Inverse Synthetic Aperture Ladar Imaging Algorithm for Space Maneuvering Target Using Synchrosqueezing Short-time Fourier Transform

When imaging maneuvering target with Inverse Synthetic Aperture Ladar (ISAL), Doppler frequency time-variation exist in the echo signal in azimuth direction, which leads to azimuth unfocusing. The traditional time-frequency analysis method is difficult to meet the high precision imaging requirement for space maneuvering target because of its poor time-frequency resolution and the shortcoming of cross term. To solve these problems, a ISAL imaging algorithm based on Synchrosqueezing Short-Time Fourier Transform (SSSTFT) is proposed in this paper. For the space maneuvering target which approximately meets the uniformly accelerated motion in a short time, after the motion compensation, the range unit echo signal is modeled as a multicomponent polynomial phase signal. The SS-STFT is used to complete the time frequency imaging of multicomponent signals. Then the ISAL image of the space target can be obtained by taking the Doppler slices of different azimuth times. This method has high time frequency resolution and low computational complexity, which can be used for real-time calculation and low requirement for input signal parameters. It satisfies the imaging requirements of ISAL better. The effectiveness of the proposed method is verified by the simulation experiment of the space shuttle model.