Vegetation attenuation of microwaves - measurements and model evaluation

Abstract

The aim of this report is to analyse measurements of vegetation attenuation at 18GHz and 38GHz. The transmitter and the receiver are both located in the forest in such a way that the main part of the radio wave propagate through the grove. Experiments are performed with groves of pine, spruce and trees in-leaf and off-leaf. In-leaf groves give the highest median attenuation while groves of pine give the lowest median attenuation. Evaluation of how five current models predict the measured attenuation of the different vegetation types is performed. The result is a set of preferable models for each of the vegetation types. Analysis of the received signal-level in time shows that the estimated distribution approaches a Rayleigh distribution when the standard deviation of the time-series is above 5dB. Exploration of the received signal-level in space exposes that the estimated distribution resembles a Rayleigh distribution when the standard deviation of the space-series is greater than 6dB.