# Bounding Volume Hierarchy-Assisted Fast SAR Image Simulation Based on Spatial Segmentation
## 1 Introduction
based on the CUDA platform used multi-thread parallel echo simulations on the targets constituting scene lattices and simultaneously generated master and slave images to obtain interferometric SAR raw data [18]. [PERSON] et al. proposed an effective simulation method for the raw echo signals of missile-borne SAR, which splits the scene into a number of data blocks along the azimuthal trajectory, and then uses GPU multi-threads to simulate each data block in parallel, which greatly accelerates the simulation speed of the raw echo signals [19]. [PERSON] et al. proposed an airborne bistatic SAR echo simulator based on multi-GPUs, which effectively improves the simulation echo simulation speed [20]. [PERSON] et al. used the existing SAR amplitude image as a backscatter coefficient matrix to bring it into the echo model and based it on the CUDA platform to implement the parallel echo simulation task for the used discrete units and subsequently proposed a local optimization algorithm to further improve the simulation efficiency [21; 22]. [PERSON] et al. proposed a time domain SAR raw data simulation method based on multi-GPUs, which cannot only simulate a large area of raw data through task division and scheduling but also improve the efficiency of current GPU-based algorithms through access conflict optimization and fine-grained parallel pipelines [23]. [PERSON] et al. designed and implemented a multi-FPGA parallel computing-based SAR real-time echo simulator to verify the correctness of the validity through the natural scene target imaging results of point targets [24]. [PERSON] et al. proposed a CPU/GPU collaborative SAR raw data simulation method in the time domain and conducted CPU/GPU collaborative simulation fine-grained task partitioning and scheduling experiments, which obtained a better-accelerated simulation result [25]. [PERSON] et al. briefly introduced the multi-mode synthetic aperture radar simulation framework and proposed a SAR raw data simulation method to assist the development strategy of the Gaofen-3 and its ground processing system [26]. Most of the above proposed methods are centered around a single aspect of SAR image simulation efficiency or fidelity and have achieved good simulation results. Most of the existing fast SAR image simulation methods choose to default the target backscatter coefficient to a fixed value within the corresponding synthetic aperture time under the plane wave assumption. Using the incident plane at the beam center as the phase reference plane cannot generate the real azimuthal Doppler phase history, which still needs to be phase corrected, but the amplitude of the fixed backscatter coefficient does not match the corrected phase. In addition, the methods mentioned above cannot effectively record the sidelobe signal within the 3 db beamwidth and do not fully consider the SAR phase reference system characteristics, simplifying the SAR echo simulation process, and can only meet the needs of low- or medium-resolution SAR image simulation applications. For high-resolution SAR image simulation, the Doppler bandwidth is large, the synthetic aperture time during the process of the target from entering the radar beam to leaving becomes longer, the azimuth angle of the incident EM wave changes, and the information contained in the echo signal, such as the amplitude, phase, polarization, frequency, and so on, is also changing all the time, and it increases the difficulty of reproducing the time-varying backscatter coefficient of the target that are dynamically recorded by pulse repetition time. Improving the simulation efficiency under the premise of ensuring the fidelity of SAR simulation images is still an urgent problem and a hot issue for never-ending iterative research. To address the aforementioned limitations, we propose a BVH-assisted fast SAR image simulation method based on spatial segmentation, which can effectively meet these demands.