Approach for airborne radar ISAR imaging of ship target based on generalized keystone transform

High resolution image of ship target under low SCNR condition is unable to be obtained by conventional ISAR imaging methods when long coherent integration time needed. To overcome this problem, a novel approach for imaging the ship target by airborne radar is proposed in this paper. Firstly, the generalized keystone formatting is applied to compensate the range curvature induced by long integration time. Secondly, the quadratic term of slow time in phase is eliminated by estimating the target motion parameter using Radon-Ambiguity Transform (RAT) scheme. Next, generalized keystone formatting method is used again to eliminate the residual linear range walk. Finally, the high resolution image of ship is obtained by employing the Relax algorithm. Results of both simulation and real data are presented to confirm the validity of the proposed algorithm.