取能力进行了仿真分析。考虑到艇外平台与目标往往处于同一波束的实际情况,提出首先采用密集波束形成,再进行弱目标提取的方法。仿真结果表明：对艇外平台与目标处于同一波束的情况,PIC的目标分辨能力更强;在干扰较强时,PIC方法表现出更强的弱目标提取能力,但随信干比的增加其能力不断降低;而b-MVDR方法则在各种信干比下均具有良好的性能。     

矢量水听器阵列虚拟阵元波束形成

在信号频率一定的情况下,常规波束形成方法需要通过增大基阵孔径来提高目标方位的估计精度,但这会受到实际工程应用的限制。在研究矢量水听器波束形成的基础上,提出了基于Taylor级数展开的虚拟阵元波束形成方法。该方法针对有限尺度双十字阵型的矢量水听器基阵,根据已知阵元接收的数据,运用Taylor级数展开方法估计虚拟阵元上的接收数据,使基阵孔径在虚拟意义上得以扩大。从而改善了阵列的波束性能,窄化主瓣和抑制旁瓣,实现了空间分辨率的提高。仿真和试验数据结果证明了该方法的有效性。