Improved SAR imaging algorithm using FRFT

Improved Azimuth Compression with fractional fourier transform (FRFT) has been studied. Compared to using classic matched filtering technique, the image focused by FRFT has better resolutions. It has been founded that under the condition that chirp's bandwidth keeps the same, the longer pulse duration, the higher resolution of the signal after FRFT operation to this chirp. This paper applies FRFT to range and azimuth compression. Quasi-Newton method (QNM) would be utilized to search the optimal rotation angle for azimuth compression. The cost function has been defined as the entropy of focused image. At every range bin, targets with high signal-clutter-ratio (SCR) have been utilized because signal's entropy is sensitive to noise, leading it is not proper to apply full length samples. The exact range cell migration correction (RCMC) and motion compensation operations are necessary and prior to apply FRFT. Real data experiment has proved the validity of this algorithm.