Research On UVA Sar Imaging Algorithm

Compared with the conventional radar, synthetic aperture radar (SAR) has many advantages, which uses pulse compression technology and synthetic aperture techniques to obtain high-resolution two-dimensional target not only can detect the existence, distance of a target, but also is able to imaging a target all-weather, all-time. Because of so many advantages, SAR has been used in military and civilian fields more and more widely. With the technology developing, satellites and unmanned aerial vehicles (UVA) has become the new carrier for SAR. UAV is small and flexible, difficult to be found, so it can close to enemy areas to reconnoiter, avoid the risk of casualties. But because of the large air disturbance, UVA can not make a smooth flight, so the motion compensation for UVA SAR is extremely important.SAR imaging is based on two-dimensional high-resolution, this paper discussed the mechanism of SAR imaging, established airborne SAR model, then introduced several imaging algorithms, the basic R-D algorithm for range migration can be ignored in the case; CS algorithm can do range migration correction in all range unit; RMA algorithm theory can completely correct range migration, but the computation is huge.Motion compensation is a critical issue for UAV SAR, this paper researched motion compensation based on echo data. The motion error of carrier aircraft caused echo phase error, so the image can not be properly focused, even can not imaging at all. So this paper analyzed the phase error first, then classified phase error by a variety of standards, discusses the motion compensation method. Motion compensation based on Doppler parameter estimation including Doppler center frequency estimation and Doppler frequency rate estimation, MD method can compensate quadratic phase error accurately; PGA compensation is based on complex image, it is not based on model, so in theory can compensate for any order of the phase error through multiple iterations to achieve accuracy. For UAV SAR, a motion compensation method based on wave path difference of significant point were proposed, this method starting from the principle of azimuth compression, can compensate echo phase error accurately by Interpolation.