Study Of Conformal FDTD Algorithm For Electromagnetic Scattering By Complex Targets

Finite Difference Time Domain method is one of numerical algorithm which iswidely used EM wave simulation. The mathematical process of this algorithm is arelatively simple. Combining with the Fourier transform one can get the broadbandelectromagnetic message in one FDTD computation. In addition, the ladderapproximation error also influences the accuracy of FDTD computation. In this paper,the conformal method is used to improve the FDTD modeling and calculation accuracy.For curved surface of medium, the effective values of permittivity and electricconductivity for E-field samples on conformal cells are calculated by weighted-lengthof medium and free space on the edges. The effective values of permeability andequivalent magnetic loss for H-field samples are however calculated by weighted-areaof medium and free space on the flanks. The stair casing errors caused by conventionalFDTD method in simulating curved surface is reduced by introducing effectiveconstitutive parameters on the boundary of targets, and the computational precision ofFDTD method is improved effectively. For a coated target with medium backingmaterial, the CFDTD formulas about E-field and H-field samples on conformal cellsare the same as those of conventional FDTD, but the constitutive parameters inCFDTD formulas are replaced by effective parameters to include the curved coatingmessage. The effective values of permittivity and electric conductivity for E-fieldsamples on conformal cells are calculated by weighted-length of backing medium,coating and free space. At last, the scattering characteristic of complex object isanalysis by the CFDTD method. By comparing the obtained conformal FDTDalgorithm than the conventional FDTD algorithm accuracy has been improved.