Study On Systems Of Airborne Squint Mode And Forward Looking Mode Synthetic Aperture Radar

Airborne squint mode SAR and forward looking mode SAR are hot research fieldsin SAR. Airborne squint mode SAR and forward looking mode SAR have moreadvantages compared with side looking mode SAR: Airborne squint mode SAR hasmore flexibility in beam direction, which enhancing safety and concealment ofplatform; Airborne squint mode SAR has the capability of flexibly choicing imagingfield including front and back of platform; Airborne forward looking mode SAR canobtain high resolution images in front of the flying track etc.In this dissertation, system property, imaging process and high resolution imagingalgorithms of airborne squint mode SAR and forward looking mode SAP, are studiedin detail. This dissertation is devoted to:(1) The property of squint mode SAR is researched deeply. The range azimuth coupleof airborne squint mode SAP, in time domain and frequency domain is analyzed,the character of range cell migration of airborne squint mode SAR is studied andimaging algorithms selection for different range migration situations are analyzed.Azimuth spectrum expansion of squint mode SAR is studied, effective azimuthbandwidth expression is deduced and PRF selection scope of squint mode SAR isobtained according to the effective azimuth bandwidth.(2) The squint mode SAR echo signal simulation is studied and squint mode SARecho signal simulation method is proposed. Geometry model of squint mode SARecho signal simulation is established and calculation expressions of several keyparameters for simulation are obtained according to detailedly mathematicalanalysis and deduction. (3) SAR imaging algorithms are studied in retail and improved RD algorithm, CSalgorithm, NCS algorithm for large squint mode SAR are proposed. Flow andprocessing steps for three improved algorithms are provided and all phasecompensating factors in algorithms are deduced. Validities of three improvedalgorithms are validated by squint mode SAR imaging.(4) The property of forward looking mode SAR is researched. Operating principle offorward looking mode SAR is analyzed and imaging geometry model and echosignal model are established. Azimuth property of forward looking mode SAR isanalyzed, doppler frequency, effective synthetic aperture length and azimuthresolution expression are achieved. Several factors affecting azimuth resolutionare analyzed in detail.(5) Imaging algorithm for forward looking mode SAR is studied. CS algorithm forforward looking SAR imaging is proposed, flow and processing steps are givenand points imaging is achieved. Point response quality is analyzed and comparedwith theory value, Validity of proposed CS algorithm is validated by pointsimaging and quality analysis.