AZIMUTHAL SCATTERING PATTERN OF TREES AT X-BAND

The azimuthal scattering characteristics of a variety of fully foliated 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 transmitter and receiver ante at 10-degrees intervals. Data were collected at transmit and receive ranges of approximately 5 m, and the beam impinged horizontally on the trees. The azimuthal power pattern, normalized to the copolarized backscattered power, showed a peak in the forward scattering direction (azimuth angle of 180-degrees) due to direct coherent transmission, whose magnitude was seen to depend on the foliage area density. The diffuse bistatically scattered power in the range of azimuth angles between 10-degrees and 90-degrees showed standard deviations of the order of 4 dB. In addition, needleleaf trees were found to depolarize the incident energy more than the broadleaf trees, with depolarization ratios of the order of -2.2 dB and -6.3 dB, respectively, for bistatic scatter, and of the order of -4.5 dB and -8.9 dB, respectively, for backscatter.