ISAR Imaging of Precession Target Based on Joint Constraints of Low Rank and Sparsity of Tensor.

Precession is a typical form of micromotion that can bring about complex and time-varying Doppler modulation. The range instantaneous Doppler (RID) method, which uses time-frequency analysis instead of the Fourier transform to describe the time-varying Doppler, is typically used to obtain the high-resolution inverse synthetic aperture radar (ISAR) image of a precession target. However, the observation time of a specific target is often nonuniform due to various interference and channel switching among multichannel radars, which will lead to a sparse aperture. Sparse aperture can cause sidelobe interference in ISAR image obtained by the RID method, making it difficult to focus well. To solve the problem whereby the RID method fails to image a precession target with sparse aperture, this article proposes a new method based on the joint constraints of low-rank and sparsity of tensor and uses the alternating direction method of multipliers to solve the problem. The low rank can constrain the correlation among consecutive ISAR images, and sparsity can remove the impact of sparse aperture. This effectively eliminates the micro-Doppler interference and sidelobe interference in ISAR image and enables the reconstruction of precession target in a sequence of ISAR images with sparse aperture. Experimental results of simulations and darkroom measurements verify that the proposed method performs well on the ISAR images of conic precession target with sparse aperture.