Abstract: Spaceborne bistatic synthetic aperture radar (SAR) systems transcend the geometric limitations of traditional monostatic SAR imposed by co-located transceiver configurations. By leveraging flexible spatially separated configurations, these systems enable a variety of advanced operating modes. However, bistatic SAR imaging under squint geometries suffers from severe spectrum distortion and exacerbated spatial-variant errors, resulting in degraded image quality. To address these challenges, this paper extends the numerical calculation-based Equivalent Monostatic Algorithm (EMA)—originally derived for broadside geometry—to the squint configuration of spaceborne bistatic SAR. Specifically, the proposed method transforms the squint data into an equivalent broadside geometry by utilizing linear Range Cell Migration Correction (RCMC) and two-dimensional frequency-domain azimuth resampling. Subsequently, based on the bistatic slant range history, a least squares fitting method is employed to estimate key parameters, including the equivalent squint angle and equivalent velocity, thereby completing the residual RCMC and realizing precise focusing. This approach effectively resolves the squint imaging limitations associated with the numerical calculation-based EMA. Finally, simulation experiments are conducted to validate the effectiveness of the proposed method.

Key words: spaceborne BiSAR, squinted imaging, azimuth resampling, linear range cell migration correction (LRCMC), monostatic equivalent