Characterization and prediction of excess attenuation of microwave radio signals by vegetation forms

Depth dependence attenuation measurement was conducted at a uniformly planted orchard of horse chestnut trees to determine the excess attenuation of radio signals at 2 GHz and 11.2 GHz with increasing foliage depth in the signal path. The paper presents propagation models for predicting the excess attenuation experienced by radio signals propagated through paths obscured by vegetation forms. In support of the experimental study, a theoretical model based on the radiative energy transfer (RET) theory which considers the vegetation medium as a statistically homogeneous medium of discrete, lossy scatterers is used to assist in interpreting the experimental measurement results. The paper discusses the experimental measurement result and evaluates the performance of some of the available propagation models against measurement data.