Two‐dimensional frequency decoupling method for curved trajectory synthetic aperture radar imaging

Abstract

Synthetic aperture radar (SAR) imaging with curved trajectory is difficult due to its severe two-dimensional (2D) space variance. When processing the echo with azimuth-variance, the range cell migration and Doppler modulation of the targets with different azimuth locations are different, which brings a big challenge to image formation. Here, a 2D frequency decoupling method for this case is proposed. Firstly, the range history of the curved trajectory is accurately modelled based on fourth-order Taylor series expansion. Then, the 2D point target reference spectrum of the echo signal is obtained by the method of series reversion. The 2D space variance characteristics of two typical cases with curved trajectory, i.e. geosynchronous SAR and missile-borne SAR, are analysed. Based on the space variance characteristics, a 2D frequency decoupling step is implemented to handle the space-variant phase. Simulations are presented to demonstrate the effectiveness of the proposed algorithm.