Focusing translational variant bistatic forward-looking SAR using extended nonlinear Chirp Scaling algorithm

With appropriate geometry configurations, bistatic Synthetic Aperture Radar (SAR) can break through the limitations of monostatic SAR for forward-looking imaging. This paper develops an extended nonlinear Chirp Scaling imaging algorithm for translational variant BFSAR. The method utilizes a point target reference spectrum of generalized Loffeld's bistatic formula (GLBF). Without bistatic deformation term, GLBF is the latest development of Loffeld's bistatic formula. After an azimuth frequency transformation in 2-D frequency domain, the azimuth spatial variation is removed. Then through a fourth-order frequency domain filtering, the algorithm can consider the quadratic variance term of the range frequency modulated rate and the linear term of the tertiary coupling phase term along cross-track direction. In addition, by a fourth-order nonlinear Chirp Scaling equalization operation, the algorithm can finish the correction of quadratic range cell migration in terms of range. The result of this paper can be used for forward-looking reconnaissance, guidance and so on.