Research On The Imaging Theory And Algorithms Of Geosynchronous Spaceborne-Airborne Bistatic SAR

With GEO-SAR satellite as the transmitter and airborne platform as the receiver,geosynchronous spaceborne-airborne bistatic SAR(GEO-BiSAR)is a new kind of bistatic SAR system.It has the advantages of wide beam coverage,short revisit cycle,long accessible period,high spatial resolution,flexible bistatic configuration and high survivability,etc,which make GEO-BiSAR highly valuable in many application areas,such as covert reconnaissance and hotspot surveillance.The basic and essential problems concerning GEO-BiSAR include system composition,imaging property,resolution performance,bistatic configuration,echo character and imaging algorithm.This thesis presents in-depth research on the theory analysis,method study and simulation experiments of the above problems.The main contents are as follows1.The quantitative model of the relation between spatial resolution,radiometric resolution and bistatic observation geometry is proposed.The non-orthogonality of the 2-D spatial resolution and the dependence of imaging performance on imaging geometry are revealed,which provide theoretical foundation for evaluating the imaging performance under certain observation geometry.2.The genetic GEO-BiSAR mission design method is proposed.By solving imaging nonlinear equation system using multiobjective genetic algorithm,the GEO-BiSAR geometry with desired imaging performance can be automatically generated under the constraints of system parameters and imaging performance.3.The differential evolution path planning method for GEO-UAV bistatic SAR is proposed.The method can automatically generate a set of UAV path in complex 3-D terrain,which simultaneously optimize the navigation and imaging performance for UAV receiver.4.The channel transfer function of multichannel GEO-BiSAR is derived.A channel configuration design method based on feasibility rule and a Doppler spectrum reconstruction method are proposed,which can generate the channel configuration with optimized azimuth ambiguity to signal ratio under the constraints of antenna size and SNR scaling.5.An Omega-K imaging algorithm for GEO-BiSAR is proposed.The 2-D spatial variance of range migration and Doppler parameters are solved by bistatic range history equivalence and 2-D Stolt transform.This method can achieve unified focusing for targets in different locations with high efficiency and accuracy and is suitable for different GEO-SAR orbit positions and receiver imaging modes,such as side-looking and squint mode.The above models and methods are verified by numerical simulation.The experimental results demonstrate that the proposed methods can effectively solve the problems in GEO-BiSAR application,such as mission design,path planning and Doppler spectrum aliasing,and achieve efficient and accurate imaging.