Unambiguous doppler centroid estimation approach for synthetic aperture radar data based upon compressed signal magnitude

A new approach to Doppler ambiguity resolution is presented. This approach adopts the fact that the absolute Doppler centroid is a linear function of range frequency. Based on this concept, an alternative azimuth compression method that is without a prior knowledge about the motion parameters is developed and carried out in range frequency domain to accumulate the target energy along the azimuth. The resulting trajectories become straight lines with the same slope proportional to the unwrapped Doppler centroid. This slope can be well estimated by the azimuth cell walk correction/integration method. Two sets of measured synthetic aperture radar data (airborne and spaceborne radar) show that this approach works well in medium- and high-contrast scenes.