Motion Compensation In Airborne Ultra-Wideband Synthetic Aperture Radar

Trajectory deviation of the aircraft is the main cause of phase errors in airborne Ultra-wideband Synthetic Aperture Radar (UWB SAR). So, motion compensation is the premise to realize high-resolution image. It is one of the key technologies in UWB SAR.It is considered in this dissertation that motion compensation in airborne UWB SAR is used to eliminate the phase errors caused by the aircraft, and thus to improve the image quality. Firstly, we study the application of Global Positioning System (GPS), Inertia! Navigation System (INS) and integrated navigation system in airborne UWB SAR system. A simplified integration system is proposed in the dissertation. We also analyze principle of Reflective Displacement Method (RDM) to estimate velocity of the aircraft. Then the Improved RDM (IRDM) which can be applied in UWB SAR is proposed.Considering the information redundancy and complementary in the two compensation methods, we use data fusion method in airborne UWB SAR motion compensation. We express the true trajectory of the aircraft by means of spline function, and then use measuring data from multichannel to estimate the spline coefficient. It takes accounts of the characteristic of the airborne motions and UWB SAR, and thus improves the performance of motion compensation.Finally we separate the aberration into space invariant and variant component, which are eliminated by first and second-order compensation procedure respectively. Then a method to integrate motion compensation in Range-Doppler (RD) imaging algorithm is presented. We also design the approach to evaluate the errors from the imaging result and thus eliminate them.