Inverse Synthetic Aperture Radar Imaging of Nonuniformly Rotating Target Based on the Parameters Estimation of Multicomponent Quadratic Frequency-Modulated Signals

Inverse synthetic aperture radar (ISAR) is very useful in radar signature applications. In ISAR imaging of nonuniformly rotating target, the radar echo signal in a range cell can be modeled as multicomponent quadratic frequency-modulated (QFM) signals. The high-quality radar images can be obtained by the parameters estimation of QFM signals combined with the range-instantaneous-Doppler technique. In this paper, a novel algorithm for the parameters estimation of QFM signal via the modified cubic phase function (MCPF) is presented. This algorithm estimates the quadratic phase coefficient at first, and the other parameters can be estimated by the traditional CPF and the fast Fourier transform. The implementation of MCPF algorithm requires only 1-D maximizations, and the comparison with some existing algorithms is discussed. The ISAR imaging results of simulated and raw data validate the effectiveness of the novel algorithm proposed in this paper.