A Note on the Computed Radiation Patterns of Dipole Antennas in Dense Vegetation

摘要

A mathematical model of a short dipole antenna in a homogeneous, isotropic forest medium is developed. Height gain function and directivity patterns at hf are calculated for two cases, antenna in the open and in a forest, and these calculations are compared with some preliminary measured patterns and gain is obtained. Dipole gain at low elevation angles is found to increase in the forest (over the open-field case). Permutation of the six parameters of the model (permittivity and loss tangent of both earth and forest, antenna height, and forest height) indicates that the effect of antenna height is the most significant. Forest height and permittivity of the forest becomes important at the very low elevation angles and the loss tangent of the earth becomes important at low antenna heights. The dielectric constant of the ground and loss tangent of the forest are apparently relatively unimportant variables when checked over the ranges that seem reasonable for tropical forests. (Author)