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1.
通过仿真实验,对相干法和非相干法两种宽带高分辨波束形成的方法在性能上进行了比较。非相干法原理简单,易于实现,不需要对方位进行预估,但其分辨性能不如相干法,尤其是在当目标为相干信号时,非相干信号子空间法失效;相干法无论目标是否相干,均具有良好的分辨性能,特别是在低信噪比的条件下仍有一定的分辨能力。但是,它需要预估方位,当预估方位的误差较大时,相干法的性能急剧下降。  相似文献   

2.
梁国龙  张柯  王逸林  范展 《声学技术》2013,32(6):464-468
基于声矢量阵的质点速度场平滑(ParticleVelocityFieldSmoothing,PVFS)算法是一种有效的解相干算法,但是当存在大量相干源时,该算法性能急剧下降甚至失效。在PVFS算法的基础上,提出了矩阵平方平滑(MatrixSquareSmoothing,MSS)-PVFS算法,该算法是对PVFS算法的改进,通过对PVFS算法构造的数据协方差矩阵进行平方、矩阵分块以及矩阵块间交叉相乘等数学运算,增强了PVFS算法解相干的能力,并大大增加了其分辨相干源的数目。计算机仿真结果表明,MSS—PVFS算法的效果与空间平滑(SpatialSmoothing,SS)-PVFS算法大致相同,但在低信噪比条件下,该方法具有更高的DOA估计精度。  相似文献   

3.
声矢量阵列的求根MUSIC算法及其性能分析   总被引:1,自引:0,他引:1  
在传统声压传感器阵列的求根MUSIC算法的基础上,提出了基于矢量传感器阵列的求根MUSIC算法及其修正形式,通过接收阵列信号的空间谱,选择合适的引导方位,可实现声源的波达方向(DOA)估计.理论推导和仿真实验表明,采用均匀矢量传感器线性阵列的求根MUSIC算法在低信噪比、小快拍数情况下的估计性能要优于传统声压传感器阵列的求根MUSIC算法,同时该算法的计算量远远小于矢量传感器列的MUSIC算法.  相似文献   

4.
针对正交匹配追踪(Orthogonal Matching Pursuit, OMP)算法在实际的波达方向(Direction of Arrival, DOA)估计应用中,测向分辨率较低且在相干信号环境下估计性能较差的问题,提出了一种虚拟阵列空间平滑DOA估计算法.以互质阵列为模型,通过在正交匹配追踪算法重构信号的基础上,使用虚拟内插的方法,构造均匀虚拟阵列,能够提高波达方向的估计精度,加入空间平滑算法,可以分辨相干信号.仿真结果表明,使用虚拟内插算法之后,空间谱图波峰更尖锐,且在信噪比为0 dB时,最高探测精度提高到2°,测向分辨率明显有所提升,同时加入空间平滑算法,可以有效地分辨相干信号,且在信噪比为0 dB时,最高探测精度提高为4.7°,验证了本文方法的有效性.  相似文献   

5.
虞飞  宋俊  余赟  苏冰 《声学技术》2023,42(5):649-654
通过稀疏重构得到传感器阵列输出数据的稀疏表示模型,研究了单快拍采样情形下的信号到达角(Direction of Arrival, DOA)估计问题。提出了一种基于最小均方误差(Minimum Mean-Square Error, MMSE)准则迭代实现的单快拍到达角估计算法(Iterative Implementation of MMSE, II-MMSE)。该算法将原有的稀疏表示模型中稀疏信号矢量的求解问题,转化为迭代求解稀疏功率对角阵,进而估计多目标信号的DOA。给出了算法的完整实现流程,从理论上分析了II-MMSE算法的迭代收敛性和对阵列模型误差的鲁棒性。仿真结果表明,II-MMSE算法在低信噪比、相干背景、小样本、阵列未校准等条件下都具有良好的测向精度和多目标分辨能力。  相似文献   

6.
研究了基于分类矢量量化技术的超声数据压缩算法,提出了基于峰值数的超声数据分类方法以及基于峰值距离失真测度的码字搜索算法。本文提出的算法充分利用了超声信号的特征,能够很好地保存超声信号的峰值信息。实验表明,相对于普通矢量量化器,本文提出的分类矢量量化器能够在保持相同压缩比的情况下提高重构信号的信噪比。将此矢量量化器与霍夫曼编码相结合,其压缩比可达1:50,高于基于小波变换的压缩算法。  相似文献   

7.
李海森  李珊  周天   《振动与冲击》2014,33(4):138-142
在多波束测深声呐的工作环境中,若海底反向散射信号不满足点源假设,方位估计精度将严重下降,而基于分布源模型的方位估计算法可以适应这种环境。目前,大多数分布源算法要求分布源之间不相干,有人提出采用Toeplitz方法估计相干分布源,但该方法精度不高并且忽略了角度扩展参数。为解决多波束测深声呐相干分布源的方位估计问题,提出了基于空间平滑的广义MUSIC方法,公式推导证明了算法的有效性,通过计算机仿真给出算法方位估计的精度以及不同信噪比条件下的性能,最后采用多波束测深系统的实验数据对算法进行了验证。  相似文献   

8.
相干分布源的方位估计   总被引:1,自引:0,他引:1       下载免费PDF全文
马培锋  严胜刚 《声学技术》2007,26(5):817-821
在水下声纳工作的环境中,若目标体沿中心角方向的扩展角度不能忽略,则基于点源假设的众多高分辨方位估计算法会导致错误的估计结果,而基于分布式目标模型的方位估计算法则可以适应这种目标环境。目前,随着空间分布源受到越来越多的关注,有人相继提出了一些算法例如DSPE和ESPRIT等等,但是这些算法需要很高的输入信噪比和要求不同目标源之间不相干,为了解决相干源的方位估计问题以及提高算法低信噪比下的估计性能,给出一种处理方法。仿真实验证明,该方法能够在低信噪比下提高算法的估计性能及有效的区分相干源。  相似文献   

9.
陈鹏  陈航 《声学技术》2004,23(Z1):124-127
采用最小模算法对于空间非相干信号有很好的分辨效果.本文详细地介绍了最小模方法的原理,并通过仿真指出了最小模算法对空间相干信号难以区分的缺点.为此本文提出了一种有效的解决方案,采用空间平滑处理来去除信号的空间相干效应,通过仿真证明了算法的有效性.  相似文献   

10.
声矢量传感器由声压传感器和质点振速传感器组成,可用在空间某点同步测量声场的声压和质点振速信息。但矢量传感器在实际制作时,可能存在声压传感器和质点振速传感器中心不一致的情况,即矢量声场的非共点测量。这会使得声压与振速通道之间的接收信号存在时延差,从而影响矢量传感器的定向性能。从理论上分析了时延差对平均声强法定向的影响,即降低了信号处理的信噪比及引入π相位的定向误差,并提出采用互相关声能流法进行定向。通过仿真分析了中心不一致、入射角度和信噪比等因素对不同类型的目标定向结果的影响,并验证和讨论了互相关声能流定向算法的有效性和适用性。  相似文献   

11.
For the first fime,the diagnosis idea based on a correlation integral is proposed,which re-gards the correlation integral as a feature set.The correlation dimension is contained in the double-log curve of the correlation integral to scale,so extracting features directly from the correlation integral can avoid the bottleneck problem of determining the range of non-scale length.Several features extracted from the correlation integral are better than the single feature of the correlation dimension when descri-bing the signal.It is obvious that this method utilizes more information of the signal than does the cor-relation dimension.The diagnosis examples verify that this method is more accurate and more effective.  相似文献   

12.
13.
Do DD  Kim N  An JW  Lee KY 《Applied optics》2004,43(23):4520-4526
An investigation of the effects of apodization on a holographic demultiplexer that is based on a photopolymer grating is presented. Uniform and Gaussian apodized gratings are fabricated in a DuPont HRF-150-38 photopolymer. From the theoretical and experimental results, the spectral response of the apodized grating has a larger main lobe but lower sidelobes than those in the uniform-grating case. A 42-channel demultiplexer that is based on the Gaussian apodized grating with an 0.4-nm channel spacing is demonstrated. A cross-talk level of -30 dB and an interchannel uniformity of 1.5 dB are archived in the wavelength range of approximately 1550 nm.  相似文献   

14.
Reversible and irreversible changes in magnetization due to stress on a minor hysteresis loop were studied at various magnetic field strengths. It was found that the irreversible changes were not always directed toward the principal anhysteretic, contrary to Jiles and Atherton's hypothesis (1986). Also, two different demagnetization methods were used within the minor loop to test the existence of postulated offset anhysteretic curves. The results of asymmetric demagnetizations seemed to support this suggestion  相似文献   

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Abstract

This book can and perhaps should be seen as a kind of portable exhibition with a wall label by Hilton Kramer. As an exhibition it should be reviewed in a fashion somewhat different from a book, with a much greater proportion of text. For many years Kertész's ‘distortions’ have been considered among the most successful surreal photographs ever made. Few people were aware that this series was as extensive as it turned out to be because many of the images had not been published or exhibited. Now that everything Kertész has done is being given the ‘master’ treatment, we are permitted to see what the photographer in earlier times would perhaps have left unseen.  相似文献   

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19.
A force acting on a nanoparticle occurring in a fluid has been studied by the molecular dynamics method. It is shown that this force is nonstationary and exhibits a relaxation character. At the initial instant, it is two to three times the Stokes force, but then decreases and, outside the first relaxation region, becomes smaller than the Stokes force. A stationary force acting on a nanoparticle is determined by the particle mass and size. Correlation expressions for determining the drag coefficient are constructed. It is established that the drag force is anisotropic.  相似文献   

20.
A mathematical model is presented for cyclic heat treatment of a film on a substrate, and heating curves have been constructed for a thin silicon wafer heated by an infrared source and cooled by forced convection.  相似文献   

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