In order to simulate the electromagnetic scattering of targets with thin-coating accurately, a conformal finite-difference timedomain (CFDTD) method based on effective constitutive parameters is presented in this paper. Two kinds of coating problems are considered. For a coated target with medium backing material, the CFDTD formulations on conformal cells are the same as those of the conventional FDTD, but the parameters in FDTD formulations are replaced by effective constitutive parameters to include the curved coating message of target. For a coated target with perfectly conducting (PEC) backing material, the contour-path integral is used to exclude the curved PEC part, and effective constitutive parameters are then introduced to include the coating message. The bistatic radar cross section (RCS) of coated spheres with medium backing material and with PEC backing material are computed, respectively, to validate the presented CFDTD scheme. The backscattering of a composite airfoil, which is made of radar absorbing material (RAM) and metal framework, and coated by fiberglass-reinforced plastics, is also analyzed to demonstrate the feasibility of presented scheme.
2. Shim, J. and H.-T. Kim, "Dominance of creeping wave modes of backscattered field from a conducting sphere with dielectric coatinging," Progress In Electromagnetics Research, Vol. 21, 293-306, 1999.
3. Kärkkäinen, M. K., "FDTD surface impedance model for coated conductors," IEEE Transactions on Electromagnetic Compatibility, Vol. 46, No. 2, 222-233, 2004.
4. Sheng, X.-Q., et al., "On the formulation of hybrid finite-element boundary-integral methods for 3D scattering," IEEE Trans. Antennas Propagat., Vol. 46, No. 3, 303-311, 1998.
5. Hu, J., et al., Computation of the RCS of 3-D coatinging conductor with arbitrary shape by using FMM and IBC, 2000 Proceedings of Antennas Propagation and EM Theory, 289-292, 2000.
6. Hu, X.-J., D.-B. Ge, and B. Wei, "Study on MCFDTD for3-D coated targets by using effective parameters," System Engineering and Electronics, Vol. 28, No. 11, 1652-1654, 2006.
7. Zheng, H.-X., X.-Q. Sheng, and E. K.-N Yung, "Computation of scattering from anisotropically coated bodies using conformal FDTD," Progress In Electromagnetics Research, Vol. 35, 287-297, 2002.
8. Gong, Z.-Q. and G.-Q. Zhu, "FDTD analysis of an anisotropically coated missile," Progress In Electromagnetics Research, Vol. 64, 69-80, 2006.
9. Strifors, H.-C. and G.-C. Gaunaurd, "Bistatic scattering by bare and coated perfectly conducting targets of simple shape," J. of Electromagn. Waves and Appl., Vol. 20, No. 8, 1037-1050, 2006.
10. Qiu, Z.-J., X.-Y. Hou, X. Li, and J.-D. Xu, "On the condition number of matrices from various hybrid vector FEM-BEM equations for 3-D scattering," J. of Electromagn. Waves and Appl., Vol. 20, No. 13, 1797-1806, 2006.
11. Hamid, A.-K. and F.-R. Cooray, "Radiation characteristics of a spheriodal slot antenna coated with isorefractive materials," J. of Electromagn. Waves and Appl., Vol. 21, No. 12, 1605-1619, 2007.
12. Rothwell, E.-J., "Natural-mode representation for the field reflected by an inhomogeneous conductor-backed material layer — TM case," J. of Electromagn. Waves and Appl., Vol. 21, No. 5, 569-584, 2007.
13. Yee, K.-S., "Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media," IEEE Trans. Antennas and Propagation, Vol. 14, No. 3, 302-307, 1966.
14. Taflove, A. and S.-C. Hagness, Computational Electrodynamics: The Finite-Difference Time-Domain Method, 3rd edition, Artech House, Norwood, MA, USA, 2005.
15. Jurgens, T.-G., A. Taflove, K.-R. Umashankar, and T.-G. Moore, "Finite-difference time-domain modeling of curved surfaces," IEEE Trans. Antennas and Propagation, Vol. 40, No. 4, 357-366, 1992.
16. Jurgens, T.-G. and A. Taflove, "Three-dimensional contour FDTD modeling of scattering from single and multiple bodies," IEEE Trans. Antennas and Propagation, Vol. 41, No. 12, 1703-1708, 1993.
17. Dey, S. and R. Mittra, "A modified locally conformal finitedifference time-domain algorithm for modeling three-dimensional perfectly conducting targets," Microwave and Optical Technology Letters, Vol. 17, No. 6, 349-352, 1998.
18. Yu, W.-H. and R. Mittra, "A conformal FDTD software package modeling antennas and microstrip circuit components," IEEE Antennas and Propagation Magazine, Vol. 42, No. 5, 28-39, 2000.
19. Li, Q.-L., H. Dong, W. Tang, and Y.-B. Yan, A simplified CFDTD algorithm for scattering analysis, 2003 6th International Symposium on Antennas Algorithm and Propagation and EM Theory Proceedings, 28-407, 2003.
20. Hu, X.-J., et al., "Conformal FDTD meshgenerating technique for objects with triangle-patch model," High Power Laser and Particle Beams, Vol. 19, No. 8, 1333-1337.
21. Kaneda, N., B. Houshm, and T. Itoh, "FDTD analysis of dielectric resonators with curved surface," IEEE Trans. Microwave Theory Tech., Vol. 45, No. 9, 1645-1649, 1997.
22. Yu, W.-H. and R. Mittra, "A conformal finite difference time domain technique for modeling curved dielectric surface," IEEE Microwave and Wireless Components Letters, Vol. 11, No. 1, 25-27, 2001.