An improved frequency domain focusing method in GEO SAR

Geosynchronous orbit (GEO) synthetic aperture radar (SAR) has a lot of advantages due to its fine temporal resolution, but its imaging is much more difficult than low Earth orbit (LEO) SAR imaging. Via the analysis of GEO SAR's characteristics, the long synthetic aperture time (SAT) will cause large range migration and even more result in the failure of the line trajectory model; meanwhile the large propagation range will result in the failure of "Stop-and-Go" assumption, therefore the imaging algorithm in LEO SAR will lose effect in GEO SAR. Based on the above situation, the paper deduces the accurate range model using Norm method. The new range model can overcome the collapse of the line trajectory model, and considers the impact of the "Stop-and-Go" assumption. In sequence, an accurate imaging algorithm is deduced and proposed. The accurate imaging algorithm can overcome the impact of the "Stop-and-GO" assumption and obtain the space-variant two-dimensional reference function analytically, which can implement the large scene focusing under long SAT. The simulation results validate the correctness of range model and imaging algorithm.