Parallel Multilevel Fast Multipole Algorithm For Composite Targets

In recent years,various electromagnetic numerical algorithms have gradually matured.In spite of this,there are still many problems to be solved in the application of electromagnetic engineering,especially the calculation of the electromagnetic characteristics of complex electrically large-size targets.Multilevel Fast Multipole Algorithm(MLFMA)is a fast algorithm based on integral equations.Due to its high computational accuracy and low computational complexity,it is widely used in the simulation of electromagnetic scattering and radiation problems.In the calculation process of three-dimensional electromagnetic problems,the algorithm uses octree to perform spatial grouping of basis functions(weight functions),and at the same time uses interpolation algorithm to achieve spectral domain aggregation between layers.The complexity of MLFMA data structure seriously affects the scalability of its parallel algorithm,so the parallelization of the algorithm becomes one of the difficulties in the field of computational electromagnetics.Most scholars previously studied parallel MLFMA for metal or single dielectric models.There are few parallel MLFMA studies for metal mixed dielectric models or multi-dielectric models.This thesis first introduces the surface integral equations of multi-dielectric models,and then analyzes the applicable ranges of tangential,normal,and hybrid equations.Also,this thesis discusses the convergence of different integral equations by calculating metal and dielectric models.Further more,One asynchronous parallel MLFMA suitable for multidielectric model computation is studied.The advantages of asynchronous algorithms in load balancing and communication are discussed in comparison with synchronization algorithms.The parallel efficiency of the asynchronous algorithm is verified by calculating models of metal,single dielectric and multi-dielectric.Based on the theory above,a calculation method of the radiation characteristics of the covered antenna by combining the Higher Order Method of Moments(HOMo M)and MLFMA is presented.The hybrid method uses HOMo M and MLFMA respectively to calculate the antenna and the radome,and considers the coupling characteristics between the models by iterating the near field to ensure the calculation accuracy of the algorithm.Compared with the global solution of HOMo M,this hybrid method accelerates the computation speed and saves memory.It also avoids the non-convergence problem when using MLFMA to calculate a complex antenna,and provides an effective method for calculating the masked antenna model.