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A Modified Nonlinear Chirp Scaling Algorithm Based on the Numerical Estimation

The nonlinear azimuth chirp scaling (NLCS) algorithm was often used to perform the azimuth equalization in bistatic high-squint or forward-looking synthetic aperture radar (SAR) recently. However, the original NLCS algorithms cannot focus the data well in azimuth variant bistatic forward-looking SAR (BFSAR) due to its two-dimensional spatial variation. In this paper, we modify the NLCS algorithm based on the numerical estimation to generate an estimated perturbation function to equalize azimuth Frequency Modulation (FM) rates of different targets. Assuming that the linear range walk has been corrected, and then a modified NLCS algorithm is utilized to preprocess the data for azimuth compression. Simulation results verify the proposed NLCS algorithm well.