Modeling techniques for curved and tapered branches at different microwave frequencies

The effects of modeling the curvature and tapering of branches for various microwave frequencies are examined. The forest models that are currently being used represent branches as perfect dielectric cylinders. However actual branches are composed of segments decreasing in diameter along the branch length. Adjacent branch segments also have slightly different angles causing branch curvature. In this study, each branch is represented as a collection of cylindrical segments whose sizes and positions are known. The data for the calculations are obtained from actual branch measurements of red pine and jack pine trees using the “tree vectorization” technique which has been developed at the Canada Centre for Remote Sensing. For a given frequency and incidence angle, a curved and tapered branch can be approximated by an equivalent cylindrical branch. The equivalent cylinder can be determined by choosing the size and orientation so that the radiation patterns match closely. For curved branches, the radiation pattern at typical incident angles is calculated by adding the contributions from each branch segment coherently. It is observed that at low frequencies, the parts of the branch with thinner segments do not contribute to scattering. Therefore, the resulting equivalent cylinder is represented by the thicker part of the branch which is closer to the trunk