A Doppler parameters estimation technique for squint SAR imaging

An essential part of SAR processing is the estimation of the Doppler parameters of the received data-the Doppler centroid and the Doppler frequency rate. This paper proposes a Doppler parameters estimation technique for squint SAR imaging, where the estimation of the Doppler frequency rate is dependent on that of the Doppler centroid. It estimates the Doppler centroid based on the relationship of the Doppler centroid and the range cell migration (RCM), and estimates the Doppler frequency rate using an improved Radon ambiguity transform (RAT) method based on the data aligned according to the RCM trajectory. This technique needs no prior knowledge of the radar platform velocity and the beam squint angle, and shows good performance of estimating the Doppler parameters. Simulation results demonstrate the validity of the method.