Correction of the effects induced by the continuous motion in airborne FMCW SAR

The combination of frequency modulated continuous wave (FMCW) technology and synthetic aperture radar (SAR) leads to lightweight, cost-effective imaging sensors of high resolution. In FMCW SAR applications the conventional stop-and-go approximation used in pulse radar algorithms can be not valid anymore, therefore the motion within the sweep needs to be taken into account. Analytical development of the FMCW SAR signal model, starting from the deramped signal and without using the stop-and-go approximation, is presented in this paper. The model is then applied to spotlight and single transmitter/multiple receiver digital beam forming (DBF) operational mode, where the effect of the motion during the transmission and reception of the pulse, if not compensated for, can become seriously degrading for the SAR image quality. The derivation is then verified by processing real FMCW SAR data collected with the demonstrator system built at the Delft University of Technology.