7
SYSTEM MODEL AND DATA ACQUISITION OF SAR IMAGE
The two-dimensional target locations (or function) of radar image can be obtained by processing the target-reflected signals in both the cross-range (azimuth) and range directions. Range migration correction may be required for some applications. The principles and basic characteristics of radar image processing have been covered in a previous chapter in terms of Doppler frequency. This chapter describes radar image processing in the wavenumber domain. Section 7.1 describes the range radar imaging in the wavenumber domain; Section 7.2 discusses the cross-range radar imaging. Both the broadside SAR and the squint SAR are covered. Section 7.3 reviews data acquisition and the frequency spectrum of radar images.
7.1 SYSTEM MODEL OF RANGE RADAR IMAGING
7.1.1 System Model
Figure 7.1 shows a radar system configuration for range processing. The radar beam is assumed to be narrow enough in the azimuth direction that all targets are located at y = 0 and randomly distributed along the range (or x axis) direction.
Figure 7.1a is a 3D display of the radar system. The radar, moving at speed V along the y axis, is located at (0, 0, H) and emits a pulse at t = 0. The ground area covered by the radar pulse in the range direction will reflect the pulse wave after a short delay. The shortest distance to the ground is RN, and the longest distance is RF. The echo delay time due to the target at RN is t0 = (2RN/c) = (2x0/c sin θ). The echo delay time ...
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