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Point target response 
  
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power in dB 
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Figure 4. Increase of the resolution by doubling the bandwidth. The solid line represents the point target 
response of the transponder on the 45 MHz chirp giving a resolution of 3. m, the dashed line represents the 
response on the combined 90-MHz chirp giving a resolution of 1.5 m. 
3 INTERFEROMETRY 
3.1  Along-track interferometry (Moving Target Indication) 
Moving target indication (MTI) with SAR technology is complicated due to the movement of the platform which results 
in Doppler shifts for the stationary background clutter. Single beam MTI still can be performed and was demonstrated 
for PHARUS some time ago [van Rossum, 1999]. By processing a part of the Doppler spectrum outside the main lobe 
clutter (the stationary background) moving targets with velocities above 25 km/h can be detected. This technique was 
applied to a highway near Zoetermeer. In this application the part of the Doppler spectrum that was investigated yielded 
velocities around 120 km/h (the allowed maximum velocity on that highway) with a window of about 30 km/h. The 
moving targets were superimposed on the normal SAR image to give Figure 5. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 343