Imaging algorithm based on Least-Square NUFFT method for spaceborne/airborne squint mode bistatic SAR

In this paper, a frequency domain imaging algorithm is proposed for the spaceborne/airborne bistatic synthetic aperture radar (SA-BSAR) with highly squint angle. The imaging processing is carried out with the following two stages. In the first stage, the space-invariant part of the raw spectrum data is compensated by multiplying with the conjugate of the spectrum from the reference target. In the second stage, the two-dimensional space-variant component, which manifests obvious nonlinear coupling between the range frequency and the Doppler frequency in the high squint case, is effectively corrected by the two-dimensional non-uniform fast Fourier transform (NUFFT) operation. The computation burden of the proposed imaging reconstruction method is O(MN logMN), where MN is the number of the image pixels. Simulation experiments demonstrate the validity of the proposed method.