HotZ-雷达系统(第六章)合成孔径雷达

SAR（合成孔径雷达）雷达成像原理目标的尺寸和形状2cRB012kD距离分辨力：角分辨力：τ：脉冲宽度B：信号带宽β0：天线半功率宽度λ：信号波长D：天线孔径提高切向维分辨力的常用方法：当雷达和目标间有相对运动时出现fd，利用多普勒频域的分辨力来获得切向维的分辨力。2c常规脉冲雷达利用足够高的分辨力获得利用足够高的分辨力获得信号带宽越宽，距离分辨力越高波束越窄，角分辨力越高真实孔径雷达：侧视雷达向侧面发射一束脉冲，地物的反射回波，由天线收集，记录。合成孔径雷达：利用一个小天线作为单个辐射单元，沿一直线方向不断移动，在移动中选择若干位置发射信号，接收相应的发射位置的回波信号，存贮接收信号的振幅和相位。雷达成像方式雷达移动方向雷达移动方向合成孔径雷达：在不同位置接收同一地物的回波信号。真实孔径雷达：在同位置接收目标的回波信号。雷达成像结果RangeResolution（距离分辨率）DrRRSlantrange（斜距）pulseoflengthlightofvelocitywhere)sin2/(pprccRpulseoflengthlightofvelocitywhere2/pprccRRange（距离）RangeResolution（距离分辨率）Whenusingpulsecompressiontechnique脉冲压缩技术DrRRsin2RrBcRBR:ChirpbandwidthExample:Pulselength=0.1milli-seconds,lookangle=30oR’r=0.1x10-3x3x108/2=15kmRr=R’r/sin(30o)=30kmUsingrangecompressionmethod:m20)30sin(1055.152103sin268RrBcRAzimuthResolution（方位分辨率）Azimuthresolutionofrealapertureradar真实孔径雷达的方位向分辨率antennaphysicaloflengthwavelengthrangeSlantwhere/DRDRR!!km!5.4~R,10D0.056m,km,800R：ERS1/2ofExamplemDRRSAR（合成孔径雷达）Throughthemovingofantennaalongaline,imageasceneforanumberoftimes。通过沿着一条直线移动天线，对同一地物多次成像Synthesizethemultipleimagingdataofascenetooneimage。把同一地物的多次成像合成为一幅图像Equivalentto“enlarge”theantenna,formingaverylongantennaandthusimprovingtheazimuthresolution等效于增大天线，形成一根很长的天线，从而改善分辨率SketchMap（示意图）(FromGlobeSARprogram,CCRS)1234DecompositionofMultipleImaging（多次成像分解示意图）SynthesisofMultipleImaging（合成）ObjectsexperienceilluminationoveratimeintervalRecordandsavethecompletehistoryofreflections（记录和保存了完整回波信号）Permitsreconstructionofthereflectedsignals（反射信号重建）BasedontheprincipleofDopplerfrequencyshiftcausedbytherelativemovementbetweentheantennaandthetarget（依据多普勒频移原理）Bytracingthefrequencyshiftsandthussynthesisingthecorrespondingechoes,theazimuthresolutioncanbesharpened(SARfocusingtechnique)（根据多普勒频移，合成相应的回波，改善方位分辨率，称为SAR成像或聚焦过程）(Courtesy:CCRS)(Courtesy:CCRS)ForERS-1/2,a10mantennaisusedtosynthesizeanearly5kmantenna.About1000radarimagesareusedtogetoneSARimage.RenewedAzimuthResolution(更新的方位分辨率)DRRDDRDRRgenerally,antennadsynthesizeoflengthwavelengthrangeslantwhere/2/resolutionazimuthrenewedgetthewetrip,roundiontheconsiderattakingand,intoInsertingDRRDRDSyntheticapertureradar（合成孔径雷达）方位分辨能力与距离无关Example:ERS-1/-2SARResolutionAntennalength:L=10mTypicalrange:km85323cos/satHRm25)23sin(1055.152103sin268RrBcRGroundrangeresolution:km510/056.0853000DRRAzimuthresolution:m52/102DR(Crimea,Ukraine)RealApertureRadarSyntheticApertureRadar5x14kmpixels4x20mpixelsMassonnetandFeigl,1998~TheEnd~Thankyou!