AUTO-FOCUSING CORRECTION FOR ROTATIONAL ACCELERATION EFFECTS ON INVERSE SYNTHETIC APERTURE RADAR IMAGES

摘要

Inverse synthetic aperture radar imaging systemsthat are used to image targets that undergo rotationalaccelerations are enhanced by signal processingtechniques which provide correction factors to reduce thefrequency-shift and frequency-stretch errors that occurdue to such accelerations. A target scan is subdividedinto a number of sub-apertures and a Fast FourierTransfer (FFT) is performed on the data for each sub-aperture to provide associated frequency sub-images. TheFFT is then subdivided in "sub-swaths" of amplitudeversus frequency for a plurality of frequency bands. Thechange-of-frequency, or frequency shift, data betweenprominent scattering points of each sub-image areprocessed to provide a phase correction factor thatincorporates range changes and translational accelerationdistortions for additional scattering points other thanthe most prominent scattering point. A frequency-stretchcorrection factor that compensates for rotationalacceleration distortion is also provided.