Bistatic synthetic aperture radar (BiSAR) imaging is faced with two major challenges: large scene imaging and adaptability to unideal platform motion in practice. In order to deal with these two problems, a generalized wavefront-curvature-corrected polar format algorithm (PFA) is proposed in this article. The traditional PFA is little restricted on geometry configuration and platform motion, but its application to large scene imaging is limited by the far-field planar wavefront assumption. To solve this limitation, this article derives the phase error caused by wavefront curvature and analyzes its influence on both geometric distortion and defocusing effect in detail. Based on the analysis, we present a wavefront curvature completely correcting method through space-variant phase compensation using the analytical wavefront curvature phase in wavenumber-domain, which is derived through method of series reversion. What's more, an efficient realization of the space-variant phase compensation based on two-stage image division is given to avoid high overlap rate in the traditional image division method. The proposed method can obtain well focused and geometric undistorted image for BiSAR under complicated flight paths, and it also keeps the logarithmic complexity of traditional PFA. The effectiveness of the proposed method is verified by numerical simulations.

中文翻译：

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复杂飞行路径下双基地SAR聚焦的广义波前曲率校正极坐标格式算法


双基地合成孔径雷达（BiSAR）成像面临两大挑战：大场景成像和实际中对不理想平台运动的适应性。为了解决这两个问题，本文提出了一种广义波前曲率校正极坐标格式算法（PFA）。传统的PFA对几何结构和平台运动的限制很少，但其在大场景成像中的应用受到远场平面波前假设的限制。为了解决这一局限性，本文推导了波前曲率引起的相位误差，并详细分析了其对几何畸变和散焦效果的影响。在此基础上，利用级数反演法导出的波数域解析波前曲率相位，提出了一种通过空变相位补偿来完全校正波前曲率的方法。此外，还给出了基于两级图像分割的空变相位补偿的有效实现，以避免传统图像分割方法中的高重叠率。该方法能够在复杂飞行路径下获得聚焦良好、几何不失真的BiSAR图像，同时保持了传统PFA的对数复杂度。通过数值模拟验证了该方法的有效性。