Dominant lateral waves in the canopy layer of a four-layered forest

In this paper a forest model of four-layered geometry is utilized for the t heoretical analysis of radio wave propagation characteristics in the forest environment. Differing: from those reported in previous publications, the current paper considers a receiving: antenna that is located in the forest canopy layer instead of the trunk layer, and hence the results presented ar e not available elsewhere. Dyadic Green's functions in their eigenfunction expansion forms for the four-layered geometry are used at first to obtain a n exact integral representation of the radiated electric field in the canop y layer. The radiated electric field components due to an arbitrarily orien ted, small dipole in the trunk layer are then evaluated using: the saddle p oint technique and the branch cut integrations, leading to closed-form expr essions for the field. The total field is found to consist of the direct, t he reflected, and the lateral waves. Although both the lateral waves propag ating along the air-canopy and the trunk-ground interfaces play an importan t role in the propagation mechanism, only the lateral wave along the air-ca nopy upper interface dominates the total field in the far zone. Path loss o f the radio waves in the forest is computed numerically for both the vertic ally and the horizontally oriented dipoles.