High Squint SAR Imaging Using the Modified Range-Doppler Algorithm

Based on the imaging geometry of squint mode, the characteristics of echoes based on four order approximate expressions in slow time domain in squint mode are analyzed in this paper. The conclusion that the influence of range walk is much larger than range bending in high squint mode is drawn. The traditional Range-Doppler algorithm is no longer suitable for high squint SAR imaging. Based on the conclusion a modified Range-Doppler algorithm suitable for high squint SAR imaging is derived in this paper. At first range walk is corrected in range frequency domain to make the coupling between range and azimuth small. After that, range compression, secondary range compression, azimuth compression and higher order phase correction are presented in the modified algorithm. Compared with the traditional Range-Doppler algorithm, the imaging results of simulation are presented to demonstrate the accuracy and validity of the proposed algorithms in high squint SAR imaging.