Based on the theory of exponential sums an d quadratic forms over finite field, the crosscorrelation function values betwee n two maximal linear recursive sequences are determined under some conditions.
Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation me...Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the Poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the Poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.展开更多
当窄带外辐射源数目稀少且空间分布不均匀时,通常会在无源雷达成像中产生稀疏的无规则空间谱填充,使得传统快速逆傅里叶方法(inverse fast Fourier transform,IFFT)或极坐标方法难以获得良好的目标成像效果。针对这种空间谱填充的稀疏...当窄带外辐射源数目稀少且空间分布不均匀时,通常会在无源雷达成像中产生稀疏的无规则空间谱填充,使得传统快速逆傅里叶方法(inverse fast Fourier transform,IFFT)或极坐标方法难以获得良好的目标成像效果。针对这种空间谱填充的稀疏性和非均匀性,利用压缩感知理论在处理稀疏随机采样信号重构问题上的优势,提出了稀疏无源雷达成像方法。同时通过构造传感矩阵的互相关和积累相关函数,对目标图像的可重构性进行了分析。理论分析和仿真结果表明,对具有稀疏随机空间谱特点的无源雷达成像,本文提出的成像方法是有效的。展开更多
文摘Based on the theory of exponential sums an d quadratic forms over finite field, the crosscorrelation function values betwee n two maximal linear recursive sequences are determined under some conditions.
基金supported by the National Natural Science Foundation of China(No.41174087,41204089)the National Oil and Gas Major Project(No.2011ZX05005-005)
文摘Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the Poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the Poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.
文摘当窄带外辐射源数目稀少且空间分布不均匀时,通常会在无源雷达成像中产生稀疏的无规则空间谱填充,使得传统快速逆傅里叶方法(inverse fast Fourier transform,IFFT)或极坐标方法难以获得良好的目标成像效果。针对这种空间谱填充的稀疏性和非均匀性,利用压缩感知理论在处理稀疏随机采样信号重构问题上的优势,提出了稀疏无源雷达成像方法。同时通过构造传感矩阵的互相关和积累相关函数,对目标图像的可重构性进行了分析。理论分析和仿真结果表明,对具有稀疏随机空间谱特点的无源雷达成像,本文提出的成像方法是有效的。
