| With the development of marine resources and the importance of its strategic position, the study on the electromagnetic scattering characteristics of rough sea surface is becoming more and more important. Due to the complicated sea environment, sea clutter brings the interference for radar target detection, capture and guidance, and so on. Therefore, the analysis of different sea state under different conditions of electromagnetic scattering brooks no delay. In this paper, the fast multipole method(FMM) and parallel algorithm based on the method of moment(MOM) are used to study the electromagnetic scattering of the breaking wave at low grazing angles. The main accomplishments are as follows:1. The basic theory of electromagnetic scattering from rough surfaces is briefly introduced, including the radar equation, the double Debye model of the sea water dielectric constant, and the choice of the parameters of the incident cone wave. Using Monte Carlo method to simulate the generation of PM sea spectrum, combined with the LONGTANK breaking wave model, the geometrical model of the breaking wave is established.2. The basic principle of the method of moment(MOM) and fast multipole method(FMM) is introduced, and the fast multipole method is used to study the electromagnetic scattering from rough sea surface at different angles. In different polarization, different incident angles, different frequencies and different wind speeds, the electromagnetic scattering coefficient of the conductor surface and the dielectric sea surface changes with the scattering angle.3. The parallel algorithms based on MPI and Open MP have been introduced to compute the electromagnetic scattering from rough sea surface. The specific parallel algorithm acceleration process is given and calculation results and time of two parallel algorithms are compared with the MOM and FMM, which verifies the efficiency and accuracy of the parallel algorithm and highlights the advantages of parallel algorithm in solving matrix.4. The FMM and parallel algorithms have been applied to the electromagnetic scattering calculation of the breaking wave. The electromagnetic scattering in different stages of the formation of the breaking wave has been analyzed and discussed. According to thevariation of electromagnetic scattering with the incident angle, the multipath effect is not apparent and the VV polarization is larger than the HH polarization in the early stage of breaking wave. In the middle of breaking wave generation, the waves began to appear, VV polarization reduced and HH polarization enhanced. With the evolution of the sea surface, there are complete comber and obvious sea spike phenomenon appearing late in the breaking wave formation. HH polarization and VV polarization difference becomes larger. |
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