ISAR Imaging of Nonuniformly Rotating Targets Based on Generalized Decoupling Technique

For nonuniformly rotating targets, such as targets with complex motions and nonsevere maneuvering targets, the range migration and the time-varying Doppler frequency deteriorate inverse synthetic aperture radar (ISAR) image reconstructed with the conventional range-Doppler (RD) algorithm. In this paper, we focus on the scatterer-dependent Doppler spread compensation and present an efficient ISAR imaging algorithm for nonuniformly rotating targets by employing the symmetric parametric instantaneous autocorrelation function (SPIAF) and the generalized decoupling technique (GDT). It belongs to the range-instantaneous-Doppler (RID) technique and can be easily implemented by using the complex multiplication, the fast Fourier transform (FFT) and the nonuniform FFT (NUFFT). The implementation, the cross-term, the computational cost, and the antinoise performance are analyzed for the GDT-based ISAR imaging algorithm. With the synthetic data and the real radar data, comparisons with other three representative ISAR imaging algorithms demonstrate that the GDT-based ISAR imaging algorithm can acquire a higher antinoise performance and a better cross-term suppression with a moderate computational cost. In addition, with discussions of the characteristics, the generalities and the implementation methods for the SPIAF and the GDT, we indicate that these two new techniques may be applied in more realistic applications.