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Focusing of Maneuvering High-Squint-Mode SAR Data Based on Equivalent Range Model and Wavenumber-Domain Imaging Algorithm

Due to the complexity of high-squint synthetic aperture radar (SAR) mounted on maneuvering platforms, the traditional geometric model and imaging algorithms cannot be directly applied in the diving or climbing stage for the existence of vertical velocity. Aiming at this issue, an equivalent geometric model of maneuvering high-squint-mode SAR is constructed, and a modified wavenumber-domain imaging algorithm combined with the proposed equivalent range model is proposed in this article. First, the disadvantages of the conventional range model are analyzed in detail and an equivalent range model is proposed to describe the motion characteristic of squint SAR in maneuvering mode, which maintains the azimuth-shift invariance along the flight direction in the new slant range plane. Then, to achieve the requirement of maneuvering SAR real-time processing, a modified wavenumber-domain imaging algorithm with a high usage of the spectrum by axis rotation for high-squint SAR data is proposed. Further, since the equivalent model may introduce the severe distortion in the imaging plane, a novel geometric correction method based on inverse projection is performed to obtain the ground imagery with a little distortion. Finally, simulation and real-data processing results validate the superiority of the proposed algorithm.