合成孔径雷达概念

(Courtesy: CCRS)
(Courtesy: CCRS)
For ERS-1/2, a 10m antenna is used to synthesize a nearly 5 km antenna. About 1000 radar images are used to get one SAR image.
c 3 ×108 Rr = = = 20 m 6 o 2 BR sin θ 2 × 15.55 × 10 sin(30 )
Azimuth Resolution（方位分辨率）
Azimuth resolution of real aperture radar 真实孔径雷达的方位 向分辨率
Rβ = Rλ / D where R −Slant range λ − wavelength D − length of physical antenna Exam of ERS1/2： ple
Based 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）
By 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）
Rλ = 853000 × 0.056 / 10 ≈ 5 km D D ′ Rβ = = 10 / 2 = 5 m 2 Rβ =
Real Aperture Radar
Synthetic Aperture Radar
(Crimea, Ukraine)
5x14 km pixels
Massonnet and Feigl, 1998
4x20 m pixels
~The End~
Thank you!
Renewed Azimuth Resolution (更新的方位分辨率)
Synthetic aperture radar（合成孔径雷达）
′ Rβ = Rλ / D′ where R − slant range
λ − wavelength
D′ − length of synthesize d antenna , generally D′ = Rβ = Rλ D
θ
D
R
Rβ
R ≈ 800 km , λ = 0ቤተ መጻሕፍቲ ባይዱ056m , D =10m, ⇒ Rβ ~ 4.5 km !! !
SAR（合成孔径雷达）
Through the moving of antenna along a line, image a scene for a number of times。通过沿着一条直线移动天 times。 线，对同一地物多次成像 Synthesize the multiple imaging data of a scene to one image。 image。把同一地物的多次成像合成为一幅图像 Equivalent to “enlarge” the antenna, forming a very long antenna and thus improving the azimuth resolution 等效 于增大天线，形成一根很长的天线， 于增大天线，形成一根很长的天线，从而改善分辨率
D
τ p − length of pulse
θ
Range（距离） Range（距离）
Rr = cτ p /(2sin θ ) where c − velocity of light
R
τ p − length of pulse
Rr
Range Resolution （距离分辨率）
When using pulse compression technique 脉冲压缩技术
Sketch Map（示意图）
(From GlobeSAR program, CCRS)
Decomposition of Multiple Imaging （多次成像分解示意图）
1
3
2
4
舒宁 等 1997
Synthesis of Multiple Imaging（合成）
Objects experience illumination over a time interval Record and save the complete history of reflections （记录和保 存了完整回波信号） Permits reconstruction of the reflected signals （反射信号重建）
D
c Rr = 2 BR sin θ
θ
R
BR : Chirp bandwidth
Rr
Example: Pulse length = 0.1 milli-seconds, look angle = 30o R’r = 0.1 x 10-3 x 3 x 108/2 = 15 km Rr = R’r/sin(30o) = 30 km Using range compression method:
Azimuth 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）
Slant range（斜距） range（斜距）
′ Rr = cτ p / 2 where c − velocity of light
Antenna length: L=10 m Typical range: R = Hsat / cos 23o = 853 km Ground range resolution:
c 3×108 Rr = = = 25 m 6 o 2BR sin θ 2×15.55×10 sin 23 ) (
Azimuth resolution:
第二章. Concept of SAR（合成 孔径雷达概念）
Radar Resolution（分辨率）
Range 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。
′ Inserting D′ = Rλ D into Rβ , and taking considerat ion the round trip, we get the renewed azim resolution uth ′ Rβ = D/ 2
Example: ERS-1/-2 SAR Resolution