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

In this paper, a model with four layered media is utilized for the theoretical analysis of radiowave propagation in forest. The dyadic Green´s functions in their eigenfunction expansion forms for a four-layered geometry are used to derive the radiated electromagnetic fields in the canopy layer due to an arbitrarily oriented, small dipole located in the trunk layer. Saddle point technique and branch cut integration lead to closed form expressions for the field. Saddle points lead to the representations of both direct and multi-reflected waves while the integrals along branch cuts give lateral waves along various interfaces. It is also noted that the lateral waves along the air-canopy interface dominates the total electric field. Path loss in the forest is computed numerically for different orientation of the dipole, using these dominant lateral waves