At the first step, the grid cell is set to . Figure 6(a) gives the initial image recovered via the correlation method based on the grid cell. There are three distinct pixels in Fig. 6(a). The positions corresponding to three pixel centers are derived: (0,0), (300, 300), and (, ). It denotes that targets are included in the three square areas of size. To be prudent, we expand the size to . That is, the new subareas are three square areas of , whose centers are (0,0), (300, 300), and (,), respectively. Then, the grid cell is reset to , based on which the new three subareas are redivided. Then, target scattering coefficients can be recovered via the parameterized method with respect to the three subareas, as shown in Figs. 6(b) and 6(c). In this case, the grid-cell number needed to be considered in the parameterized method is decreased from to 4800 (herein, is the grid-cell number for a target area when we keep a grid cell), which greatly reduces the complexity burden. For the sake of simplicity, the following examples directly show the imaging results after selecting the target subareas.