ISAR Imaging Algorithm of Maneuvering Targets Using the Second-Order Keystone Transform

In response to the problem that a maneuvering target with complex motions could cause the first order range migration and the second range migration within a coherent processing interval, a 2D ISAR imaging algorithm using the second-order keystone transform in this paper. First, the echo signal model of a maneuvering target is build up and analyzed according to the dechirp-on-receive technique, and the second order keystone transform is used to remove the second-order range migration. Then, the FrFT is used to estimate the chirp rate of the newly resulting quadratic phase term, and the estimated chirp rate is utilized to compensate for the quadratic phase term. The second-order keystone transform is again applied to the compensated echo signal to remove the first-order range migration. Finally, applying 2D FFT to the compensated echo signal to obtain a high-resolution 2D ISAR image. The numerical simulation and real data are conducted to verify the validity of the proposed imaging algorithm.