一种基于多普勒频移的被动合成孔径声纳探测方法*

由于自主小平台声纳孔径有限,对声纳探测的分辨率的提高有所限制。小平台的机动可以有效的与声纳探测方法相结合来提高声纳探测性能。针对这一特点,提出一种基于多普勒频移技术的被动合成孔径声纳探测方法。该方法根据自主小平台的机动所引起声纳的接收信号多普勒频移的变化,进行目标的频率与方位联合估计。本文将自主小平台的机动引入到波束形成技术当中形成一种新的被动合成孔径技术。数值仿真表明,该方法可以有效的进行目标方位估计,并且获得较高的方位分辨率,改善了自主小平台的探测性能。     

峰值能量检测及其在被动声纳显示中的应用

本文介绍子带峰值能量检测方法及其在被动声纳显示和检测中的应用[2-4]，同时提出了波束域宽带峰值能量检测算法。新的波束域算法是在已有波束形成的基础上进行处理，不需对原系统进行较大的修改。通过波束域宽带峰值能量检测处理，可以改善声纳显示效果，更加清晰地显示目标方位。相对于高分辨率波束形成算法，两种峰值能量检测算法的运算量都比较低，具有一定的工程应用前景。通过计算机仿真和实测数据处理，验证了所述两种峰值能量算法在提高显示清晰度，减小测向模糊度方面的优点。     

逆波束形成在圆阵中的应用

本文讨论将逆波束形成算法应用于圆阵,给出了圆阵FIM（Fourier Intergral Method）积分方程的近似解,并通过滑动平均进一步改善了逆波束形成算法。仿真结果表明：本文所采用的逆波束形成算法旁瓣比常规波束形成算法低4dB,空间方位分辨力提高约1／3。算法的性能通过海试数据处理得到了进一步验证。     

阵列结构下的低频信号合成方法研究

基于高频天线产生低频电磁波信号,实现多波段信号对目标的照射,不仅有可能减小低频天线尺寸,而且可能成为提高雷达目标探测性能的一种途径.本文将多普勒效应与阵列天线结构相结合,基于对阵列中各辐射单元的信号时序、相位和间距等参数的控制,提出了一种在目标区产生低频信号的方法.本文给出了阵列参数的选择原则,介绍了目标位于阵列方向和45°角扫描时的低频信号合成情况,对存在辐射单元间距误差、相位误差、目标偏离预定位置以及等间隔稀疏条件下的合成信号性能进行了分析,并采用峰值旁瓣比和积分旁瓣比来评价合成信号的性能.将频率1 GHz载波信号合成为频率400 MHz信号的仿真分析结果,表明了本文方法的有效性.     

X波段16单元矩形径向线螺旋阵列天线设计

研究了一种X波段16单元矩形径向线螺旋阵列天线。介绍了该矩形阵列天线的提出背景以及工作原理,分析了两种电磁耦合探针在X波段的耦合特性,开展了扼流结构与电磁耦合探针的协同设计,设计并数值模拟了中心频率为9.3 GHz的16单元矩形径向线螺旋阵列天线,并进行实验测试。测试结果表明：该口径为96 mm96 mm的天线在中心频率9.3 GHz下,增益为19.51 dB,轴向轴比值1.05,驻波系数1.17。     

X波段16单元矩形径向线螺旋阵列天线设计

研究了一种X波段16单元矩形径向线螺旋阵列天线。介绍了该矩形阵列天线的提出背景以及工作原理,分析了两种电磁耦合探针在X波段的耦合特性,开展了扼流结构与电磁耦合探针的协同设计,设计并数值模拟了中心频率为9.3 GHz的16单元矩形径向线螺旋阵列天线,并进行实验测试。测试结果表明:该口径为96 mm×96 mm的天线在中心频率9.3 GHz下,增益为19.51 dB,轴向轴比值1.05,驻波系数1.17。     

温跃层及其变化对被动声纳检测概率的影响

根据被动声纳工作原理,构建被动声纳探测水下目标物概率数学模型。利用声学调查实测数据,综合考虑传播损失、环境噪声、和水文环境分布及季节变化,研究温跃层垂直分布及季节变化对声纳检测概率的影响。结果表明:温跃层对被动声纳影响巨大,逆温跃层环境中,声纳检测概率从海表向下逐渐减小;正温跃层对声纳总的影响与逆温跃层相反,在正温跃层上界,检测概率从表层向下先减小后增大;逆温跃层对被动声纳检测概率的影响随目标物与声纳距离的增大而增大,正温跃层影响相反。     

扩展拖曳阵宽带频域逆波束形成技术研究

为了提高扩展拖曳阵在低信噪比下对目标的探测性能,本文将基于扩展拖曳阵方法的被动合成孔径技术与宽带频域逆波束形成技术进行了结合,形成了一种新的被动合成孔径测向技术,有效地提高了扩展拖曳阵技术的探测性能,改善了传统基于被动合成孔径测向技术在低信噪比下性能急剧下降的问题,在低信噪比下获得了更高的方位分辨率,同时对于多目标及弱目标检测能力也更为优异。计算机仿真和海试数据的处理都证明了这一算法的良好性能。     

采用空间谱加权稀疏约束的稳健Capon波束形成方法

针对标准Capon波束形成器旁瓣级高以及期望信号方向存在误差时,性能会严重下降的问题,提出一种基于噪声及干扰空间谱加权的稀疏约束Capon波束形成方法。该方法利用波束响应本身具有的稀疏特性,以及在稀疏重构算法中l₁范数具有抑制较大值保护较小值的特性,使用噪声及干扰的空间谱对不同角度的波束响应进行加权,然后施以稀疏约束。仿真、水池试验与湖上试验中,与其它几种方法比较表明该方法可以降低波束形成器的旁瓣级,获得较深的零陷,提高了阵列输出信干噪比与抗导向向量误差的能力。     

一种水下未知固定深度的被动目标运动分析

本文对水下三维情形的被动目标运动分析（TMA）进行了探讨。文中使用的数据量测是关于目标的方位角、俯仰角和多卜勒频移等,且运动目标与观测平台相对深度固定未知。这是水下一种常见的三维情况。伪线性估计和最大似然估计方法的处理结果表明：由于增大了观测的信息量,运动参数的估计方差收敛性较好,估计性能得到有效改善。伪线性方法的方差估计曲线向CBR界逼近。最后该方法也适合于分析已知固定深度的三维情形与同处一个水平面的二维情形等特殊情况。     

A passive synthetic aperture phase correction algorithm for the asymmetric twin-line array sonar

A passive synthetic aperture based on phase correction algorithm for solving the port-starboard discrimination problem in the non-aligned towed twin-line array sonar,is de- scribed.This method creates a virtual array through applying the estimated phase correction into one array of twin-line arrays.Because the synthetic virtual array is aligned with the other array in twin-line arrays,the right port-starboard discriminated results can be obtained by array processing based on the new synthetic twin-line array.The effect of proposed method has been shown by simulated and sea-trials results in towed twin-line array sonar.With low extra computational loads,the proposed method is easy to apply to the practice.     

Irregular array motion and extended integration for the suppression of spatial aliasing in passive sonar

Conventional synthetic aperture processing uses motion of the sonar to increase aperture size and bearing resolution. Two recent papers discussed a different application in which synthetic elements are used to fill in an otherwise sparse passive array. This paper points out that ambiguities persist, even with synthetic elements, in the ideal case of a straight, uniform, sparse line array with constant velocity in the presence of plane wave signals. It is also shown that irregular motion such as acceleration introduces additional information which can be exploited to suppress the ambiguities. The degree of suppression in such an approach is independent of signal direction. If source stability supports extended coherent integration, then the acceleration and integration time required are both modest to achieve interesting levels of suppression. For a less stable source, a modified conventional beamformer is introduced which leverages acceleration over multiple snapshots to suppress the ambiguities. A post-beamformed processing stage involving a nonlinear deconvolution technique such as the CLEAN algorithm can further improve the result. A semi-coherent adaptation of CLEAN is shown to remove the residual ambiguities effectively in the presence of a moderate level of uncorrelated noise.     

The interference characteristics of platform and towed body noise in shallow water for active/passive towed array sonar

The interference characteristics of towed platform noise resulted from propeller and towed body for active/passive towed array is analyzed. It is shown that, in shallow water environment, the direct wave and bottom/sea surface reflected wave will seriously affect the performance of sonar system. The formula for calculating the direction of arrival (DOA) of interference in terms of various parameters, such as array depth, length of tow cable, is derived. The effect of interference noise for the detection performance of sonar system is described. The results of system simulation provide the method for reducing the effect of these kind of interferences.     

Striation-based beamforming for estimating the waveguide invariant with passive sonar

The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the ocean waveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striation-based beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.     

第四讲探潜先锋--拖曳线列阵声纳

文章介绍了在反潜战中发挥重要作用的拖曳线列阵声纳的工作原理、结构特点、系统组成,同时回顾了拖曳线列阵声纳从第一次世界大战时Hayes H C博士的概念到2000年John R.Potter等人的细线阵所经历的长达80年的发展过程,最后预计,应用光纤、新声源,采用多线阵结构能进行三维定位的主被动模块化拖曳线列阵声纳是未来的发展方向.     

相控阵超声二维稀疏阵列的优化设计应用研究

在相控阵超声检测中,稀疏阵列是利用较少阵元数目获得大阵列孔径的有效办法。目前一些稀疏阵列没计的方法,并没充分利用有效阵元。本文首先采用遗传算法没计二维稀疏阵列,发现遗传算法设计的稀疏阵列,一致性较差。主要原因是在没有任何限制的条件下,寻优搜索空间大,遗传算法参数往往难于控制。针对此问题,受十字形稀疏阵列和最小冗余度阵列的启发,本文将最小冗余度阵列拓展到二维稀疏阵列的设计中。计算机模拟和实验都表明,利用最小冗余度阵列和遗传算法设计的二维稀疏阵列具有很好的空间分辨率和对比度分辨率。     

Target recognition algorithm for passive sonar system with high generalization ability

1IntroductionTheshipradiatednoises,whichcombineplentyinformationoftargetcharacteristics,arethemajorevidenceintargetlocatingandrecognizingofpassivesonarsystem.Theautomatictargetrecognition(ATR)ofpassivesonaristheurgentrequirementofmodernnavalbattlesandthekeyresearchtopicofunderwateracousticsignalprocessing.Astheshipradiatednoiseisasomewhatcomplexnon-stationarystochasticsignalthatisoftencontaminatedbythe-.oceanicenvironmentnoise[6],itisdifficulttoestablishmathematica1modelofshipradiatednoise.T…     

Extraction of small boat harmonic signatures from passive sonar

This paper investigates the extraction of acoustic signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the harmonic structure of noise radiated from small boats is developed. The Harmonic Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the harmonic tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. Results are presented that show the HEAT algorithms ability to extract these signatures.     

Method of generating orthoscopic elemental image array from sparse camera array

We propose a method of generating orthoscopic elemental image array from a sparse camera array. A parallax image array obtained by a sparse camera array provides different perspectives of a real threedimensional (3D) scene, and has all the information the elemental image array needs. In-depth analysis of the generation method and the relationships between the sparse camera array and the elemental image array are presented. The experimental results demonstrate the correctness of the proposed method.     

Weak signal direction of arrival estimation for colocated multiple-input multiple-output sonar array

In order to suppress the influence of symmetrical noise component on multiple-input multiple-output(MIMO)sonar's direction of arrival(DOA)estimation under the condition of low signal-to-noise ratio,we propose a DOA estimation algorithm based on covariance matrix reconstruction method.Firstly,the noise field can be decomposed into symmetrical noise field and asymmetrical noise field.We utilize symmetry property of colored noise matrix and the feature that the imaginary part of covariance matrix has no relation with the symmetry noise to remove the real part of covariance matrix.This operation helps to suppress the influence of colored noise on DOA estimation accuracy.Based on the principle of the imaginary matrix part displacement and the dimension reduction transformation method,the real part of covariance matrix is reconstructed,which helps to suppress the bilateral spectrum interference.Thereafter,Toeplitz method is applied for the covariance matrix decorrelation amendment,and a noise subspace is formed by singular value decomposition(SVD).Finally,we can estimate the DOA of target signals.Both theoretical analysis results and numerical simulation results verify the symmetrical noise suppression performance of this algorithm,and the estimation performance of target azimuth is improved obviously.This method has the characteristics of lower operational complexity,higher degrees of freedom and stronger target resolution.