MICROWAVE PROPAGATION CONSTANT FOR A VEGETATION CANOPY AT X-BAND

An equivalent-medium model is developed for vegetation media to relate the propagation constant gamma, associated with propagation of the me an field through a vegetation canopy, to the geometrical and dielectri c parameters of the canopy constituents at high frequencies. The model is intended for media containing vertical dielectric cylinders, repre senting the stalks, and randomly oriented, arbitrary shaped thin diele ctric disks, representing the leaves. The formulation accounts for abs orption and scattering losses by both stalks and leaves. A resistive s heet model in conjunction with the physical optics approximation is us ed to model scattering by the canopy leaves, which is valid when the l eaf dimensions are larger than a wavelength. The model is found to be in good agreement with experimental results at 10.2 GHz. The experimen tal component of the study included measurements of the attenuation lo ss for horizontally polarized and vertically polarized waves transmitt ed through a fully grown corn canopy. The measurements were made at in cidence angles of 20-degrees, 40-degrees, 60-degrees, and 90-degrees r elative to normal incidence. The proposed model is suitable for cornli ke canopies, provided the leaves are larger than lambda in size.