Research Of An External Calibration Method Of Spaceborne Aperture Synthesis Radiometer

Microwave radiometer is a kind of high sensitivity receiver for measuring microwave radiation energy,and it has a broad application prospect in military,transportation,security and Earth Science fields.The aperture synthetic radiometer(ASR)utilizes small aperture antenna arrays to synthesize a large one to solve the problem that the traditional microwave radiometer requires a large physical aperture to obtain the desired spatial resolution at low frequency,so it has a high research value.In the ASR system,good correction of system error is the precondition of obtaining high quality image.As an important part of the system,the antenna array is the major object of the research.In this thesis,an external calibration method for spaceborne ASR is proposed,and researches are carried out,including simulation analysis towards the proposed external calibration method,preform outfield verification experiment,analyze the layout details and ultimately determine the implementation scheme.Firstly,based on the thorough study of the ASR working principle and summarizing the system error and calibration methods,the external calibration method of spaceborne ASR was designed which is used for calibrating the antenna phase error and antenna position error.Then,establish the extended source imaging system of cross-shaped antenna array ASR and prove the effectiveness of the proposed method by simulation.In the next,the outfield experiment was carried out by using the X band two-dimensional aperture synthetic experimental system.In the experiment,noise point sources,buildings and characters were observed and calibrated respectively,and the good calibration results verify the feasibility of the method.Afterwards,discuss the layout details of point sources,refer to the optimal location and quantity of the calibration points and the like.Finally,summarize and derive two concrete implementation schemes of the external calibration method according to different requirements.The external calibration method proposed in this thesis breaks down the limitation that the traditional aperture synthetic system calibrates the antenna error only on the ground,meanwhile,it avoids the weakness of the available spaceborne calibration method that the aircraft needs to be turned,which is also the innovation of this thesis.To sum up,the method is of certain referential value to the image quality improvement and the practical engineering realization of ASR.