SYNTHETIC APERTURE RADAR SYSTEM HAVING A THIRD ORDER TUNED AUTO COMPENSATOR FOR RESIDUAL ANTENNA MOTION AND METHOD FOR ITS USE

In a SAR system a method is provided for compensating for antenna residual motion relative to a motion sensor, wherein such residual motion causes phase corruption in a radar image produced by the SAR system. Residual motion compensation is provided by first correlating a received radar signal to a range line having a plurality of azimuth positions. Such signal is transformed into a frequency spectrum indicating the reflectivity of point reflectors at the various azimuth positions. Then, the range line is sampled for symmetric sets of sequential point reflectors positioned along the range line at a consecutive distance from each other corresponding to a specified frequency associated to a mode of residual vibration of the antenna. The amplitude and phase angle of said mode of the antenna residual motion may be obtained from such symmetric sets.