An Accurate Range Model Based on the Fourth-Order Doppler Parameters for Geosynchronous SAR

This letter presents an accurate range model, named as Doppler parameter range model (DRM), to perform signal processing for geosynchronous synthetic aperture radar (Geo-SAR). Besides that a credible approach, defined as accurate coordinate numeric model (ACNM), is proposed to simulate the raw echo signals. To improve the accuracy of DRM and ACNM, the rotating Earth is modeled as an ellipsoid and the eccentricity of the satellite´s orbit is analyzed. The superiority of DRM that it is more precise than hyperbolic range equation (HRE) and advanced hyperbolic range equation (AHRE), presented before, is illuminated. The point target 2-D frequency spectrum of DRM is derived. Finally, the simulation results validate that DRM and ACNM has a good effect on an L-Band Geo-SAR system with an azimuth resolution around 5 m.