Airborne Multi-channel SAR Imaging And Error Compensation

There is no doubt that the Synthetic Aperture Radar(SAR)is a well-proven imaging technique for remote sensing of the Earth,and it is highly valuable for both military and civil application in recent years.However,conventional space-borne SAR systems are not capable of fulfilling the increasing demands for high resolution and wide swath(HRWS).To overcome these inherent limitations,one innovative technique has been proposed which employs multiple receiving channels to gather additional information along the synthetic aperture direction,that is,“multi-channel technique”.Because the space-borne system possesses some drawbacks,such as high design cost,not easy to maintain,upgrade and operate,and long development period,it is very limited in system design and algorithm verification.In order to quickly realize the load performance optimization prediction of the multi-channel space-borne SAR imaging system,this dissertation has studied the equivalent data obtained by the airborne equivalent verification system to verify the space-borne multi-channel SAR imaging technology.In the course of the research,we focus on the multi-channel azimuth ambiguities suppress technique,the channel errors compensation technique and the motion errors compensation technique.The main work of this dissertation is as follows:1.An azimuth multi-channel SAR echo signal model is established for airborne multi-channel SAR system,and the equivalent phase compensation formula is derived.On the basis above,two typical algorithms for suppressing Doppler ambiguities(the multi-channel transfer function method and the STAP-based approaches)are studied.Based on the airborne simulation data,the azimuthal multi-channel SAR ambiguities suppress performance is verified.The results show that the performance of azimuth multi-channel ambiguities suppress processing is robust and effective in multi-channel SAR imaging.2.The factors influencing of channel errors of airborne multi-channel SAR system are analyzed,which mainly include the channel gain,phase and position errors between channels.Then the influence of channel error factors on airborne multi-channel imaging is analyzed.A channel errors estimation method is introduced,and the effectiveness of the method is verified based on the airborne simulation scene data.3.A motion compensation method for airborne multi-channel SAR imaging system based on POS(Position and Orientation System)measurement data is studied.This method uses the POS measurement data to obtain the position offset and attitude change of the radar antenna phase center(APC),and motion compensation with reference to the ideal imaging geometry.To minimize the influence of the errors on the estimation of the phase error between the channels and the suppression of the Doppler ambiguity,it is necessary to consider how to compensate all kinds of errors as much as possible.4.Using the method proposed in this dissertation of airborne multi-channel SAR imaging,the two sets of airborne multi-channel measured data is processed.In the analysis,not only the final results were evaluated,but also a detailed description of the middle process steps is given.The validity of the proposed method is verified by two sets of airborne multi-channel measured data.