The space-variant defocus effect introduced by wavefront curvature in polar format algorithm (PFA) imagery limits its maximal focused scene size.Several compensation strategies have been developed in literature to solve this problem

e.g.

subaperture processing

space-variant post processing and widefield polar format algorithm.However

all these approaches are based on the assumption that radar platform is following an expected linear trajectory.They still can’t meet the required precision when imaging from arbitrary radar flight path.In this paper

an improved space-variant post processing method for wavefront curvature compensation is proposed.The method computes wavefront curvature error in original phase history domain

and then transforms it into spatial frequency domain by polar format transformation used in image formation.Using the transformed error

we can accurately compensate wavefront curvature effect by space-variant post filtering.Simulation experiments show that the new algorithm has improved focused scene size when applied to phase history generated by non-ideal radar flight path.