The Application Of Fdtd And Pstd Hybrid Algorithm In Low Frequency Ground-wave Propagation

Low frequency ground-wave signal is widely used in long distance navigation, timing and communication because of its stable transmission, low attenuation, strong diffraction capability and long distance of propagation. However, by the influence of the terrain fluctuation change,the inhomogeneous distribution of the objects and the space-time change of the atmospheric environment, the propagation velocity, direction and phase of the actual low frequency ground-wave signal are different from those in the vacuum. Therefore, high precision and rapid prediction method for studying the propagation characteristics of low frequency ground-wave in complex environment is the key to improve the accuracy of low frequency ground wave navigation and timing system.The existing Finite-Difference Time-Domain method (FDTD) can simulate the propagation process of the actual signal, but there are some problems such as large numerical dispersion error and excessive computer memory consumption in long distance application.Meanwhile, Pseudo-spectral Time Domain Method (PSTD) can handle electrically large electromagnetic computing problems, but it is difficult to deal with problems of complex structure and medium mutations. Aiming at the above problem, this paper proposes a numerical prediction method of "FDTD + PSTD" by combining frequency domain and space domain. The hybrid algorithm divides the propagation area, and combines the advantages of FDTD method and PSTD method to realize the high precision and fast prediction of low frequency ground-wave propagation performance. Specific research includes:Firstly, this paper starts from the theory of the FDTD and PSTD, and the realization process of the two algorithms is deduced and verified by simulation. Meanwhile, characteristics of each algorithm are compared and analyzed. And secondly, in view of the low frequency ground-wave propagation problems, the feasibility and existing problems of the FDTD method and PSTD method are analyzed when applied to the problem Thirdly, based on the above analysis results, a numerical prediction method of "FDTD+ PSTD" by combining frequency domain and space domain is proposed. And studies are carried out from the regional division,the combination of mode, the amount of field iteration, grid division, the junction of the field transfer and other aspects. At the same time, the simulation validates the effectiveness of the hybrid algorithm under different ground model. Finally, the hybrid algorithm is applied to the near-field effect of the antenna,and the influence of the ground condition on the radiation characteristics of the antenna is simulated and analyzed.The simulation results show that under certain prediction accuracy, the hybrid algorithm is 3?4 times faster than FDTD and 1?2 times less than FDTD in memory consumption. At the same time, the ground conditions of the near field area will have a great influence on the radiation characteristics and the phase center of the antenna. Therefore, the research results of this paper will provide technical support for high precision prediction of long distance, large area low frequency ground-wave propagation performance and engineering realization.