An azimuth-variant autofocus scheme of bistatic forward-looking synthetic aperture radar

In bistatic forward-looking synthetic aperture radar (BFSAR), conventional autofocus algorithms cannot estimate the phase errors accurately when the range walk is compensated in the azimuthal time domain. This problem stems form the influence of the azimuth-variant Doppler coefficients after linear range cell migration correction (LRCMC) in azimuthal time domain. To cope with such a problem, an estimation equalization-estimation (EEE) autofocus scheme for BFSAR is proposed. Different from the conventional autofocus method, the azimuth-variant Doppler coefficients are additionally estimated and equalized. As the influence of azimuth-variant Doppler coefficients has been greatly reduced, conventional autofocus method is subsequently applied for accurate phase error retrieval. Simulation results demonstrate the validity of the proposed method on the improvement of autofocus in BFSAR.