Focusing Highly Squinted Data Using the Extended Nonlinear Chirp Scaling Algorithm

The most serious problem in processing highly squinted data is the strong range-Doppler coupling, which can be reduced by the linear range cell migration correction (LRCMC). After the LRCMC, however, targets with different azimuth frequency modulation (FM) rates are moved into the same range cell, blocking the efficient azimuth compression. In this letter, a new algorithm to equalize the FM rates is presented, which is referred to as azimuth extended nonlinear chirp scaling. The key is to derive a new perturbation function to handle the problem while introducing a negligible residual phase. The proposed method outperforms the existing algorithms, particularly in large bandwidth cases. Numerical simulations illustrate the performance of the proposed algorithm.