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针对多输入多输出声呐在水下探测场景中获得的空时快拍数量不足导致空时自适应检测性能下降的问题, 提出一种适用于小空时快拍数情况下的稳健空时自适应检测(STAD)方法。首先将斜对称特性推广到多输入多输出(MIMO)声呐空时自适应检测中, 并利用该特性将空时快拍数量扩展至原来的两倍; 然后利用迭代自适应方法实现对空时协方差矩阵的重构; 最后根据广义似然比检测(GLRT)准则推导出检验统计量。计算机仿真结果表明, 所提方法可以在小空时快拍数情况下准确估计空时协方差矩阵, 大幅减小空时自适应检测对空时快拍数量的需求, 提高多输入多输出声呐在小空时快拍数情况下的检测稳健性。 相似文献
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并列式多入多出(Multiple-Input Multiple-Output,MIMO)声纳可以通过高分辨波束形成方法进一步提高方位分辨能力。本文通过对窄带方法的扩展,提出一种宽带高分辨波束形成的方法,数值仿真分析了该方法的性能,并通过湖试数据进行了验证。结果表明,该方法可以对并列式MIMO声纳进行宽带高分辨波束形成,高信噪比情况下可以得到较高的方位分辨能力,但方位分辨力随信噪比减小下降较快,且运算量远大于常规波束形成方法,在运算能力满足要求且信噪比较高时,用本方法可显著提高系统的方位分辨性能。 相似文献
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实际多输入多输出(MIMO)声纳系统由于环境或人为因素,可能出现部分阵元失效,从而导致阵列自由度减少、方位估计精度下降。本文提出了一种数据协方差矩阵重构方法,该方法基于差分阵列性质,利用正常工作阵元的协方差矩阵元素来恢复失效阵元的矩阵元素,获得满秩的数据协方差矩阵,从而恢复到全阵元MIMO声纳的阵列自由度。与已有方法相比,降低了计算复杂度。仿真及海试实验数据处理结果表明,本文所提的数据协方差矩阵重构方法能够恢复因部分阵元失效而丢失的阵列自由度,应用于方位估计中,所能分辨的最大目标数与全阵元相同。 相似文献
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为提高电磁信号的到达角度以及多普勒效应等信道参数估计的准确性,在散射体非均匀分布下引入了散射概率和有效散射体两个物理概念,提出一种合理的改进型空间信道模型,该模型能准确地描述宏小区(macrocell)和微小区(microcell)等各种移动通信环境下的重要空时信道参数,并应用于多入多出系统(multiple input multiple output,MIMO)信道性能仿真中.数值仿真结果与早期多径衰落信道模型对比,表明本模型的信道参数估计结果符合理论和经验,拓展了空间统计信道模型的研究和应用,对评估多天线MIMO系统空时处理算法和仿真无线通信系统提供有力的工具. 相似文献
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为了研究波形分集和发射子阵对多输入多输出(multiple-input multiple-output:MIMO)声呐方位分辨力的影响,建立了同时适用于MIMO声呐和传统有源声呐的远场和近场波束图推导模型,证明了这两种声呐具有相同的方位分辨力。首先,将MIMO声呐发射阵划分为子阵无重合与子阵有重合两种情况,并对传统有源声呐的发射阵也进行相同的划分。据此,推导出两者的远场和近场阵列流型向量均可表示为发射与接收阵列流型向量的直积。接着,利用阵列流型向量的一致性证明了波束图(远场和近场)的一致性。进一步地,证明了发射子阵有重合的情况等效于对发射阵列进行幅度加权(发射阵列中间部分的阵元权值大于两端部分的阵元权值),其可获得更低的波束图旁瓣级但不能提高方位分辨力。理论分析与仿真结果表明:MIMO声呐的有效孔径等于发射与接收联合孔径,其方位分辨力由发射与接收阵列结构所决定,波形分集和发射子阵并未带来更高的方位分辨力。 相似文献
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The paper considers the problem of precise measurement of the acoustic radiation force of an ultrasonic beam on targets in the form of solid spherical scatterers. Using known analytic relations, a numerical model is developed to perform calculations for different sizes of spherical scatterers and arbitrary frequencies of the incident acoustic wave. A novel method is proposed for measuring the radiation force, which is based on the principle of acoustic echolocation. The radiation force is measured experimentally in a wide range of incident wave intensities using two chosen methods differing in the way the location of the target is controlled. 相似文献
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礁石和海洋动物引起的混响是主动声纳最严重的干扰, 如何区分礁石、鱼群和水中目标一直是制约主动声纳识别技术的难点问题. 针对礁石与目标回波难以区分的问题, 从特征识别的应用角度, 研究水中复杂目标全方位回波亮点特征的有效表征和应用方式, 基于目标回波亮点模型, 提出拷贝相关器输出的目标散射函数估计方法, 给出对目标回波亮点相对关系进行定量分析的目标回波特征统计表征方式, 并基于湖上实验提取了物理机理明确的目标回波亮点统计特征, 使得目标时间-角度谱中所蕴含的目标特征信息能够很直接地转化为主动声纳易于应用的目标特征.
关键词:
水中目标
回波亮点
统计特征 相似文献
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为了提高对浅海静止小目标的探测能力,提出了将多输入多输出和时反处理相结合的波导声呐处理框架。利用收发合置垂直阵,假设目标为点目标,每一个阵元轮流时反发射正交信号照射目标,整个阵接收对应的目标回波。当所有的阵元发射正交信号结束以后,对所有接收的目标回波数据进行分集处理,然后与时反发射驾驶向量做匹配滤波完成对目标的定位。分时发射策略克服了水声信道时延扩展和多普勒扩展导致常规多输入多输出处理接收端不同回波信号分离的困难。采用物理时反发射和数值时反接收聚焦,有助于抑制混响、提高回混比。数值仿真和波导水池实验结果表明多输入多输出时反处理较常规的有源匹配场处理以更高的精度对波导中的目标进行定位。 相似文献
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Many problems of current interest in underwater acoustics involve low-frequency broadband sonar interrogation of objects near the sea surface or sea floor of a shallow-water environment. When the target is situated near the upper or lower boundary of the water column the acoustic interactions with the target objects are complicated by interactions with the nearby free surface or fluid-sediment interface, respectively. A practical numerical method to address such situations is presented. The model provides high levels of accuracy with the flexibility to handle complex, three-dimensional targets in range-independent environments. The model is demonstrated using several bottom target scenarios, with and without locally undulating seabeds. The impact of interface and boundary interactions is considered with an eye toward using the sonar return signal as the basis for acoustic imaging or spectral classification. 相似文献
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A measure of convergence of the Neumann series, originally obtained for isotropic spherical scatterers, has been adapted for systems of non-isotropic scatterers chosen to model a vegetation target. The measure is related to the ratio of successive terms in the absolute series formed from the Neumann series. Novel, fully polarimetric calculations have been performed of multiple far-field scattering between realistic objects. The simulations indicate that the convergence measure provides a good indicator of when low-order truncations of the series are sufficient for backscatter calculations. At the same time, the distribution of backscattered intensity has been determined and its dependence upon truncation order investigated. The distributions are seen to be dependent on truncation order only when the scattering series is weakly convergent. 相似文献
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Foote KG 《The Journal of the Acoustical Society of America》2012,131(5):3698-3709
Measurement of acoustic backscattering properties of targets requires removal of the range dependence of echoes. This process is called range compensation. For conventional sonars making measurements in the transducer farfield, the compensation removes effects of geometrical spreading and absorption. For parametric sonars consisting of a parametric acoustic transmitter and a conventional-sonar receiver, two additional range dependences require compensation when making measurements in the nonlinearly generated difference-frequency nearfield: an apparently increasing source level and a changing beamwidth. General expressions are derived for range compensation functions in the difference-frequency nearfield of parametric sonars. These are evaluated numerically for a parametric sonar whose difference-frequency band, effectively 1-6?kHz, is being used to observe Atlantic herring (Clupea harengus) in situ. Range compensation functions for this sonar are compared with corresponding functions for conventional sonars for the cases of single and multiple scatterers. Dependences of these range compensation functions on the parametric sonar transducer shape, size, acoustic power density, and hydrography are investigated. Parametric range compensation functions, when applied with calibration data, will enable difference-frequency echoes to be expressed in physical units of volume backscattering, and backscattering spectra, including fish-swimbladder-resonances, to be analyzed. 相似文献
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Feature extraction is a key step for underwater passive sonar target classification and recognition.A kind of tensor feature extraction method based on auditory PattersonHoldsworth cochlear model is proposed.First,the filter impulse response of the cochlear model is regarded as the basis function of signal decomposition,and the center frequency of different channels is determined according to the nonlinear scale or conventional linear scale of the auditory model.Then,the gain and bandwidth of th... 相似文献
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特征提取是水下无源声呐目标分类识别的关键步骤,提出了一种基于听觉Patterson-Holdsworth耳蜗模型的听觉域张量特征提取方法。将耳蜗模型的滤波器冲激响应视为信号分解的基函数,根据听觉模型非线性尺度或常规线性尺度确定不同通道的中心频率,然后计算出相应通道的增益和带宽,并量化冲激响应的阶数和相位参数,得到信号分解基,再根据信号分解原理得到通道数×阶数×相位数的三阶张量特征,并通过计算测试样本张量特征与训练样本张量特征间的相似性实现了水下无源声呐目标的分类识别。海上实录无源声呐目标的分类识别实验表明,提取的张量特征具有比较好的分类识别性能,听觉模型等效矩形带宽尺度优于线性尺度划分中心频率,能够提高无源声呐的目标指示能力。 相似文献
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A computational sensorimotor model of target capture behavior by the echolocating bat, Eptesicus fuscus, was developed to understand the detection, localization, tracking, and interception of insect prey in a biological sonar system. This model incorporated acoustics, target localization processes, flight aerodynamics, and target capture planning to produce model trajectories replicating those observed in behavioral insect capture trials. Estimates of target range were based on echo delay, azimuth on the relative intensity of the echo at the two ears, and elevation on the spectral pattern of the sonar return in a match/mismatch process. Flapping flight aerodynamics was used to produce realistic model trajectories. Localization in all three spatial dimensions proved necessary to control target tracking and interception for an adequate model of insect capture behavior by echolocating bats. Target capture using maneuvering flight was generally successful when the model's path was controlled by a planning process that made use of an anticipatory internal simulation, while simple homing was successful only for targets directly ahead of the model bat. 相似文献
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TANG Weilin 《声学学报:英文版》1994,(2)
I.IntroductionTheecho-rangingapproachistheonlycffectiveapproachfordetectionandidentifi-cationofunderwatertargetifitisasilcntobkct.Echoformationisaphysicalprocessinwhichthetargetisexcitcdbyincidentwavc.Byechothecharactcristicinformationsoftargethavebcencarricd.Suchinformationsarejustfundamentalsofdetectionandiden-hficationappliedbyactivesonars.Classificationandidentificationareimportantdevelopmentsofreccntsonarsin-c1udingthehomersoftorpedocs.Thisneedsadecpunderstandingrcferredtoechobe-haviors… 相似文献
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针对水下多基地目标识别问题,提出了基于特征预测和误差映射的多基地融合识别算法。推导并简化了基于贝叶斯公式的多基地目标识别条件概率公式,利用BP神经网络对最后一个节点的特征向量进行预测,并计算得到预测值与实际值误差的概率密度,将其与前面每个节点的条件概率累乘,以得到目标识别的条件概率。将利用特征预测计算条件概率的方法从单个节点推广到多个节点上,同时针对误差概率分布模型不准确的问题,提出了利用混合高斯分布模型代替单高斯概率分布模型的改进方法。对每个目标重复此过程,取结果最大值对应的目标类别为最后的识别结果.在消声水池开展多基地模拟实验,对四类目标进行识别,在一定声呐节点数目及信噪比条件下,与单基地声呐相比,多基地目标融合识别得到的识别正确率最大可提高40%,采用改进方法以后,识别正确率得到进一步提高。 相似文献
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