Study On SBR Algorithm For EM Scattering Of Ship Objects

The research of electromagnetic scattering characteristics of ship objects has important application in the shape of the ship design and the sea environmental monitoring. Generally ship is a kind of electrically large objects, and Shooting and Bounding Rays(SBR) method is a kind of high frequency algorithm which is very suitable to calculate electrically large objects, so this thesis adopts the SBR method which based on KD-tree algorithm to research electromagnetic scattering characteristics of a variety of ship objects. At the same calculation precision, the KD-tree-Based SBR method can locate the final intersecting facet more rapidly than the trad itional SBR technique, and it can enhance the calculation efficiency of electrically large complex targets more obviously, so can greatly reduce the cycle of model research. By calculating the Radar Cross Section(RCS) of ship objects in the same frequency but different angle and same angle but different frequency, analysis of the electromagnetic scattering intensity of each structure of the ship object, and presents some of the ways to reduce the RCS. The main work of the thesis is as follow:1. Traditional SBR method is implemented. Traditional SBR method is a kind of hybrid algorithm of geometrical optics and physical optics method, it is to overcome the problem that the geometrical optics method cannot calculate arbitrary geometry and solves the problem that the physical optics method can only calculate single scattering, so the traditional SBR method has been widely used. The RCS of dihedral angle, cube, and combination objects are calculated by using traditional SBR method, and compared with the simulation results of FEKO, validate the correctness of the algorithm.2. KD-tree SBR method which based on clues is implemented. Though the electrically large targets can be calculated by traditional SBR method, the computation efficiency of traditional SBR method is not high, so it is difficult to meet the needs of the scientific research. It is because traditional SBR method evenly divided tube grid, so it will produce a large number of rays and have a large number of invalid judgment in the process of rays and triangle facets intersection, so the algorithm is inefficient. KD-tree SBR method which based on clues with the method of constructing bounding box, triangle facets are surrounded in AABB bounding boxes, the box is the node of the KD-tree, and then add clues to each leaf node. So you can avoid the rays from the root node to traverse the KD tree. The target bounding box rays first be found, and then the ray find the ray intersection with the triangle facet in the box. It can avoid a lot of invalid intersection and greatly improve the execution efficiency of the algorithm. The RCS of dihedral angle, trihedral angle, and simple ship objects are calculated by using the KD-tree SBR method, and compared with the simulation results of FEKO, verify the correctness of the algorithm, and then compared with traditional SBR method, verified the efficiency of the algorithm.3. The RCS of assault craft, patrol boats, fishing boats and destroyer ship targets are calculated by the KD-tree SBR method based on clues, electromagnetic scattering characteristics of them are analyzed in the same frequency but different angle and same angle but different frequency. One type of ship model are presented, and conducted two optimization to it, contrasts the radar cross section between them under different angles, analyses the optimization results, optimize the conclusion is given, compared the maximum, average and the probability greater than the threshold value of RCS under different attitude angles among them, this thesis analyses the optimization results and gives the optimization conclusion.