Very high resolution inverse synthetic aperture radar (ISAR) imaging of maneuvering targets is a complicated task. Due to the phase error caused by target's non-cooperative motion, we can't use conventional Fourier transform in ISAR imaging reconstruction. Therefore, the method of Range Instantaneous Doppler (RID) technique based on Fractional Fourier Transform (FRFT) is presented. First, we define a model of the ISAR received signal that is valid for maneuvering targets. In order to eliminate phase error caused by translational motion components, the strong scatter signal that backscattering from the target is used for phase compensation, which can be extracted from the echoes using FRFT. Finally, RID is proposed to reconstruct ISAR image. After time-frequency transform named SPWVD, we get the instantaneous Doppler frequency. Even without exact motion compensation, a clear image of the target, such as aircraft, is obtained, which avoids the insufficiency of conventional Fourier-based image algorithm. The theoretical analysis is validated by presenting and discussing the simulation results.
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