A Doppler centroid estimation method using the Radon transform for forward-squint SAR imaging

For forward-squint synthetic aperture radar (SAR) imaging, the determination of the Doppler centroid is indispensable. With an analysis of the characteristics of the range cell migration in forward-squint mode, a Doppler centroid estimation technique is proposed, which utilizes the Radon transform to extract the skew angle information from the shape of the target response in the range-compressed image and then calculates the Doppler centroid. It can also resolve the Doppler ambiguity without the prior knowledge of the radar platform velocity and the beam squint angle, as is especially usable to forward-squint SAR. In addition, when the radar platform velocity is known, the beam squint angle can be also estimated. Simulation results demonstrate the validity of the method.