Electromagnetic wave attenuation for propagation through a forest belt

Some theoretical and experimental results on the attenuation of electromagnetic wave propagating through a forest belt are presented. A theoretical model proposed for evaluating the wave field amplitude is based on the Kirchhoff-Fresnel principle. It concerns with both the horizontal and vertical polarizations, relevant wave diffraction problems, being solved in the two-dimensional approximation. An experimental study was carried out tit the frequency of 0.6 GHz. The transmitter Was located in front of the belt edge at the distance of 25 m, being positioned at the heights of 5, 11, and 16 m above the ground, while the receiver, placed at the height of 2 m, is-as being moved through the forest belt and further on to the point located at the distance of 60-120 in from the rear edge of the forest belt. The latter had about 100 in in width, and was situated 150 km to the northwest from the city of Ulan-Ude near Baikal lake, being consisted mostly of the birch and cedar trees. The height and diameter of trees varied from 10 to 15 m and from 0,15 to 0,25 m, respectively, with the average density of those being of 0.3 trees/m(2). All measurements were conducted in August 2003. The magnitude of wave field is-as found to attenuate with the distance from transmitter as an exponential function. In the case of vertical polarization, the rates of attenuation were measured of 0.2-0.5 dB/m and of 0.0-5-0.08 dB/m, as related to the wave paths located inside the forest belt and behind it, respectively. As expected, the rate of attenuation for the wave with horizontal polarization was found 0.1-0.15 dB/m below that relating to the vertical polarization. Finally, the relative contributions of specific partial components to the total amplitude of wave field were analyzed, using the theoretical model proposed.