Study Of SAR Imaging Algorithm Based On Complex Motion Platform

Synthetic Aperture Rader(SAR) is a high resolution imaging radar which can work in any weather and any time, therefore it is widely used in military and civilian fields. Affected by airstream, aircraft control systems, gravity and other factors, radar platform do the complex motion, the research of SAR based on complex motion platform high-resolution imaging technology is going deeper and further. The present thesis is focus on the imaging algorithm research of SAR based on complex motion platform, and have analyzed the trajectory modeling, the Doppler characteristic and azimuth resolution characteristic of the echo signal, the imaging properties and the imaging algorithms. The main contents of this thesis include the following three aspects:First of all, based on the airship kinetic equation, the range history model of spiral forward motion and uniformly accelerated curve motion is established. The Doppler bandwidth and azimuth resolution characteristics of SAR echo signal of complex motion platform are analyzed in detail. What’s more, this thesis has obtained a sufficient condition of that SAR of the complex motion platform has a higher Doppler bandwidth than SAR of the ideal motion platform. Therefore, for SAR based on complex motion platform, the-3d B width of the azimuth impulse response signal’s main lobe is used as the theoretical best azimuth resolution.Secondly, for SAR based on complex motion platform, the relationship between the Taylor series approximation order and effective synthetic aperture time is analyzed, it is concluded that the phase error will inevitably lead to the decrease of effective synthetic aperture and azimuth resolution, and the effect of motion measurement error on azimuth resolution is verified by simulation experiment. In addition, the acceleration tolerance when the Taylor series approximation of the point target range history can satisfy the imaging requirement is given. Because of the Spatial-Variant property of the Doppler history, BP algorithm is used in the scene imaging point by point.Last but not the least, the SAR imaging algorithm of complex motion platform is studied. BP imaging algorithm is used when the platform space position is exactly known, and when the motion sensor error is too large to image correctly, a BP algorithm based on phase tracking is proposed. The main procedures of the algorithm is: The first, the phase information and the slant range history of three strong scattering points are estimated by using phase tracking algorithm. Then according to the slant range history, solving the spatial position of the aircraft. Finally, using BP algorithm to achieve the scene imaging, and the effectiveness of the algorithm is verified by simulation.