Principles of Modern Radar - Volume 2 1891121537

7.5 Range Migration Algorithm 309Along-Track (m)Collection Geometry−25−20−15−10−50510152025−10 −5 0 5 10 15 20 25 30 35 40 45 50Cross-Track (m)FIGURE 7-47Simulated UHFgeometry.• Resolution = 0.2 m (both dimensions)• Range to scene center = 30 m• Scene size = 10mby20mThis same ultra high frequency (UHF) example was used in [1] to demonstrate backprojectionimage formation.The RDA image in Figure 7-48a is well focused for the three scatterers correspondingto the PSR reference range in the middle of the swath. However, one does not need to moveup-range or down-range very far before cross-range defocusing becomes unacceptable.In contrast, all five scatterers are well focused in the RMA image in Figure 7-48b, whichcompares favorably to the backprojection image in [1].Figure 7-49 shows the data in the 2-D frequency domain, with k u replaced by k x and ωrescaled to k r . The triangular support of the data is typical for wideband collections and isa consequence of the higher Doppler frequencies (larger values of k x ) supported by higherCrossrange (m)RDA, Full PSA SAR (dB)−5−4−3−2−1012345−5 −4 −3 −2 −1 0 1 2 3 4 5Downrange (m)0−5−10−15−20−25−30−35−40−45−50Crossrange (m)RMA (Omega-k) SAR (dB)−5−4−3−2−1012345−5 −4 −3 −2 −1 0 1 2 3 4 5Downrange (m)FIGURE 7-48 Simulated UHF imagery using full-PSR and (a) RDA, and (b) RDA with Stoltinterpolation (RMA).0−5−10−15−20−25−30−35−40−45−50