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1、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 direction
2、Azimuth direction q D Range directionSlant range directionrRRpulse oflength light of velocity where)sin2/(qppr ccRpulse oflength light of velocity where2/ppr ccRRange Resolution （距离分辨率） Antenna Flight directionAzimuth direction q D Range directionSlant range directionrRRqsin2RrBcR BR : Chirp bandwid
3、thnExample: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:m 20)30sin(1055.152103sin268qRrBcRAzimuth Resolution（方位分辨率）antenna physical oflength wavelength rangeSlant where/D RDRR! !km! 5 . 4 R ,10D0.056m,
4、 km, 800R ：ERS1/2 of Examplem Antenna Flight directionAzimuth direction q D Range directionSlant range directionRRSAR（合成孔径雷达）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 Mu
5、ltiple 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 a
6、nd 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
7、 km antenna.oAbout 1000 radar images are used to get one SAR image.Renewed Azimuth Resolution(更新的方位分辨率)DRRDD RDRRgenerally ,antenna dsynthesize oflength wavelength rangeslant where/2/ resolutionazimuth renewed get the wetrip,round ion theconsiderat takingand , into InsertingDRRDRDoSynthetic aperture
8、 radar（合成孔径雷达）Example: ERS-1/-2 SAR ResolutionAntenna length: L=10 m Typical range:km 85323cos/satHRm 25)23sin(1055.152103sin268qRrBcRGround range resolution:km 510/056.0853000DRRAzimuth resolution:m 52/102DR(Crimea, Ukraine)Real Aperture RadarSynthetic Aperture Radar5x14 km pixels4x20 m pixelsMassonnet and Feigl, 1998The End