现代谱估计方法能够反演基于几何绕射理论(geometric theory of diffraction,GTD)的模型参数,但不能处理非均匀不完备的雷达散射截面(radar cross section,RCS)数据。此外,通过暗室测量获取完备的RCS数据也需要较大的时空开销。针对上...现代谱估计方法能够反演基于几何绕射理论(geometric theory of diffraction,GTD)的模型参数,但不能处理非均匀不完备的雷达散射截面(radar cross section,RCS)数据。此外,通过暗室测量获取完备的RCS数据也需要较大的时空开销。针对上述问题,提出一种基于迭代加权最小二乘(iteratively reweighed least squares,IRLS)的跳频模式下GTD散射参数提取和RCS重构方法。该方法将稀疏重构理论与GTD散射模型相结合,能够在RCS数据非均匀不完备的条件下反演散射参数和实现RCS重构。仿真数据和电磁计算数据用于验证所提方法的有效性,实验结果表明该方法对降低暗室步进频率RCS的测量成本和扩增雷达RCS数据具有重要意义。展开更多
为解决经典PSInSAR技术在非城区因受永久散射体空间分布不足而导致地形形变监测误差较大的问题,提出基于分时散射体(partial time scatterer,PTS)提取的改进算法。首先基于改进的经验模态分解对影像进行边缘保持平滑滤波降噪,然后采用...为解决经典PSInSAR技术在非城区因受永久散射体空间分布不足而导致地形形变监测误差较大的问题,提出基于分时散射体(partial time scatterer,PTS)提取的改进算法。首先基于改进的经验模态分解对影像进行边缘保持平滑滤波降噪,然后采用可信概率估计对PTS目标进行联合提取,最后通过参数差分估计分离PTS相位和计算形变速率,从而得到监测区的地表形变。实验结果表明,提取的PTS目标基本可保持传统PS点的空间分布特性和时序变化趋势,提高非城区目标点的空间分布密度,本文算法具有有效性。展开更多
The extraction of the weakly excited anti-symmetric Lamb wave from a submerged thin spherical shell backscattering is very difficult if the carrier frequency of the incident short tone burst is not at its frequency of...The extraction of the weakly excited anti-symmetric Lamb wave from a submerged thin spherical shell backscattering is very difficult if the carrier frequency of the incident short tone burst is not at its frequency of greatest enhancement. Based on a single channel iterative time reversal technique, a method for isolating the subsonic anti-symmetric Lamb wave is proposed in this paper. The approach does not depend on the form function of a thin shell and any other priori knowledge, and it is also robust in the presence of some stochastic noise. Both theoretical and numerical results show that the subsonic anti-symmetric Lamb wave can be identified, even when the carrier frequency of the incident short tone burst is away from the frequency of greatest enhancement. The phenomenon may also be observed even in the case that the subsonic anti-symmetric Lamb wave is submerged in the noise, other than the case with the Signal to Noise Ratio being less than 10 d B, when the amplitude of the noise is comparable with the specular wave. In this paper, each iteration process contains a traditional transmission and time reversal transmission steps. The two steps can automatically compensate the time delay of the subsonic anti-symmetric Lamb wave relative to the specular wave and within-mode dispersion in the forward wave propagation.展开更多
在大的目标观测视角下,为抑制散射中心的越分辨单元徙动影响,获得高质量的逆合成孔径雷达(ISAR)目标成像结果,不仅需要目标的相对转动信息,而且需要估计其等效旋转中心。该文通过等分目标回波获取2幅距离-D opp ler图像,并在图像域跟踪...在大的目标观测视角下,为抑制散射中心的越分辨单元徙动影响,获得高质量的逆合成孔径雷达(ISAR)目标成像结果,不仅需要目标的相对转动信息,而且需要估计其等效旋转中心。该文通过等分目标回波获取2幅距离-D opp ler图像,并在图像域跟踪3个散射中心的位置变化信息,提出了一种目标转速和等效旋转中心联合估计方法。同时,分析了若干影响该方法性能的因素,为方法的正确实施提供了指导。数值仿真实验表明了等效旋转中心估计的必要性和本方法的有效性。展开更多
文摘现代谱估计方法能够反演基于几何绕射理论(geometric theory of diffraction,GTD)的模型参数,但不能处理非均匀不完备的雷达散射截面(radar cross section,RCS)数据。此外,通过暗室测量获取完备的RCS数据也需要较大的时空开销。针对上述问题,提出一种基于迭代加权最小二乘(iteratively reweighed least squares,IRLS)的跳频模式下GTD散射参数提取和RCS重构方法。该方法将稀疏重构理论与GTD散射模型相结合,能够在RCS数据非均匀不完备的条件下反演散射参数和实现RCS重构。仿真数据和电磁计算数据用于验证所提方法的有效性,实验结果表明该方法对降低暗室步进频率RCS的测量成本和扩增雷达RCS数据具有重要意义。
文摘为解决经典PSInSAR技术在非城区因受永久散射体空间分布不足而导致地形形变监测误差较大的问题,提出基于分时散射体(partial time scatterer,PTS)提取的改进算法。首先基于改进的经验模态分解对影像进行边缘保持平滑滤波降噪,然后采用可信概率估计对PTS目标进行联合提取,最后通过参数差分估计分离PTS相位和计算形变速率,从而得到监测区的地表形变。实验结果表明,提取的PTS目标基本可保持传统PS点的空间分布特性和时序变化趋势,提高非城区目标点的空间分布密度,本文算法具有有效性。
基金supported by the National Natural Science Foundation of China (46976019)the open project of the State Key Laboratory of Acoustics, Chinese Academy of Sciences (SKLA201202)
文摘The extraction of the weakly excited anti-symmetric Lamb wave from a submerged thin spherical shell backscattering is very difficult if the carrier frequency of the incident short tone burst is not at its frequency of greatest enhancement. Based on a single channel iterative time reversal technique, a method for isolating the subsonic anti-symmetric Lamb wave is proposed in this paper. The approach does not depend on the form function of a thin shell and any other priori knowledge, and it is also robust in the presence of some stochastic noise. Both theoretical and numerical results show that the subsonic anti-symmetric Lamb wave can be identified, even when the carrier frequency of the incident short tone burst is away from the frequency of greatest enhancement. The phenomenon may also be observed even in the case that the subsonic anti-symmetric Lamb wave is submerged in the noise, other than the case with the Signal to Noise Ratio being less than 10 d B, when the amplitude of the noise is comparable with the specular wave. In this paper, each iteration process contains a traditional transmission and time reversal transmission steps. The two steps can automatically compensate the time delay of the subsonic anti-symmetric Lamb wave relative to the specular wave and within-mode dispersion in the forward wave propagation.
文摘在大的目标观测视角下,为抑制散射中心的越分辨单元徙动影响,获得高质量的逆合成孔径雷达(ISAR)目标成像结果,不仅需要目标的相对转动信息,而且需要估计其等效旋转中心。该文通过等分目标回波获取2幅距离-D opp ler图像,并在图像域跟踪3个散射中心的位置变化信息,提出了一种目标转速和等效旋转中心联合估计方法。同时,分析了若干影响该方法性能的因素,为方法的正确实施提供了指导。数值仿真实验表明了等效旋转中心估计的必要性和本方法的有效性。
