On the use of joint time-frequency representations in SAR signal processing

The aim of this paper is to show that some of the open problems in Synthetic Aperture Radar signal processing can be seen in a new and advantageous perspective if the received signals are represented in the time-frequency domain. The joint time-frequency representation makes easier the extraction of the information necessary for the formation of the synthetic aperture, responsible for the high cross-range resolution. The proposed approach is applied to the imaging of moving objects and to the focusing of extended scenes, in presence of instabilities of the radar platform such that the conventional estimation techniques become insufficient. In particular, the time-frequency analysis allows the estimation of the useful signal parameters even in case of undersampling. This allows the use of relatively low Pulse Repetition Frequencies (PRF), avoiding then the shortcomings due to high PRFs, like the reduction of the sizes of the monitorable areas or the data rate increase.