共查询到19条相似文献,搜索用时 109 毫秒
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针对传统舰载雷达和岸基雷达很难检测出海杂波背景下小目标的现状,提出一种基于Hurst指数差异的方法来检测海杂波背景下小目标。该算法基于小波分析法:计算各种极化方式下不同距离门的海杂波的Hurst指数,分析发现距离门含有小目标的Hurst指数明显大于距离门只含有海杂波的Hurst指数,而只含有海杂波的不同距离门间Hurst指数变化较小,因此可基于不同距离门的Hurst指数差值作为检测小目标的标准。实验证明,该算法可在没有任何先验知识条件较准确地检测出海杂波背景下的小目标。 相似文献
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实际的网络流量模型采用自相似模型,Hurst参数是序列长相关程度的度量。为方便工程上对网络流量的长相关性进行估计,介绍了网络流量自相似模型和Hurst参数小波分析法,建立了分数阶傅里叶变换(FrFT)与小波分析之间的联系,在此基础上介绍了一种新的基于FrFT的网络流量Hurst参数估计方法,并运用此方法设计了网络流量Hurst参数估计器。通过对白噪声和已知Hurst参数的实际网络流量数据进行估计,本方法可以有效估计随机时间序列的Hurst参数。 相似文献
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本文综合运用了傅立叶分析和小波分析两种方法,分别对人在情绪波动状态下和自然状态下的皮肤温度信号的波动特性进行了分析、比较,并且探讨了两种方法的不同估计特性以及各自在分析中的作用。结果表明:人体皮肤温度信号在两种状态下均呈现出1/f~α波动特性,可以用Hurst指数和分形维数来刻画。 相似文献
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本文主要研究海杂波频谱的扩展自相似特性及多尺度Hurst指数在海杂波目标检测中的应用.作为分数布朗运动的一种推广,扩展自相似过程采用多尺度Hurst指数来描述分形信号.多尺度Hurst指数可以描述分形信号在各尺度下的细节信息,弥补了单一Hurst指数只能从整体上描述分形信号粗糙度的不足.首先,本文在实测雷达数据基础上研究了海杂波频谱的扩展自相似性以及影响参数;然后,利用在最优频域尺度下海杂波频谱的多尺度Hurst指数对目标相对较敏感的特点设计恒虚警检测方法,实现海杂波中的目标检测.实测数据分析表明,海杂波频谱的多尺度Hurst指数比时域单一Hurst指数、时域多尺度Hurst指数具有更好的海杂波与目标区分能力,且由于Fourier变换可以有效提升信杂比,该检测方法具有检测海杂波中微弱运动目标的潜力. 相似文献
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分形高斯噪声FGN是分形布朗运动的增量过程,广泛应用于自相似过程的建模分析。在众多的合成分形高斯噪声的方法中,研究了基于功率谱的FGN的生成算法,谱模拟方法和Paxson方法的特点以及联系.同时对基于功率谱的Hurst指数的估计方法,周期图法进行了讨论。仿真试验中,使用Paxson方法生成了FGN序列数据.试验结果表明生成的FGN具有很好的自相似性。应用周期图法估计了其Hurst指数,相比方差时间法,周期图法在估计长相关过程的参数方面能够提高精度。 相似文献
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为了准确及时的进行DDoS攻击检测,提出了一种新的DDoS攻击检测算法。该算法在基于传统的小波分析检测DDoS攻击的基础上融入了主成分分析法和小波分析法中DDoS检测方法,并根据该算法设计相应的模型和算法来检测 DDoS 攻击,并且引入信息论中的信息熵对源IP地址的分散程度进行度量,根据初始阶段Hurst指数及熵值的变化自适应地设定阈值以检测攻击的发生。实验结果表明,该方法大幅度的提高了DDoS检测的速度。 相似文献
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采用二次小波变换自动阈值算法对局部放电信号进行提取。在数值仿真中,采用指数衰减或指数衰减振荡等4种放电信号,研究了局部放电信号的提取效果。仿真结果表明,由于小波变换具有多分辨率的特性,能有效地从随机噪声中提取出放电信号,较常规一次小波变换阈值消噪方法相比,二次小波变换更多地保留了原始局部放电信号的特征信息,该算法处理速度较快,也适合在线处理。 相似文献
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Cooklev Todor Nishihara Akinori Yoshida Toshiyuki Sablatash Mike 《Multidimensional Systems and Signal Processing》1998,9(1):39-76
In the paper new design methods for multidimensional two-channel perfect reconstruction (PR) FIR filter banks are described. The filters have linear phase, achieve an arbitrarily high number of vanishing moments and can be used to obtain biorthogonal wavelet bases. Two-dimensional wavelet bases with square, rectangular, and hexagonal support are constructed. A design method that trades off vanishing moments and frequency selectivity is described. These two properties are both important in subband coding, but they each require a share of the degrees of freedom available from the total number of filter coefficients. Novel analytic formulae are derived and are applied to provide illustrative examples. 相似文献
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A novel design of lifting scheme from general wavelet 总被引:5,自引:0,他引:5
Honggang Li Qiao Wang Lenan Wu 《Signal Processing, IEEE Transactions on》2001,49(8):1714-1717
A novel algorithm that is used to lift the vanishing moments of the wavelet from general wavelet, and not only from the Lazy wavelet, is proposed. It is based on the relationship between the vanishing moments of the wavelet and multiple of zeros of z=1 and only needs to solve simple linear equations to obtain the lifting coefficients. Moreover, the shortest lifting scheme and its uniqueness are introduced, from which an iterative algorithm for designing the lifting scheme is presented 相似文献
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Two-dimensional orthogonal wavelets with vanishing moments 总被引:4,自引:0,他引:4
We investigate a very general subset of 2-D, orthogonal, compactly supported wavelets. This subset includes all the wavelets with a corresponding wavelet (polyphase) matrix that can be factored as a product of factors of degree-1 in one variable. In this paper, we consider, in particular, wavelets with vanishing moments. The number of vanishing moments that can be achieved increases with the increase in the McMillan degrees of the wavelet matrix. We design wavelets with the maximal number of vanishing moments for given McMillan degrees by solving a set of nonlinear constraints on the free parameters defining the wavelet matrix and discuss their relation to regular, smooth wavelets. Design examples are given for two fundamental sampling schemes: the quincunx and the four-band separable sampling. The relation of the wavelets to the well-known 1-D Daubechies wavelets with vanishing moments is discussed 相似文献
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本文利用非线性随机微分方程来合成间歇混沌信号,针对该信号表现出的1/f噪声特征,在不同消失矩的小波基下进行相关特性分析.仿真结果发现,在功率谱的中间频段内,该信号的功率谱密度表现出典型的1/f噪声特性,其小波变换系数方差与相应的小波尺度呈对数线性关系;且在该频段内,部分尺度下该间歇性信号的小波变换系数的相关性随小波基的消失矩的增大而减小,在另一部分尺度下该相关性则随着消失矩的增大而增大.实验结果表明,随小波消失矩的增大,并非在所有尺度下小波变换对该间歇性信号均具有去相关作用.论文讨论了小波变换系数的方差和尺度的关系,详细分析了小波变换系数的相关性随小波消失矩的变化趋势. 相似文献
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The behavior of linear phase wavelet transforms in low bit-rate image coding is investigated. The influence of certain characteristics of these transforms such as regularity, number of vanishing moments, filter length, coding gain, frequency selectivity, and the shape of the wavelets on the coding performance is analyzed. The wavelet transforms performance is assessed based on a first-order Markov source and on the image quality, using subjective tests. More than 20 wavelet transforms of a test image were coded with a product code lattice quantizer with the image quality rated by different viewers. The results show that, as long as the wavelet transforms perform reasonably well, features like regularity and number of vanishing moments do not have any important impact on final image quality. The influence of the coding gain by itself is also small. On the other hand, the shape of the synthesis wavelet, which determines the visibility of coding errors on reconstructed images, is very important. Analysis of the data obtained strongly suggests that the design of good wavelet transforms for low bit-rate image coding should take into account chiefly the shape of the synthesis wavelet and, to a lesser extent, the coding. 相似文献