ISAR imaging of target with complex motion associated with the fractional Fourier transform

High-resolution inverse synthetic aperture radar (ISAR) imaging based on parameter estimation of polynomial phase signal is a quite significant research hotspot, in which the azimuth echo can be modeled as multi-component quadratic frequency modulation (QFM) signal after preprocessing, which leads to the time-varying Doppler frequency. In this paper, an effective parameter estimation method called the product form of symmetric correlation function based on the fractional Fourier transform (PFrSCF) is proposed. In proposed method, a novel symmetric correlation function is used to reduce phase order of QFM signal firstly. Then, the PFrSCF can estimate two parameters of QFM signal simultaneously by the fractional Fourier transform and suppress cross term by the product in fractional Fourier transform domain. Compared with other methods, the PFrSCF is capable of suppressing cross term effectively and ensuring the good accuracy of parameters. Moreover, the PFrSCF is robust in noisy environment. Finally, associated with range-instantaneous-Doppler imaging technology, a novel ISAR imaging algorithm is presented based on PFrSCF method. The performances of PFrSCF method and the corresponding ISAR imaging algorithm of target are verified by simulated and real data.