Bistatic SAR Imaging Method Based On LEO Illuminator

Synthetic Aperture Radar（SAR）based on LEO illuminator refers to the bistatic Radar system consisting of the Low-earth-orbit platform as the transmitting station or airborne platform as the receiving station.The system has the advantages of wide beam coverage,high resolution and flexible configuration,ect,and has broad application prospects in terrain mapping,military reconnaissance,disaster monitoring and other fields.The high-precision range model,echo characteristics and imaging algorithms are the basic and key issues for the realization of LEO bistatic SAR imaging.In this thesis,theoretical analysis,method research,and simulation experiments are carried out for the above problems,and the theoretical method is verified by the LEO bistatic SAR test data.The main contents include the following aspects:1.The high-precision range model of LEO bistatic SAR is established,the echo model is derived,and the range migration and Doppler characteristics of the echo are analyzed,which provides a theoretical basis for the subsequent design of frequency domain imaging algorithms.2.The causes of Doppler aliasing in echoes of LEO bistatic SAR in sliding beamforming mode are studied,the characteristics of echo spectral ambiguity are analyzed,and a deblurring method based on pre-filtering is proposed.The SAR timedomain convolution function solves the problem of echo spectrum aliasing at low pulse repetition frequency,and realizes the reconstruction of the echo spectrum without Doppler aliasing.3.A two-dimensional frequency domain high-precision imaging algorithm based on the equivalent distance model of the circular orbit is proposed.The azimuth resampling is performed on the unambiguous echo signal to remove the azimuth space variation of the platform motion parameters.The two-dimensional stolt transform of the LEO Bi SAR is derived,and the consistent focusing of the scene target under the condition of twodimensional space variation of the echo spectrum is achieved,realizing high-efficiency and high-precision imaging.The above models and methods are verified by theoretical analysis and data simulation.The results show that the above method can effectively solve the Doppler aliasing problem of LEO bistatic SAR,and achieve high-efficiency and high-precision imaging.