Effect of tree structure on X-band microwave signature of conifers

Experimental studies are performed on some coniferous trees, Austrian pine, Nordmann spruce, and Norway spruce, to investigate the relation between the tree architecture and radar signal at X-band. For a single tree, the radar cross section (RCS) is measured as a function of the scatterer location at 90° incidence. It is found that the main scatterers are the leafy branches, and the difference between σ_vv and σ_hh is significant at the upper portion of the tree. At the lower portion of the tree σ^o_vv and σ°_hh have almost the same level. For a group of trees the angular trends of σ°_vv and σ°_hh are measured. It is found that the levels of σ°_vv and σ° _hh are of the same order, but their angular trends vary from one tree species to the other, depending on the tree species structure. The experimental results are interpreted with the help of a theoretical model which accounts for the structure of the tree