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 degrees incidence. It is found that the main scatterers are the leafy branches, and the difference between sigma /sub vv/ and sigma /sub hh/ is significant at the upper portion of the tree. At the lower portion of the tree sigma /sup o//sub vv/ and sigma degrees /sub hh/ have almost the same level. For a group of trees the angular trends of sigma degrees /sub vv/ and sigma degrees /sub hh/ are measured. It is found that the levels of sigma degrees /sub vv/ and sigma degrees /sub 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. >