volume | PIER Journals

Abstract

Numerical simulations of emission for two-dimensional randomly rough surfaces with an inhomogeneous layered medium are presented. The inhomogeneous layered medium is modeled by a generalized n-layered stratified media. The numerical method was adopted from the physics-based two-grid method (PBTG). To ensure the strict accuracy requirement while to relief the memory and CPU resources, the PBTG in conjunction with the sparse-matrix canonical grid method (SMCG) was used in this paper. In so doing the reflected terms of the dyadic Green's function that accounts for layered media were added into the integral equations governing the surface tangential fields. Since the reflected part of the dyadic Green's function does not contain any singularity, the normal components of the fields remain the same as in the case of homogeneous surfaces. It was found that the elements of Green's tensor are only important to the near-field since they decay very fast as spatial distance goes beyond a few wavelengths. The resulting integral equations are then solved by the Method of Moment (MoM). Comparisons between the inhomogeneous and the homogeneous rough surfaces suggest that the presence of the inhomogeneous layered medium has non-negligible contributions to emission, depending on the dielectric gradient and is polarization dependent.

1. Tsang, L., J. A. Kong, and R. T. Shin, Theory of Microwave Remote Sensing, John Wiley & Sons, 1985.

2. Chew, W. C., Waves and Fields in Inhomogeneous Media, IEEE Press, 1995.

3. Fung, A. K. and M. F. Chen, "Emission from an inhomogeneous layer from a rough surface," Radio Science, Vol. 16, 289-298, 1981.

4. Wang, J. R. and B. J. Choudhury, "Remote sensing of soil moisture content over bare fields at 1.4 GHz frequency," J. Geophys. Res., Vol. 86, 5277-5282, 1981.

5. Tsang, L. and R. W. Newton, "Microwave emissions from soils with rough surfaces," J. Geophy. Res., Vol. 87, No. 11, 9017-9024, 1982.

6. Wang, J. R., P. E. O'Neill, T. J. Jackson, and E. T. Engman, "Multi-frequency measurements of the effects of soil moisture, soil texture and surface roughness," IEEE Trans. Geosci. Rem. Sens., Vol. GE-21, 44-51, 1983.

7. Mo, T., T. J. Schmugge, and J. R. Wang, "Calculations of the microwave brightness temperature of rough soil surfaces: bare field," IEEE Trans. Geosci. Remote Sensing, Vol. GE-25, No. 1, 47-54, 1987.
doi:10.1109/TGRS.1987.289780

8. Shi, J., J. Dozier, and H. Rott, "Snow mapping in alpine regions with synthetic aperture radar," IEEE Transactions on Geoscience and Remote Sensing, Vol. 32, No. 1, 152-158, 1994.
doi:10.1109/36.285197

9. Shi, J., J. Wang, A. Hsu, P. O'Neill, and E. T. Engman, "Estimation of bare surface soil moisture and surface roughness parameters using L-band SAR image data," IEEE Transactions on Geoscience and Remote Sensing, Vol. 35, No. 5, 1254-1266, 1997.
doi:10.1109/36.628792

10. Fuks, I. M. and A. G. Voronovich, "Wave diffraction by rough interfaces in an arbitrary plane layered medium," Waves in Random Medium, Vol. 10, 253-272, 2000.
doi:10.1088/0959-7174/10/2/304

11. Johoson, J. T., "Thermal emission from a layered medium bounded by a slightly rough interface," IEEE Trans. Geosci. Remote Sensing, Vol. 39, No. 2, 368-378, 2001.
doi:10.1109/36.905245

12. Chen, K. S., T. D. Wu, L. Tsang, Qin Li, and J. C. Shi, "The emission of rough surfaces calculated by the Integral equation method with a comparison to a three-dimensional moment method simulations," IEEE Trans. Geoscience and Remote Sensing, Vol. 41, No. 1, 90-101, 2002.
doi:10.1109/TGRS.2002.807587

13. Pelosi, G. and R. Coccioli, "A finite element approach for scattering from inhomogeneous media with a rough interface," Waves in Random Media, Vol. 7, 119-127, 1997.
doi:10.1088/0959-7174/7/1/008

14. Giovannini, H., M. Saillard, and A. Sentenac, "Numerical study of scattering from rough inhomogeneous films," J. Opt. Soc. Am, Vol. 15, No. 5, 1182-1191, 1998.

15. Tsang, L., C. H. Chan, and K. Pak, "Backscattering enhancement of a two-dimensional random rough surface (three-dimensional scattering) based on Monte Carlo simulations," J. of Optical Society of America A, Vol. 11, No. 2, 711-715, 1994.

16. Johnson, J., L. Tsang, R. Shin, K. Pak, C. H. Chan, A. Ishimaru, and Y. Kuga, "Backscattering enhancement of electromagnetic waves from two-dimensional perfectly conducting random rough surfaces: A Comparison of Monte Carlo simulations with experimental data," IEEE Trans. Antennas Propagat., Vol. 44, 748-756, 1996.
doi:10.1109/8.496261

17. Tsang, L. and Q. Li, "Numerical solution of scattering of waves by lossy dielectric surfaces using a physics-based two-grid method," Microwave Opt. Technol. Lett., Vol. 16, No. 6, 356-364, 1997.
doi:10.1002/(SICI)1098-2760(19971220)16:6<356::AID-MOP10>3.0.CO;2-Z

18. Li, Q., C. H. Chan, and L. Tsang, "Monte-Carlo simulations of wave scattering from lossy dielectric random rough surfaces using the physics-based two-gird method and canonical grid method," IEEE Trans. Antennas Propagat., Vol. 47, No. 4, 752-763, 1999.
doi:10.1109/8.768816

19. Tsang, L., J.-H. Cha, and J. R. Thomas, "Electric fields of spatial Green's functions of microstrip structures and applications to the calculations of impedance matrix elements," Microwave and Optical Technology Letters, Vol. 20, No. 2, 90-97, 1999.
doi:10.1002/(SICI)1098-2760(19990120)20:2<90::AID-MOP3>3.0.CO;2-7

20. Tsang, L., J. A. Kong, K. H. Ding, and C. O. Ao, Scattering of Electromagnetic Waves, Volume II: Numerical Simulations, 2001.

Dr. Kunshan Chen

Professor Leung Tsang

Prof. Jian-Cheng Shi