New method for azimuth-dependent correction of highly squint missile-borne SAR subaperture imaging

Squinted imaging is one of the most important modes in the missile-borne synthetic aperture radar (SAR). Usually, from the view of practical applications, the missile-borne SAR adopts subaperture processing in order to implement quick look imaging. In the highly squint mode, the echo signal couples greatly between range and azimuth, so traditional algorithms perform the linear range walk correction in the azimuth time domain firstly to mitigate greatly the range-azimuth coupling, which causes the problem of position dependent azimuth phase, resulting in the azimuth uniform processing disabled and impacting the azimuth depth of focus (DOF). Based on the deep analysis of the instantaneous slant range model in the highly squint missile-borne SAR, this paper proposes high-order phase filtering to correct azimuth-dependence for implementing the identical azimuth-focusing processing. Simulation results validate the effectiveness of the proposed algorithm.