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Application of volumetric multiple scattering approximations to foliage media

Authors

  • Douglas Tamasanis


Abstract

Vegetation media may be viewed as two or more different types of dielectric scatterers arranged in a random geometric configuration in a surrounding “host” medium. This allows the vegetation to be treated as a continuous medium where the propagation of the waves through that medium is governed by an effective dielectric constant, (ε*). In this paper, several multiple scattering approximation techniques were used to quantitatively estimate the values of the effective dielectric constants for vegetation media based on the foliage density and dielectric properties of the scattering elements composing the vegetation. Because this formalism is not computationally intensive, it is useful for modeling the propagation losses experienced by an electromagnetic wave propagating through vegetation media in electromagnetic scattering or radar simulations. The theoretical approximations of ε* are compared with data at three levels. First, the calculated values of ε* were compared with values reported in the literature. Second, the effective dielectric constants for a foliage environment were used to calculate attenuation coefficients of coherent waves propagating through dense vegetation. The calculated attenuation constants were compared with experimental measurements reported by various authors at frequencies between 50 MHz and 3.2 GHz, resulting in good agreement. Finally, the values of ε* were incorporated into a bistatic scattering model which was used to calculate an effective normalized scattering cross section σ0 for a grass- and forest-covered terrain. This was compared with L band data resulting in excellent agreement between theory and experimental data.