GEO-LEO Bi-SAR Imaging Technology

In this thesis, the technologies of imaging by Geosynchronous Satellite systemare researched. Firstly, the system features and parameters of GEO Mono-SAR andGEO-LEO Bi-SAR are analyzed in detail, and the feasibilities are preliminarydemonstrated. Then a Reversion of the Series based GEOSAR imaging algorithm isproposed to solve the ground targets imaging problems cause by the curvilinearmotion of GEO satellite. Further the GEO-LEO Bi-SAR imaging model isconstructed, on that basis, a Doppler Distribution Weighted method is proposed toestimate the two dimensional spectrum, then the Inverse Scaled Fast FourierTransformation is introduced to achieve the ground target imaging by GEO-LEOBi-SAR system. The main contents are as follows:1) To overcome the features and prameters analyzing problem, the indexes ofimaging resolution, space variale feature, fuzzy performance, doppler feature,synthetic aperture time, imaging bandwidth are proposed. The formulas arederivated in GEO Mono-SAR and GEO-LEO Bi-SAR system. Difference of thesystem features are analyzed. On this basis, a Normalization Back ScalingCoefficient is proposed to measure the system dependence on system parameters,and the feasibilities of the two systems are primary demonstrated.2) To overcome problem that the traditional frequency domain imaging isn’tsuitable in the curvilinear motion between the long synthetic aperture time ofGEOSAR, a Reversion of the Series improved Chirp Scaling algorithm is proposedto achieve high resolution imaging by GEOSAR. The method is compared to classictime domain imaging method-Back Projection algorithm, performance comparedresults indicate the advantage of the algorithm.3) To overcome the imaging problem cause by different orbits of GEO and LEO,a motion variable Bi-SAR model of different height, location and velocity, then thetwo-dimensional spectrum estimation is concluded to be the key of imaging byGEO-LEO Bi-SAR system. Further a DDW method is proposed, which solves theproblem that Stationary Phase Principle can’t be used directly. The method iscompared to classic Loffied’s Bistatic Formula and Extended Loffied’s BistaticFormula methods, the theoretical analysis and simulation results shows theadvantages of the method.