Microwave propagation constant for a vegetation canopy at X band

Authors

  • Ahad Tavakoli,

  • Kamal Sarabandi,

  • Fawwaz Ulaby


Abstract

An equivalent-medium model is developed for vegetation media to relate the propagation constant γ, associated with propagation of the mean field through a vegetation canopy, to the geometrical and dielectric parameters of the canopy constituents at high frequencies. The model is intended for media containing vertical dielectric cylinders, representing the stalks, and randomly oriented, arbitrary shaped thin dielectric disks, representing the leaves. The formulation accounts for absorption and scattering losses by both stalks and leaves. A resistive sheet model in conjunction with the physical optics approximation is used to model scattering by the canopy leaves, which is valid when the leaf dimensions are larger than a wavelength. The model is found to be in good agreement with experimental results at 10.2 GHz. The experimental component of the study included measurements of the attenuation loss for horizontally polarized and vertically polarized waves transmitted through a fully grown corn canopy. The measurements were made at incidence angles of 20°, 40°, 60°, and 90° relative to normal incidence. The proposed model is suitable for cornlike canopies, provided the leaves are larger than λ in size.

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