A novel high-order sinusoidal trajectory deviation compensation approach

In unman aero vehicle (UAV) synthetic aperture radar (SAR), serious high-order sinusoidal trajectory deviation is induced due to the instability of the platform. The phase error induced by the trajectory deviation produces spectral replicas of the azimuth signal, which are shifted in the range direction after range cell migration correction (RCMC) in the range doppler domain. It is extremely difficult to estimate the phase error which induces the spectral replicas by the phase gradient autofocus algorithm (PGA). In this paper, a novel high-order sinusoidal trajectory deviation compensation approach is proposed. The raw data are divided into small subapertures and range walk correction (RWC) is performed in the azimuth-time domain to avoid the range shift of the spectral replicas. Additionally, range resolution reduction is performed to assure the estimation accuracy of PGA. After PGA, the estimations for each sub-aperture are recombined and then the data are processed again with the updated motion deviations. The validity of the proposed approach is demonstrated by computer simulations and experiments based on real data.