An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are...An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are studied. The distribution of maximum amplitude and the evolution of time series and spectra during wave packet propagation and the variation of water surface parameters are extensively investigated. The results reveal that the characteristics of focusing waves are significantly influenced by wave directionality and that the breaking criteria for directional waves are distinctly different from those for unidirectional waves.展开更多
A robust weighted focusing matrix is proposed for CSM (Coherent Signal-Subspace Method). An explicit expression is deduced to estimate the SNR (Signal-to-Noise Ratio) by studying the characteristics of covariance matr...A robust weighted focusing matrix is proposed for CSM (Coherent Signal-Subspace Method). An explicit expression is deduced to estimate the SNR (Signal-to-Noise Ratio) by studying the characteristics of covariance matrices and then a weighted focusing matrix, which can improve the performance of the original CSM in application, is formed. The results of computer simulation, water tank experiment and ship noise data analysis show the efficiency of the method.展开更多
为了提升分布式传感器场景下对于宽带辐射源的定位效果,本文提出了一种基于到达时间差(Time Difference Of Arrival,TDOA)的多频率聚焦与融合的相干辐射源直接定位(Direct Position Determination,DPD)方法 .首先,对衰减系数未知的传感...为了提升分布式传感器场景下对于宽带辐射源的定位效果,本文提出了一种基于到达时间差(Time Difference Of Arrival,TDOA)的多频率聚焦与融合的相干辐射源直接定位(Direct Position Determination,DPD)方法 .首先,对衰减系数未知的传感器时域接收信号进行预处理,进行数据分段和频域变换,将宽带信号转化成若干个多快拍窄带频域信号;其次,根据最佳聚焦矩阵构造准则,构造聚焦矩阵,将各频率对应的信号聚焦到中心频率附近频谱能量最大的聚焦频率,得到聚焦后的接收数据;然后,根据子空间正交性建立关于辐射源位置的最小化代价函数,融合多个聚焦后的代价函数解决衰减系数未知的问题;最后,结合拉格朗日乘子法,通过网格点上代价函数值的谱峰搜索得到宽带辐射源的估计位置.所提方法可以在衰减系数未知的情况下实现相干辐射源的高精度定位,仿真和实际测试结果表明本文所提方法的有效性,在信噪比大于0 dB的四节点多径定位场景中,所提方法的定位性能较其他时差直接定位性能提升了30%以上.展开更多
基金This research was partially supported by the National Natural Science Foundation of China (Grant No. 50379002),the Korea Research Council of Public Science and Technology (Principal R&D Program) and Korea Ministry of Science and Technology (International Collaboration Research Program)
文摘An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are studied. The distribution of maximum amplitude and the evolution of time series and spectra during wave packet propagation and the variation of water surface parameters are extensively investigated. The results reveal that the characteristics of focusing waves are significantly influenced by wave directionality and that the breaking criteria for directional waves are distinctly different from those for unidirectional waves.
基金This work support by the National Natural Science Foundation of China and the National DefenseScience Foundation of China
文摘A robust weighted focusing matrix is proposed for CSM (Coherent Signal-Subspace Method). An explicit expression is deduced to estimate the SNR (Signal-to-Noise Ratio) by studying the characteristics of covariance matrices and then a weighted focusing matrix, which can improve the performance of the original CSM in application, is formed. The results of computer simulation, water tank experiment and ship noise data analysis show the efficiency of the method.
文摘为了提升分布式传感器场景下对于宽带辐射源的定位效果,本文提出了一种基于到达时间差(Time Difference Of Arrival,TDOA)的多频率聚焦与融合的相干辐射源直接定位(Direct Position Determination,DPD)方法 .首先,对衰减系数未知的传感器时域接收信号进行预处理,进行数据分段和频域变换,将宽带信号转化成若干个多快拍窄带频域信号;其次,根据最佳聚焦矩阵构造准则,构造聚焦矩阵,将各频率对应的信号聚焦到中心频率附近频谱能量最大的聚焦频率,得到聚焦后的接收数据;然后,根据子空间正交性建立关于辐射源位置的最小化代价函数,融合多个聚焦后的代价函数解决衰减系数未知的问题;最后,结合拉格朗日乘子法,通过网格点上代价函数值的谱峰搜索得到宽带辐射源的估计位置.所提方法可以在衰减系数未知的情况下实现相干辐射源的高精度定位,仿真和实际测试结果表明本文所提方法的有效性,在信噪比大于0 dB的四节点多径定位场景中,所提方法的定位性能较其他时差直接定位性能提升了30%以上.
文摘针对目前二元光学元件掩模制作工艺过程的诸多不足,对连续型平面衍射聚光透镜掩模的激光直写制作工艺进行了研究。基于基尔霍夫标量衍射理论,采用光线追迹法设计了连续型平面衍射聚光透镜掩模。采用激光直写技术,利用CLW S-300M/C极坐标激光直写设备、S1830光刻胶和M ICROPO S IT-351显影液,进行了刻写实验。实验表明,激光能量、预烘烤温度、显影液浓度以及预曝光对掩模微结构的制作均有影响。最后制作了掩模。与二元光学元件掩模的制作工艺相比,该技术具有工艺简单、制作周期短且易于操作的优点。
