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机动目标的复杂运动导致散射体回波信号多普勒频率时变,给ISAR成像方位向处理带来困难。现有的基于短时傅里叶变换,魏格纳分布,平滑魏格纳分布等瞬时成像算法由于受时频分辨率低或交叉项等因素影响,不适合机动目标的ISAR实时成像。针对这些问题,本文提出一种基于同步挤压变换(Synchrosqueezing Transformation,SST)的机动目标高分辨ISAR成像新方法。首先把平动补偿后的距离门回波信号建模为多成分多项式相位信号(polynomial phase signal,PPS),然后利用SST对多成分PPS进行时频分析,得到的回波信号时频分布具有高的时频聚集性且不带来任何交叉项,沿某一方位时刻取其切片得到机动目标的高分辨ISAR图像。最后,计算机仿真和实测数据验证了提出算法的有效性。
The complicated motion of the maneuvering target causes the time-varying Doppler frequency of the echo signal of the scatterer, which makes it difficult to solve the azimuth-oriented ISAR imaging. Existing instantaneous imaging algorithms based on short-time Fourier transform, Wigner distribution and smoothing Wigner distribution are not suitable for real-time ISAR imaging of maneuvering targets due to the influence of low time-frequency resolution or cross terms. To solve these problems, this paper presents a new method of high resolution ISAR imaging of maneuvering targets based on Synchrosqueezing Transformation (SST). Firstly, the translational compensated distance gate echo signal is modeled as a polynomial phase signal (PPS), and then the SST is used to perform time-frequency analysis on the multi-component PPS. The time-frequency distribution of the echo signal obtained is high The time-frequency congruence without any cross terms and high-resolution ISAR images of maneuvering targets are obtained by slicing them along a certain azimuth. Finally, computer simulation and measured data verify the effectiveness of the proposed algorithm.