Improved Azimuth Large-aperture Approach for Squint Airborne SAR

Airborne synthetic aperture radar (SAR) raw data are affected by variable aircraft parameters due to atmospheric turbulence and aircraft properties. In order to decrease the influence of variable aircraft information, the azimuth large-aperture approach is thus applied in airborne SAR real-data processing. However, it will cause the aliasing of azimuth-signal in squint SAR mode and degrade the image quality. In this paper, a novel model of airborne squint SAR instantaneous dopper frequency is constructed at first, then the study of azimuth sub-aperture spectrum extension and azimuth time-domain aliasing is presented. After that, a modified azimuth large-aperture approach is proposed to eliminate the aliasing in azimuth time-domain. Finally, simulations and experimental results of squint SAR mode are all provided to demonstrate the validity of the proposed approach.