Subaperture autofocus for synthetic aperture radar
Abstract
A subaperture autofocus algorithm for synthetic aperture radar (SAR) partitions rangecompressed phasehistory data collected over a full aperture into equalwidth subapertures. Application of a onedimensional Fourier transform to each range bin converts each subaperture data set into a fullscene image (map). Any linear phase difference, or phase ramp, between a pair of subapertures expresses itself as crossrange drift in their maps. A traditional autofocus algorithm fits a polynomial to inferred equal width phase ramps. If the true phase error function contains significant highorder components, then polynomial regression generates a poor estimate of the phase error function. Instead of fitting a polynomial, we fit a sinusoidal function through the inferred phase ramps.
 Publication:

IEEE Transactions on Aerospace Electronic Systems
 Pub Date:
 April 1994
 DOI:
 10.1109/7.272285
 Bibcode:
 1994ITAES..30..617C
 Keywords:

 Data Compression;
 Error Functions;
 Focusing;
 Image Processing;
 Image Resolution;
 Phase Error;
 Synthetic Aperture Radar;
 Algorithms;
 Fourier Transformation;
 Polynomials;
 Sine Waves;
 Communications and Radar