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 multilayered 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.

In this paper, we present the results of wave scatterer localization at 4.65 and 14.25 GHz in an outdoor-toindoor scenario at a traditional office building in Finland. The localization is based on a single-bounce model of interaction with a scatterer to localize the sources of measured multipath components. The estimated scatterer locations were mapped to an aerial photograph of the site and classified according to their location. We found that approximately two thirds of paths originate from higher order interactions with the environment. In contrast, one third of paths can be attributed to single-bounce interactions, with interior walls of the building being twice as strong sources of single-bounces as walls outside both in terms of power and number of paths.

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