合成孔径雷达概念.ppt

第二章.Concept of SAR（合成孔径雷达概念）Radar Resolution（分辨率）oRange resolution（距离向分辨率）-Range resolution is dependent on the length of the pulse(脉冲长度);脉冲越短，分辨率越高。oAzimuth resolution（方位向分辨率）-Azimuth resolution is determined by the beam width（波束宽度）；波束越短，分辨率越高.Range Resolution（距离分辨率）Antenna Flight directionAzimuth direction q D Range directionSlant range directionSlant rangeSlant range（斜距）（斜距）（斜距）（斜距）RangeRange（距离）（距离）（距离）（距离）Range Resolution（距离分辨率）When using pulse When using pulse compression techniquecompression technique脉冲压缩技术脉冲压缩技术脉冲压缩技术脉冲压缩技术 Antenna Flight directionAzimuth direction q D Range directionSlant range directionBR:Chirp bandwidthnExample:nPulse length=0.1 milli-seconds,look angle=30on Rr=0.1 x 10-3 x 3 x 108/2=15 kmnRr=Rr/sin(30o)=30 kmUsing range compression method:Azimuth Resolution（方位分辨率）Azimuth resolution of Azimuth resolution of real aperture radar real aperture radar 真实孔径雷达的方位真实孔径雷达的方位真实孔径雷达的方位真实孔径雷达的方位向分辨率向分辨率向分辨率向分辨率 Antenna Flight directionAzimuth direction q D Range directionSlant range directionSAR（合成孔径雷达）ooThrough the moving of antenna along a line,image a Through the moving of antenna along a line,image a scene for a number of timesscene for a number of times。通过沿着一条直线移动天线，通过沿着一条直线移动天线，通过沿着一条直线移动天线，通过沿着一条直线移动天线，对同一地物多次成像对同一地物多次成像对同一地物多次成像对同一地物多次成像ooSynthesize the multiple imaging data of a scene to one Synthesize the multiple imaging data of a scene to one imageimage。把同一地物的多次成像合成为一幅图像把同一地物的多次成像合成为一幅图像把同一地物的多次成像合成为一幅图像把同一地物的多次成像合成为一幅图像ooEquivalent to“enlarge”the antenna,forming a very long Equivalent to“enlarge”the antenna,forming a very long antenna and thus improving the azimuth resolution antenna and thus improving the azimuth resolution 等效等效等效等效于增大天线，形成一根很长的天线，从而改善分辨率于增大天线，形成一根很长的天线，从而改善分辨率于增大天线，形成一根很长的天线，从而改善分辨率于增大天线，形成一根很长的天线，从而改善分辨率Sketch Map（示意图）(From GlobeSAR program,CCRS)12Shift towards higher frequency34Shift towards lower frequencyDecomposition of Multiple Imaging（多次成像分解示意图）舒宁 等 1997Synthesis of Multiple Imaging（合成）oObjects experience illumination over a time interval oRecord and save the complete history of reflections（记录和保存了完整回波信号）oPermits reconstruction of the reflected signals（反射信号重建）oBased on the principle of Doppler frequency shift caused by the relative movement between the antenna and the target（依据多普勒频移原理）oBy tracing the frequency shifts and thus synthesising the corresponding echoes,the azimuth resolution can be sharpened(SAR focusing technique)（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)oFor ERS-1/2,a 10m antenna is used to synthesize a nearly 5 km antenna.oAbout 1000 radar images are used to get one SAR image.Renewed Azimuth Resolution(更新的方位分辨率)oSynthetic aperture radar（合成孔径雷达）Example:ERS-1/-2 SAR ResolutionAntenna length:L=10 m Typical range:Ground range resolution:Azimuth resolution:(Crimea,Ukraine)Real Aperture RadarSynthetic Aperture Radar5x14 km pixels4x20 m pixelsMassonnet and Feigl,1998The EndThank you!