分布式卫星多相位中心SAR-GMTI技术研究

发布时间：2018-11-14 19:23

【摘要】：合成孔径雷达（SAR）技术与地面运动目标检测（GMTI）技术相结合，可以在获得高分辨地面场景图像的同时完成地面动目标的检测及测速定位，具有重要的民用和军用价值。相比单通道SAR系统，多通道SAR的优势在于可以利用多个方位自由度有效的抑制主瓣杂波，改善动目标的检测性能，因而受到各国学者的广泛关注。本文针对分布式卫星多相位中心SAR实现GMTI功能，开展了关于沿航迹基线形式确定、时变混合基线预处理、与高分辨率宽测绘带成像兼容设计、模糊杂波抑制以及对误差稳健的动目标参数估计等关键技术研究。主要内容包括： 1、分析了多通道SAR系统中多个相位中心之间可能存在的时空关系，以交替收发模式为例，建立了多通道动目标信号模型。通过理论推导明确了形成GMTI基线的必备条件，得到如下结论：不同时间处于不同方位的两个相位中心之间的沿航迹基线，等于以同一时间基准对这两个相位中心位置进行插值后得到的等效位置之间的沿航迹差。该结论为不同通道构成方式下沿航迹基线的确定提供了依据。通过对比同一系统采用不同天线孔径划分和交替收发方式下的GMTI性能，说明了合理选择天线孔径划分和交替方式对提升GMTI性能的重要性。 2、提出了分布式卫星SAR-GMTI系统时变、混合基线的预处理方法。针对分布式卫星系统中星间基线时变导致SAR图像对相干性下降的问题，从分布式卫星SAR系统的观测几何构型出发，采用总体最小二乘法拟合航迹方程，并依据方程参数重构虚拟的新平行航迹。通过补偿原航迹和新航迹上的观测波程差，获得等效的固定基线回波数据。在此基础上，针对分布式卫星SAR系统中混合基线和雷达斜视导致沿航迹基线难以精确计算的问题，推导了存在混合基线和斜视情况下沿航迹基线的计算公式，提出了基于星历和回波数据的沿航迹基线计算方法。仿真实验结果表明，时变基线补偿后，能有效提高动目标检测性能；用所提方法计算得到的沿航迹基线长度作为测速定位的基线参数，可以获得高精度的测速定位结果。 3、采用方位多通道抑制多普勒模糊是实现高分辨率宽测绘带（HRWS）成像的有效方式，如果这些自由度用于主瓣杂波抑制则可以实现GMTI功能。因此，在多通道SAR系统中，有望实现两种模式的兼容工作。但此时GMTI性能会受到方位降采样引起的多普勒模糊的影响。为分析这一影响，推导了存在多普勒模糊下的杂波和动目标的信号形式，给出了系统参数的设计考虑。结合盲速、空域模糊和动目标积累损失等因素，重点讨论了在多普勒模糊情况下，脉冲重复频率（PRF）对GMTI性能的影响，并给出了一个PRF的优化选择仿真示例。根据理论分析和仿真实验结果可以得到一个选择PRF的重要原则，，即应避免抑制模糊杂波的凹口因为空域模糊而折回至感兴趣速度区间。实测数据的处理结果验证了理论分析的正确性。 4、提出了多特征联合挑选样本的多通道SAR模糊杂波抑制方法。针对强弱对比明显的非均匀场景中模糊强杂波的抑制问题，分析推导了模糊杂波的多通道导向矢量，以邻近强陆地杂波的近岸水面区域为例，建立了SAR图像域多通道信号模型。以模糊杂波导向的推导结果和建立的模型为依据，联合模糊杂波的幅度/相位直方图统计特性和边缘检测挑选训练样本，并采用自适应匹配滤波方法抑制杂波。仿真实验验证了所提方法的有效性。 5、实际处理环境中，图像配准误差和通道相位误差不可避免，这将导致多通道SAR-GMTI处理时动目标径向速度估计和定位精度下降。针对这一问题，提出了基于自适应数据重构和子空间投影的动目标径向速度估计方法。在联合像素信号模型下，利用抑制杂波的维纳权矢量自适应重构包含动目标单元的多通道数据，再采用子空间投影算法从重构的包含动目标的单次快拍数据中估计动目标的径向速度。仿真实验和某机载多通道SAR-GMTI实测数据的处理结果验证了所提方法的有效性和稳健性。
[Abstract]:The combination of synthetic aperture radar (SAR) and ground motion target detection (GMTI) technology can be used to detect and position the ground moving target while obtaining the high-resolution ground scene image, which has important civilian and military value. Compared with the single-channel SAR system, the advantage of the multi-channel SAR is that a plurality of azimuth degrees of freedom can be used to effectively suppress the main lobe clutter and improve the detection performance of the moving target, so that the multi-channel SAR is widely concerned by the scholars of various countries. In this paper, the GMTI function is realized for the distributed satellite multi-phase center SAR, and the pre-processing of the time-varying mixed base line and the imaging compatibility with the high-resolution and wide-scale mapping tape are carried out. Research on the key technologies such as the fuzzy clutter suppression and the parameter estimation of moving target with robust error. The main contents include: 1. The time-space relationship between multiple phase centers in the multi-channel SAR system is analyzed, and the multi-channel dynamic target signal is set up in the alternate mode of transmission and reception. The necessary conditions for forming the GMTI base line are defined by the theory, and the following conclusions are obtained: along the track between two phase centers with different time in different directions baseline, equal to the edge between the equivalent positions resulting from the interpolation of the two phase center positions at the same time reference The conclusion is that the determination of the baseline of the track along the track is provided in the form of different channels. Based on the comparison of the GMTI performance of the same system with different antenna aperture and alternate receiving and receiving mode, this paper illustrates the rational choice of the antenna aperture division and the alternative way to the improvement of the GMTI performance. in that case of a distributed satellite SAR-GMTI system, a time-varying, hybrid baseline of a distributed satellite SAR-GMTI system is propose. Based on the observation geometry of the distributed satellite SAR system, the overall least square method is used to fit the track equation and the virtual is reconstructed according to the equation parameters. the new parallel track is obtained, and the equivalent fixed base is obtained by compensating the difference of the observed wave path on the original track and the new track. On the basis of this, the problem that the baseline and strabismus in the distributed satellite SAR system is difficult to calculate accurately along the track baseline is derived, and the baseline and strabismus are derived from the baseline and the strabismus. Based on the calculation formula of the ephemeris and the echo data along the track basis, The simulation results show that the dynamic target detection performance can be effectively improved after the time-varying baseline compensation, and the measured baseline length along the track is used as the baseline parameter of the speed-measuring and positioning, and the high-precision measurement can be obtained. Fast positioning results. 3. The use of directional multi-channel suppression of Doppler ambiguity is an effective way to achieve high resolution wide-scale mapping (HRWS) imaging. If these degrees of freedom are used for main lobe clutter suppression, The GMTI function is realized. Therefore, in the multi-channel SAR system, it is expected to implement two functions The compatibility of the mode is compatible. However, the GMTI performance is caused by the orientation drop sampling The influence of the Doppler ambiguity is analyzed. In order to analyze the influence, the signal form of the clutter and the moving target in the presence of the Doppler ambiguity is derived. In this paper, the influence of pulse repetition frequency (PRF) on the performance of GMTI in the case of Doppler ambiguity and the effect of pulse repetition frequency (PRF) on the performance of GMTI are discussed, and a PRF is given. According to the theoretical analysis and the simulation experiment results, an important principle to choose the PRF is obtained, that is, the notch of the fuzzy clutter should be avoided because the airspace is fuzzy and folded back to the region of interest. The processed results of the measured data are verified. Correctness of the theoretical analysis. In view of the problem of the suppression of the fuzzy strong clutter in the non-uniform scene with the strong or weak contrast, the multi-channel guide vector of the fuzzy clutter is derived, and the SA is established in the near-shore surface area of the strong land clutter. The R-image domain multi-channel signal model is based on the derived result of the fuzzy clutter guidance and the established model, and the training samples for the amplitude/ phase histogram statistics of the combined fuzzy clutter and the edge detection are selected, and the self-adapting is adopted. The filter method should be matched to suppress the clutter. The simulation experiment The validity of the proposed method is verified. 5. In the actual processing environment, the image alignment error and the channel phase error are inevitable, which will result in the multi-channel SAR-GMTI processing. In this paper, the self-adaptive data reconstruction and subspace are proposed for this problem. The invention relates to a method for estimating a moving target radial velocity of a projection, Estimation of the radial velocity of the moving target in the beat data. The simulation experiment and the processing results of the measured data of a certain airborne multi-channel SAR-GMTI
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN958

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