Electromagnetic Scattering for Multiple Moving Targets Above/On a Rough Surface Using Multi-Dynamic-Octrees-Based SBR Algorithm.

For fast solving the electromagnetic scattering of multiple moving targets above or on a rough surface, the multi-dynamic-octrees-based shooting and bouncing ray (SBR) algorithm is proposed in the article. First, a local coordinate system (LCS) for each object is established that moves with targets in the geodetic coordinate system (GCS). The dynamic octree structure based on LCS is applied to keep the affiliation between facets and leaf nodes unchanged during target motion, which omits the reconstruction of the octree. Second, the emission plane determined by the incident direction is used for object projection. The scan line algorithm is improved and utilized to accelerate the elimination of shadows. Moreover, the ray-marching technique is employed to reduce the traversal of octree nodes for the high-order ray tracing on each object. For the ray tracing between different objects, the ray information is converted by the transformation matrix. Third, the scattering fields from targets and the surface (including the couple scattering between each other) are computed in LCS according to the illuminated facets. Then, the scattering fields are transformed to GCS, and the phase change caused by target movement is compensated. Finally, the total scattering of the composite model is acquired. Numerical results show the scattering of stationary and moving targets above/on the surface. The accuracy and efficiency of the proposed method are verified by comparing it with the multilevel fast multipole method (MLFMM) in FEKO and the traditional SBR method. Moreover, the electromagnetic scattering of multiple moving targets on the rough surface under different parameters is analyzed.