3-D Squint InISAR Imaging Technique for Maneuvering Ship Targets under Nonorthogonal Baseline Configuration via the Joint Distortion Correction

Interferometric inverse synthetic aperture radar (InISAR) imaging technology can achieve the three-dimensional (3-D) reconstruction of ship targets, which can provide additional features for the marine target recognition. However, the complex 3-D rotations of ship targets in the presence of a high sea state pose significant challenges for the high-resolution imaging procedure. In addition, the current research on 3-D squint InISAR imaging with nonorthogonal baselines remains obvious limited. To overcome these issues, a 3-D squint InISAR imaging technique is proposed for maneuvering targets under the nonorthogonal baseline configurations via the joint distortion correction method, which consists of two stages. First, we propose a parameter estimation algorithm that combines the local polynomial ambiguity function with the velocity-adjustable and self-adaptive particle swarm optimization. This algorithm achieves equivalent parameter estimation accuracy with less computational complexity while preserving the phase information. Second, the joint distortion correction method is employed to achieve a distortion-free 3-D imaging result. It includes the phase compensation method (APCM) and coordinate remapping method, which are utilized to correct the distortion caused by squint and the nonorthogonal baselines. Furthermore, a principle is provided for selecting the baseline length in the InISAR system to ensure the technology's effective implementation. Simulation and field experiments are conducted to verify the effectiveness of this proposed algorithm.