Two-Dimensional Models of a Tree in the Propagation of 920-MHz Band Radio Wave

Two-dimensional FDTD analysis of the radio wave propagation characteristics of 920-MHz band is performed, in which two models of a tree are examined. Model 1 uses a pattern set in which one cell out of n
²
cells is as a leaf and (n
²
– 1) cells as air. In model 2, the entire tree is considered as a homogeneous dielectric object that has electrical characteristics intermediate between leaves and air whose permittivity and conductivity are set to 1 / n
²
of those of leaves. The analysis area is such that a tree and the ground are seen from the side. The loss characteristic for the two models, inhomogeneous and homogeneous, have been compared. From the simulation results, the same propagation characteristics are obtained for model 1 and model 2 with horizontal polarization when comparing the propagation loss characteristics at the observation point 70 wavelengths away from the excitation in both models. On the other hand, for vertical polarization, equivalent propagation characteristics are obtained between model 1 and model 2 with the quadruple density.