Spaceborne Sar Channel Modeling And Echo Detection Performance

Comparing with space-borne optical system, the space-borne SAR (Synthetic Aperture Radar) system has obvious advantages, provide rich information about the surface scattering and it can work in all weather during day and night, and it also have the ability to detect hidden targets. In recent years, the space-borne SAR detection and surveillance techniques for sea target have been widely applied in military reconnaissance, ship detection and fish resource protection and so on.The accurate simulation of Space-borne (SAR) echo raw data affects the high resolution imaging algorithm validation and SAR system performance evaluation directly. It has great significance for the development of space-borne SAR system.The present research on satellite mobile communication channel focuses on the effects of satellite-ground one-way link on the radio propagation, but in the environment of space-borne SAR, the signal needs to travel in the satellite-ground and ground-satellite round-trip link, pass through the atmosphere twice and be reflected by ground targets, so the propagation environment is much more complicated. For the accurate simulation of Space-borne Synthetic Aperture Radar (SAR) echo raw data, we establish a round-trip channel model and give the theoretical expression for space-borne SAR on the basis of the classic model of C.Loo, and design a corresponding simulation model based on sum of sinusoids. Simulation results indicate that the probability density function (PDF) of the simulation model is close to that of the theoretical model. And then considering the decline of signal amplitude caused by atmospheric propagation and the phase change caused by the ionosphere, we discuss the approach of establishing the space-borne SAR echo signal model which is affected by the round-trip channel, and analyze deeply the radiation resolution and the spatial resolution of SAR images.It is necessary to find an effective approach to improve the space-borne SAR detection performance with sea clutter. In this dissertation, considering the space-borne SAR detection performance with sea clutter, we propose a Doppler-CFAR detection algorithm based on the traditional CFAR detection algorithm. The new algorithm have a different detection threshold for each Doppler bins with the same false probabilities. At last, theoretical analysis and simulation experiments show that the new algorithm not only can reduce the amount of computation, but also can improve the detection performance.