AZIMUTHAL SCATTERING PATTERN OF TREES AT X-BAND

The azimuthal scattering characteristics of a variety of fully foliate d trees were measured in the field using a short-range X band bistatic radar system operating at 9 GHz. Azimuthal measurements were made for both VV and VH polarizations over a 180-degrees angle between the tra nsmitter and receiver ante at 10-degrees intervals. Data were collecte d at transmit and receive ranges of approximately 5 m, and the beam im pinged horizontally on the trees. The azimuthal power pattern, normali zed to the copolarized backscattered power, showed a peak in the forwa rd scattering direction (azimuth angle of 180-degrees) due to direct c oherent transmission, whose magnitude was seen to depend on the foliag e area density. The diffuse bistatically scattered power in the range of azimuth angles between 10-degrees and 90-degrees showed standard de viations of the order of 4 dB. In addition, needleleaf trees were foun d to depolarize the incident energy more than the broadleaf trees, wit h depolarization ratios of the order of -2.2 dB and -6.3 dB, respectiv ely, for bistatic scatter, and of the order of -4.5 dB and -8.9 dB, re spectively, for backscatter.