Research On Distributed Spaceborne Multichannel SAR Echo Simulation And Software Implementation

Spaceborne synthetic aperture radar(SAR)is a ground observation system based on microwave remote sensing technology.With the development of SAR technology,SAR applications are no longer limited to two-dimensional imaging,but have developed to a couple of advanced technologies,including interferometric synthetic aperture radar(In SAR),which is used to obtain global Digital Elevation Model(DEM)and differential interferometric synthetic aperture radar(DIn SAR)technology,using for acquiring the surface deformation.Compared with traditional SAR systems,the distributed spaceborne multichannel SAR has several advantages,such as high resolution,wide swath,and low temporal decorrelation.Compared with airborne SAR,however,the real measured data of spaceborne SAR is relatively scarce due to the high cost,high risk and long period factors,which limits the development of spaceborne SAR.At present,there is no on-orbit distributed spaceborne multichannel SAR system in China.In order to help the researchers to better perform distributed spaceborne multichannel SAR,for example,parameter optimization,system performance analysis and processing algorithm research,this article focuses on the research of high-precision and high-efficiency distributed spaceborne multichannel SAR echo simulation technology.According to the theory of distributed spaceborne multichannel SAR system,this article implements the research contents in the form of software.The main research contents are as follows: 1.Introduction of distributed spaceborne multichannel SAR system theories.Firstly,the geometry of distributed SAR satellites is introduced in details,including satellite formations,orbit model and attitude model.Secondly,the echo link of the distributed spaceborne multichannel SAR is analyzed.Finally,the non-ideal factors of spaceborne SAR system are summarized,including the USO(ultra stable oscillator)error and channel mismatch error of distributed spaceborne multichannel SAR.2.Key technologies of distributed spaceborne multichannel SAR echo simulation.The key technologies of SAR echo simulation includes non-ideal factors modeling,electromagnetic modeling and bistatic SAR echo calculation.The calculation of bistatic SAR echo time delay is emphasized in this article.Based on the influence of non-ideal factors,the models of non-ideal factors for distributed spaceborne multichannel SAR are given;the measured DEM is used as the scene terrain,and the bistatic scattering coefficient is calculated using the Kirchhoff approximation.The mathematical model of SAR echo is derived and analyzed.Meanwhile,the error and influence of the echo time delay calculation of the spaceborne SAR is analyzed caused by the "stop-go" hypothesis.The none "stop-go" echo acquisition geometry of spaceborne SAR is analysized.By analyzing the echo acquisition geometry of the spaceborne SAR in none "stop-go" mode,this paper proposes a fast bistatic SAR echo time delay algorithm,called fast algorithm.Simulation experiments demonstrate that the proposed fast algorithm can obtain the same accuracy as the traditional iterative method,while the time cost is similar to the "stop-go" hypothesis simulation.Therefore,it is proved that the fast algorithm has the advantages of high precision and high efficiency.3.Software implementation of distributed spaceborne multichannel SAR echo simulation.The design framework and pattern of the software are given,and functions of each module are realized based on the C ++ language.In order to evaluate the performance of the software,the distributed spaceborne multichannel SAR / In SAR echo and the DIn SAR echo are simulated using this software.Then,the echos are processed and performance evaluated.The performance evaluation results prove the effectiveness of the simulation software designed in this paper.