平直有耗地面上目标地波散射FDTD近一远场外推
AN FDTD NEAR TO FAR ZONE TRANSFORMATION FOR GROUND WAVE SCATTERING FROM OBJECTS ABOVE A FLAT EARTH
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摘要: 由平直有耗地面上垂直电偶极子产生地波场的解析解和互易原理,本文导出了用FDTD方法处理目标地波散射问题时的近一远场外推公式。在数值结果验证了该公式的正确性之后,对海上一金属半球的地波散射场进行了求解,并以此与李清亮等(1997)提出的工程应用方法相对比,考察了工程应用方法的适用性。
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关键词:
- 地波散射; FDTD方法; 近-远场外推
Abstract: A scheme of FDTD near to far zone transformation for ground wave scattering from objects above a flat earth is presented in this paper. With the equivalent principle, the equivalent electric and magnetic currents can be obtained from FDTD near field output boundaries. The fields radiated by these currents in the presence of a flat earth are then calculated using the reciprocity theorem and the known lateral wave formula of a vertical dipole(King, et al. 1992). Numerical results show excellent agreement between this scheme and analytical method. The feasibility of another approximation approach (Q.L.Li, et al. 1997) is also tested by this scheme. -
Li Qingliang, Ge Debiao, et al. Ground wave scattering from a ship on the sea. Proc. of 97 Int. Symp. on Radio Popagat., Qingdao, China, Aug. 1997, 134-136.[2]King R W P, Owens M, Wu T T. Lateral Electromagnetic Wave. New York: Springer-verlay, 1992,51-86.[3]Wong P B, Tyler G L, Baron J E, Simpson R A. A three-wave FDTD approach to surface scattering with application to remote sensing of geophysical surface. IEEE Trans. on Antennas and Propagt., 1996, AP-44(4): 504-514.[4]Demarest K, Huang Z B, Plumb R. An FDTD near-to far-zone transformation for scatterers buried in stratified ground. IEEE Trans. on Antennas and Propagt., 1996, AP-44(8): 1150-1157.[5]Harrington R F. Time-Harmonic Electromagnetic Fields. New York: McGraw-Hill, 1961, Chapter 3.[6]吴良超,汪茂光.复宗量菲涅尔函数的计算及其性质.电子科学学刊,1996, 16(6): 614-621.[7]Yee K S. Numerical solution of initial boundary value problems involving Maxwells equations in isotropic media. IEEE Trans. on Antennas and Propagt., 1966, AP-14(5): 302-306. -
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