Research On GEO SAR Long Synthetic Aperture Time Echo Simulation And Software Design

The advantages of GEO SAR,such as high resolution and wide mapping,make it a hot spot for the research at home and abroad.Compared with traditional medium-low-orbit satellites,GEO SAR has many new features in terms of imaging processing,echo simulation,and error analysis.In recent years,researchers have made numerous achievements in system analysis and imaging algorithm of GEO SAR,but there is still a lack of research about the effects of non-ideal factors on GEO SAR imaging.In order to simulate and analyze the performance of GEO SAR and provide theoretical support for system design,this thesis first classifies the various non-ideal factors of GEO SAR,and makes a brief analysis,then it gives simulation analysis about impact on the ionosphere,weak ground coherence and earth tide.At the same time,echo has a serious decoherence effect,because of the long synthetic aperture time characteristics of the GEO SAR and the time-varying feature of the sea surface,which causes GEO SAR cannot form the image of the sea surface.In contrast,the synthetic aperture time of LEO SAR is very short,which doesn't cause serious decoherence of SAR echo.Therefore the deep research of ocean simulation in this paper is based on LEO SAR model.Aiming at satisfying above simulation requirements,this thesis developes a set of GEO SAR long synthetic aperture time echo simulation software that integrates sea-land scene echo simulation,imaging processing,performance analysis and non-ideal error factor simulation.The main work of the thesis is summarized as follows.1.Firstly,the various non-ideal error factors of GEO SAR are classified into four parts: satellite platform error,payload error,transmission link error and observation scene error,and the errors of each module are briefly analyzed.Then,according to the new characteristics of GEO SAR,detailed theoretical analysis and simulation verification of ionosphere impact,weak ground coherence,and earth tide are performed respectively.2.Starting from the wave spectrum,several familiar wave spectra are introduced in succession.Based on this,the classical modeling method is used to simulate the sea surface,achiving a accurate description of the sea surface,and then the small facet model is applied to simulate sea surface electromagnetic scattering.In order to improve the simulation efficiency,this paper proposes a fast time domain simulation method to complete the echo simulation of the dynamic sea surface scene.Finally,the BP algorithm is used for imaging processing,and then ATI method is utilized to complete the dynamic sea surface velocity measurement.3.In the first place,this section introduces the system architecture of GEO SAR long synthetic aperture time echo simulation software,and divides the software architecture into three layers: interface presentation layer,business processing layer,and database access layer.Then software design of the ionosphere,ground weak coherence,earth tide and echo simulation are introduced in detail.Finally,the design and implementation of software modules are briefly narrated,and the interface of error effects are exhibited.