Microwave Propagation in Vegetation Media

Attenuation of microwave signals at 11.2 GHz through a conifer wood and a regularly planted apple orchard is investigated. The measured attenuation values were modelled as a function which represents the loss L in dB as L - Kdn where d is the foliage depth in metres and k is a constant. The backscatter signal level emerging from such media into free space and its dependence on the azimuthal direction of the receiving antenna is also examined, and results are characterised in terms of the scattering cross section per unit area. The measured attenuation functions and backscatter signal level are compared with predictions obtained from a theoretical model based on the radiative energy transfer theory to estimate the values of the model parameters which characterise the vegetation medium.