共查询到19条相似文献，搜索用时 302 毫秒
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分段拷贝相关器是高斯白噪声背景下,快速衰落水声信道中,对应最大似然比准则的最佳接收机,其输出服从χ2分布。推导出有信号时接收机输出端的概率密度函数和检测概率的解析表达式,计算机仿真结果验证了所获得结果的正确性。最后通过计算无信号时接收机输出的概率密度函数,在给定虚警概率的情况下,求出了接收机的检测门限。 相似文献
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在高斯白噪声背景下,匹配滤波器作为线性调频信号的最优检测器,在水声信号处理中被广泛应用。 当发射信号为线性调频信号时,由水下目标径向速度引起的多普勒频移会造成回波和样本之间失配, 使匹配滤波器的检测性能下降,增加了目标速度估计的难度。 利用分数阶傅里叶变换对于线性调频信号的聚焦特性,提出了应用分数阶傅里叶变换的水下运动目标线性调频回波检测算法,完成对目标速度的估计, 推导目标运动速度与分数阶傅里叶变换阶数之间的关系,并对测量结果进行误差分析。 仿真测试表明,该算法可有效地估计混响背景下的目标径向速度,且具有良好的估计性能。 相似文献
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舰艇目标航行时往往向水中辐射大量线状谱结构的声波信号,线谱信号检测对舰艇目标的被动探测至关重要。实际水下环境噪声常表现为时域非平稳噪声,常规离散傅里叶变换类线谱检测方法时域积分时,不可避免会引入非平稳噪声背景中出现的短时强干扰噪声,使积分结果中线谱信噪比大幅降低,线谱检测性能急剧恶化。为解决上述问题,对分段离散傅里叶变换结果进行幅度归一化,补偿分段线谱信号间相位差,提出了一种非平稳噪声背景下的线谱相干检测方法。仿真结果表明,相比常规 DFT 类线谱检测方法,所提方法能够降低时域非平稳背景噪声起伏影响,具有更优的非平稳噪声背景下线谱检测性能,并能获得对线谱信号的相干处理增益。 相似文献
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尾流自导鱼雷对水面舰艇构成严重威胁。 为了把悬浮拦截弹被动拦截方式从非尾流区域扩展到尾流区，拦截尾流自导鱼雷，需要研究尾流内噪声特点，分析出拦截弹在尾流区的环境噪声特性。 基于悬浮拦截弹对不同吨位舰船尾流噪声进行研究，结合高阶累积量从概率论的角度出发，计算了尾流噪声的斜度和峰度随尾流年龄的变化规律；噪声斜度判断噪声是否满足对称分布，峰度判断噪声是否为高斯信号。 将实测数据与仿真数据峰度和斜度进行比对，得出结论：舰船尾流噪声环境可以近似看作是高斯信号，服从对称分布，且该分布特性与舰船吨位不相关。 相似文献
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目标触底过程中通常会产生强烈的瞬态地震波信号,通过对此类地震波信号的监测、处理和分析,能够帮助判断该信号的产生是否是由异常活动产生的,并且能够根据信号分析相关信息,实现早期预警, 从而做出快速响应。 由于双谱检测具有很好的抗高斯干扰能力,对高斯平稳随机过程和试验模拟目标触底瞬态地震波信号的双谱特性进行了分析,并在高斯背景中对试验采集的瞬态信号进行了检测仿真,仿真试验结果表明:在高斯背景的干扰下,双谱检测能够有效实现对瞬态信号的检测[1] 。 相似文献
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在基于移动 AUV(自主水下机器人)平台的水下机动目标探测场景中,由于拖曳能力和探测孔径的限制,目标噪声极易淹没在本体噪声中。而且,本体噪声与目标噪声具有非常相似的频谱特性和倍频关系,进一步加重了目标噪声分析的难度。为降低本体噪声的影响、提高目标噪声的信噪比,开展了基于 U-Net 深度网络的水下混合噪声信号分离算法研究。通过仿真模型测试了算法在不同转速差、桨叶数差以及目标噪声信噪比条件下去除本体噪声的性能。实验结果初步表明：在目标信号信噪比不低于–10 dB 的条件下,算法可以对本体噪声进行有效去除。 相似文献
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根据舰船辐射噪声频域特性，从舰船辐射噪声线谱、谱密度的发展变化趋势、特征频段信号能量 3 个方面考虑，对舰船辐射噪声仿真数据和实测数据进行一致性分析，综合评估舰船辐射噪声仿真模型置信度。通过对舰船辐射噪声仿真模型置信度分析，为舰船辐射噪声仿真信号源置信度提供理论支撑。 相似文献
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由于传统情况,匹配场处理器主要针对接收信号为高斯信号,而海洋环境中存在大量的有色噪声,因此设计基于高阶累积量的匹配场处理器具有一定价值。本文介绍了一种在海洋声层析环境下用高阶累积量来降低匹配场处理中高斯有色噪声的算法,对比研究了基于高阶累积量的简正波声场匹配场处理器、传统线性匹配场处理器、自适应匹配场处理器及二阶MUSIC算法匹配场处理器在相同声场环境条件下的匹配场定位效果。研究结果表明,在不考虑参数失配与计算量前提下,接收信号经过基于高阶累积量的简正波声场匹配场处理器后再进行匹配场定位,能有效降低旁瓣,且使用高阶累积量可显著消除海洋传播环境中高斯有色噪声和高斯白噪声对信号的干扰,其匹配效果优于另外三种匹配场处理器。 相似文献
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Underwater noise due to snapping shrimp is highly impulsive, and often dominates the ambient noise environment of warm, shallow waters at frequencies above 1 kHz. We report here on the statistics of bandpass snapping shrimp noise data, and on the modeling of the joint distribution of the in-phase and quadrature components using bivariate versions of the generalized Gaussian (GG), generalized Cauchy, and Gaussian-Gaussian mixture models. We evaluate the performance of several generalized energy detectors for passive bandpass detection, by inserting stochastic signals into the noise data. Detection thresholds were measured for an integration time of 0.5 s and false alarm probabilities down to 1%. The locally optimum detector based on the mixture model gave the best weak signal detection performance, with an 8 dB reduction in detection threshold over conventional energy detection. A significance test detector based on the GG model performed 1-2 dB worse, but exhibited better strong signal performance 相似文献
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The optimal detection of signals requires detailed knowledge of the noise statistics. In many applications, the assumption of Gaussian noise allows the use of the linear correlator (LC), which is known to be optimal in these circumstances. However, the performance of the LC is poor in warm shallow waters where snapping shrimp noise dominates in the range 2-300 kHz. Since snapping shrimp noise consists of a large number of individual transients, its statistics are highly non-Gaussian. We show that the noise statistics can be described accurately by the symmetric alpha-stable family of probability distributions. Maximum-likelihood (ML) and locally optimal detectors based on the detailed knowledge of the noise probability distribution are shown to demonstrate enhanced performance. We also establish that the sign correlator, which is a nonparametric detector, performs better than the LC in snapping shrimp noise. Although the performance of the sign correlator is slightly inferior to that of the ML detector, it is very simple to implement and does not require detailed knowledge of the noise statistics. This makes it an attractive compromise between the simple LC and the complex ML detector 相似文献
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Hard limiting or sign detection schemes for low-pass known and random signals in additive noise are popular as very simple signal detectors maintaining constant values for their false-alarm probabilities under the rather weak assumption that the sampled noise observations have zero median values. For nonparametric detection of narrow-band signals the natural extension of the zero medians assumption is the zero marginal medians assumption on the in-phase and quadrature noise components. Nonparametric detectors operating under this assumption are developed here for narrow-baud signals; these can be taken to be the logical counterparts of the low-pass sign correlator and polarity coincidence correlator detectors of low-pass theory. The concept of conditional testing, which has been applied previously to obtain efficient multilevel versions of low-pass sign detection schemes, is shown to enter quite naturally in the definition of narrow-band counterparts of the sign correlator and the polarity coincidence correlator detectors. It is also shown that under the diagonal symmetry extension of the low-pass univariate symmetry condition on the noise probability density function, multilevel extensions of these conditional test narrow-hand detectors may also be defined as counterparts of the multilevel conditional test schemes for low-pass signals. 相似文献
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This paper presents an evaluation of second, third, and fourth-order moments for the passive detection of transient signals in both simulated Gaussian noise and measured noise. The measured noise was recorded by a vertical array located near the San Diego, CA, harbor and is dominated at low frequencies by ship-generated noise. The detectors assume neither noise nor signal stationarity and can use single or multiple channels of data. Simulation results indicate that the fourth-order moment detector often performs better than the energy detector in the correlated measured noise, with increasing channel contributions to the moment function, resulting in increased gain. The results in simulated Gaussian noise likewise favor the fourth-order moment detector, at least for the signals with significant fourth-order moments, but the ability of the higher order detector to discriminate against correlated noise is evident. Analysis over a 30-min segment of the measured noise with selected signals demonstrates that fourth-order detection gains can be reliably expected as the noise statistics change. 相似文献
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The detection of known and partially known signals in additive white Gaussian uonstationary noise is considered, with primary attention to the ease where the time-varying noise intensity parameter N_{o}(t) is a periodic function. Optimum receiver structures are derived for three detection cases, namely completely known signals, sinusoids with random phase, and sinusoids with both random amplitude and phase. It is demonstrated that optimum receiver performance can be achieved only if proper synchronization to the noise intensity N_{o}(t) is accomplished. Large performance penalties can be demonstrated when an improperly synchronized receiver is used. Consequently, suboptimum receivers that ignore the noise intensity time variations and therefore require no synchronization, have been considered, and their performance compared to their optimum counterparts. Depending on the type of time-varying noise intensity being considered, results show that performance differences between optimum and suboptimum receivers can be negligible in some cases, and yet can be substantial in other cases. Several examples have been worked out using two different forms for N_{o}(t) and corresponding performance evaluations have been carried out and presented graphically in terms of receiver error probability as a function of signal-to-noise ratio. 相似文献
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Several detection statistics are compared in the frequency domain based on the asymptotic probability of detection (APD) criterion. They include second-order, fourth-order, normalized fourth-order, and kurtosis estimates. The results show that for randomly occurring signals which can be characterized as non-Gaussian, the fourth-order, normalized fourth-order, and kurtosis estimates can have higher asymptotic probability of detection levels compared with second-order estimates. But only for the normalized fourth-order and kurtosis estimates do the results seem significant. Moreover, if a second-order estimate of the noise is available to normalize a fourth-order estimate of signal and noise, the resultant normalized fourth-order estimate has higher asymptotic probability of detection levels even for Gaussian signals. This result holds only when there is a significant positive covariance between the numerator and the normalizing noise sample in the denominator. On the other hand, if an independent noise sample is used to normalize a second-order or fourth-order estimate, the overall performance based on the asymptotic probability of detection will be degraded compared with the unnormalized second-order or fourth-order estimates, respectively. 相似文献
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A unified treatment for performance evaluation of various array signal processors is presented. Detection performance is expressed in terms of the parameter of the power-type receiver operating characteristic (ROC) for optimum, beamformer, and null-steerer detectors. Estimation performance is analyzed in terms of the normalized mean-square error (MSE) for minimum mean-square error (MMSE) and maximum likelihood estimators (MLE's) under a varying noise environment. Sensitivity of the detection/estimation performance to the varying internal and directional noise sources is investigated. An interesting inverse relationship is presented between the normalized MSE of the MMSE estimator and the power-type ROC parameter for the optimum detector. 相似文献
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A method for estimating the amplitude and time-delay parameters for signals that can be represented as a sum of a number of scaled and delayed replicas of a known signal in the presence of nonwhite Gaussian noise is presented. The method is based upon the principles of maximum likelihood (ML) estimation, but at certain key points simplifying assumptions are made that result in a computationally practical estimation scheme. The results are compared with other related results in the literature. Simulation results are presented which support the methods derived. 相似文献
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Channel Modeling and Threshold Signal Processing in Underwater Acoustics: An Analytical Overview 总被引：1，自引：0，他引：1
An overview of underwater acoustic channel modeling and threshold signal processing is presented, which emphasizes the inhomogeneous, random, and non-Ganssian nature of the generalized channel, combined with appropriate weak-signal detection and estimation. Principal attention is given to the formal structuring of the scattered and ambient acoustic noise fields, as well as that of the desired signal, including both fading and Doppler "smear" phenomena. The role of general receiving arrays is noted, as well as their impact on spatial and temporal signal processing and beam forming, as indicated by various performance measures in detection and estimation. The emphasis here is on limiting optimum threshold systems, with some attention to suboptimum cases. Specific first-order probability density functions (pdf's) for the non-Ganssian components of typical underwater acoustic noise environments are included along with their field covariances. Several examples incorporating these pdf's are given, to illustrate the applications and general methods involved. The fundamental role of the detector structure in determining the associated optimum estimators is noted: the estimators arc specific linear or nonlinear functionals of the original optimum detector algorithm, depending on the criterion (i.e., minimization of the chosen error or cost function) selected. Results for both coherent and incoherent modes of reception are presented, reflecting the fact that frequently signal epoch is not known initially at the receiver. To supplement the general discussion, a selected list of references is included, to provide direct access to specific detailed problems, techniques, and results, for which the present paper is only a guide. 相似文献