Simulating the Radar Cross Section of a Bare Tree: From Megahertz to Terahertz

An approach to estimate a radar cross section (RCS) of a tree through numerical simulations is studied. As an initial work, this paper covers bare trees with a trunk and branches and without leaves. Recent advancements in three-dimensional (3D) modeling of trees and electromagnetic solvers allow simulation of field scattering from a whole tree. There are however open issues in performing the simulations, i.e., 1) obtaining 3D models of tree trunks and branches, especially whether they have to be multi-layered or not; 2) knowing dielectric parameters of tree trunks and branches, especially for higher frequencies than 10 GHz; and finally, 3) using a right field solver depending on the electrical size of a tree. In response to the open issues, we propose suitable 3D models of tree trunks and branches, show our present knowledge of dielectric parameters of living trees, and finally demonstrate impacts of branches in addition to a trunk on the estimated RCS through numerical simulations at 1000 MHz to 0.1 THz.