An improved omega-K algorithm-based method for electromagnetic vortex imaging in squint

Abstract In high-squint airborne synthetic aperture radar (SAR) imaging, severely constrained Doppler bandwidth and intensified range-azimuth coupling lead to significant degradation in azimuth resolution, imaging geometric distortion, and worsened sidelobe performance. This paper proposes a time-varying vortex electromagnetic wave squint (VEMS) SAR imaging algorithm based on an enhanced VEMS Omega-K algorithm. To address resolution degradation and sidelobe performance deterioration, this algorithm introduces OAM mode numbers that linearly vary with slow time to broaden the range-Doppler bandwidth and enhance imaging clarity. To address geometric distortion, it combines the FORM4 fourth-order slant range model with wave-number domain coordinate rotation and high-order phase compensation, enabling precise range migration correction and signal focusing under large squint angles and conditions of platform acceleration. Experimental results demonstrate that the proposed algorithm maintains robust focusing performance at high squint angles. It significantly outperforms conventional Omega-K algorithms in azimuth resolution, mainlobe energy concentration, and sidelobe suppression, offering an effective solution for high-squint SAR imaging.