HORIZONTAL PROPAGATION THROUGH PERIODIC VEGETATION CANOPIES

Electromagnetic wave propagation through vegetation media has traditionally been modeled using random-media volume scattering approaches, such as the radiative transfer technique. Although such techniques have proven suitable for natural vegetation covers, experimental data suggest that a semideterministic technique is needed to model certain man-made vegetation canopies such as orchards, plantations, and row crops. A two-dimensional model has been developed to explain wave propagation through such canopies. The model is intended for media containing vertical cylinders, representing the stalks, and randomly oriented disks, representing the leaves. The formulation treats the canopy as a one-dimensional array of parallel stalks and a random distribution of leaves. The quasi-static approximation is used for computing scattering by the leaves which is valid only when the dimensions of the leaves are smaller than the wavelength. The model is a field approach, thereby accounting for all coherent, multiple interactions occurring in the canopy. The experimental component of this study includes measurements of the attenuation and phase shift patterns for horizontally and vertically polarized waves transmitted through a fully grown canopy of corn plants observed at 1.5 GHz. The model was found to provide excellent agreement with the experimental results.