2.2 Numerical results 00和-402002406B1 00和0402002408留10 Fig. Imaging results for a target in the shape of circle, r 20m 防科学时太季 A Direct Numerical Imaging Method 19 National University of Defense TechnologyA Direct Numerical Imaging Method 2.2 Numerical Results 19 Fig. Imaging results for a target in the shape of circle, r = 20m