We study the radio wave propagation at VHF frequencies in a forested environment using a three-layer anisotropic slab model. The analytical solution to the slab model is implemented numerically to generate broadband data. The data are then transformed into the time domain. The various propagation mechanisms including the direct wave, the lateral wave, the multi-reflected slab waves and the multi-bounce lateral waves are investigated based on their respective times-of-flight. Our results show that the dominant propagation mechanisms are highly dependent on the effective permittivity and conductivity of the forest layer. We then utilize the numerical solution to extract the effective medium parameters of the forest based on the published measurement data of Hicks et al. Good agreement between the fitted model and the measurement data is achieved. The extracted effective permittivity and conductivity of the forest layer show considerable anisotropy and frequency dependence.
2. Sachs, D. L. and P. J. Wyatt, "A conducting slab model for electromagnetic propagation within a jungle medium," Radio Sci., Vol. 3, 125-134, 1968.
3. Dence, D. and T. Tamir, "Radio loss of lateral waves in forest environments," Radio Sci., Vol. 4, 307-318, Apr. 1969.
4. Tamir, T., "Radio wave propagation along mixed paths in forest environment," IEEE Trans. Antennas Propagat., Vol. 25, 471-477, Jul. 1977.
5. Brown, G. S. and W. J. Curry, "A theory and model for wave propagation through foliage," Radio Sci., Vol. 17, 1027-1036, Sept./Oct. 1982.
6. Cavalcante, G. P. S., D. A. Rogers, and A. J. Giardola, "Analysis of the electromagnetic wave propagation in multilayered media using dyadic green's function," Radio Sci., Vol. 17, 503-508, May/Jun. 1982.
7. Cavalcante, G. P. S. and A. J. Giardola, "Optimization of radio communication in media with three layers," IEEE Trans. Antennas Propagat., Vol. 31, 141-145, Jan. 1983.
8. Matthaeis, P. D. and R. H. Lang, "Microwave scattering models for cylindrical vegetation components," Progress In Electromagnetics Research, 131-153, PIER 40, 2003.
9. Huang, E. X. and A. K. Fung, "Electromagnetic wave scattering from vegetation with odd-pinnate compound leaves," Journal of Electromagnetic Waves and Applications, Vol. 19, No. 2, 231-244, 2005.
10. Li, L. W., T. S. Yeo, P. S. Kooi, M. S. Leong, and J. H. Koh, "Analysis of electromagnetic wave propagation in forest environment along multiple paths," Journal of Electromagnetic Waves and Applications, Vol. 13, 1057-1059, 1999.
11. Sarabandi, K. and I. S. Koh, "Effect of canopy-air interface roughness on HF-VHF wave propagation in forest," IEEE Trans. Antennas Propagat., Vol. 50, No. 2, 111-121, Feb. 2002.
12. Li, L. W., J. H. Koh, T. S. Yeo, M. S. Leong, and P. S. Kooi, "Cylindrical vector eigenfunction expansion of green dyadics for multilayered anistropic media and its application to four-layered forest," IEEE Trans. Antennas Propagat., Vol. 52, 466-477, Feb. 2004.
13. Whale, H. A., "Radio propagation through New Guinea rain forest," Radio Sci., Vol. 3, 1038, Oct. 1968.
14. Tewari, R. K., S. Swarup, and M. N. Roy, "Radio wave propagation through rain forests of India," IEEE Trans. Antennas Propagat., Vol. 38, 433-449, Apr. 1990.
15. Rogers, R. L. and H. Ling, "Extended line-of-sight communications for unattended ground sensors,", Final Report, DARPA Unattended Ground Sensor Program, Dec. 2005.
16. Hicks, J. J., A. P. Murphy, E. L. Patrick, and L. G. Sturgill, "Tropical propagation research,", Research and Engineering Dept., Atlantic Research Corp., Alexandria, Va., Nov. 1969.
17. Ling, H. and J. Moore, "Scattering by conductor-backed dielectric gaps,", Rome Air Development Center Tech. Report, F49620-88-C-0053, Sep. 1990.
18. Hagn, G. H. and H. W. Parker, "Feasibility study of the use of open-wire transmission lines, capacitors and cavities to measure the electrical properties of vegetation,", Stanford Research Institute Tech. Rept. 13, Aug. 1966.
19. Parker, H. W. and W. Makarabhiromya, "Electric constants measured in vegetation and in Earth at five sites in Thailand,", Stanford Research Institute Special Tech. Rept. 43, Menlo Park, California, 1967.
20. Pounds, D. J. and A. H. LaGrone, "Considering forest vegetation as an imperfect dielectric slab,", Electric Engrg. Research Lab., University of Texas, Austin, Tech. Rept. 6-53, May 1963.
21., "IEEE guide for measurements of electromagnetic properties of Earth media,", IEEE Std. 356-2001, IEEE Antennas Propagat. Soc., Jun. 2002.