## 4 Simulation Results and Discussion
### Simulation 2
Moreover, we utilized the small square line to express the inverse results with clutter and noise backgrounds with 10 s pulse accumulation. It shows that target peaks can be recognized from clutter and noise backgrounds with the proposed inverse method. In the other situation, since we have estimated the target information, we can acquire rough target distance ranges and reverse them using the range inverse method 2. Figure 15 shows the range inverse results based on target estimation information, where ship 2 can notably be expressed more completely and accurately than with method 1. Figure 14: Range inversion results of 3 ship targets under the detection of BDS satellite 3 with range inversion method 1: (a) ship 1; (b) ship 3; (c) left part of ship 2; (d) right part of ship 2. Starting from the two dimensions of Doppler and range, Figure 16 plots the DDM results of three ship targets under the detection of the B3I signal of satellite 3, where pictures (a) and (b) express whether the results consider clutter and noise. In Figure 16a, combined with target peak identification and target range inverse results, we found that the highlight groups were target 1, target 3, and target 2 from left to right. The ship targets can be detected as several highlights with a range resolution of near 30 m and a Doppler frequency resolution of approximately 8 Hz. Due to the high speed of the receiver and different received angles, the targets' Doppler frequency varies in the range of 400 Hz, and there are 8 Hz offsets in the scattered point in a target. After introducing clutter and noise backgrounds, Figure 16b shows the detection results with clutter distribution, as shown in Figure 7, with 10 s pulse accumulation. We found a clutter highlight group near the 0 Hz Doppler channel with a normalized amplitude of 0.6. In the range dimension, a few clutter peaks overlapped target 1, which protected the detection of target 1 from clutter influence. Some cluttered peaks overlapped target 2 and target 3, but the cluttered peaks are small and dispersed, which reduces the influence of the detection of the two targets. Moreover, the cluttered strong scatter point does not overlap in the simulation, supporting better detection results for the signal process. This situation has a large probability of overlapping since the scattering intensity of sea clutter is random. Figure 16: DDM detection results of 3 ship targets under the detection of satellite 3: (**a**) without clutter and noise influence; (**b**) with clutter background. Figure 15: Range inversion results of 3 ship targets under the detection of BDS satellite 3 with target estimation information by range inversion method 2: (**a**) ship 1; (**b**) ship 2; (**c**) ship 3. Figures 12-16 show the one-dimensional range image Doppler compensation results, one-dimensional range image target peak identification results, range inverse results, and DDM results of three ship targets in simulation 2, which verify that multiple fetched ship targets can be detected with better strength using the MDTC method with noise and sea clutter backgrounds in a 10 s accumulation, and the ship RCS distribution structure can be further acquired by the proposed target peak identification method and range inversion method.