Wideband radar phenomenology of forest stands

In this paper, experimental ultra wideband radar backscatter response of a forest stand for remote sensing using applications are presented. The radar signal is a a zero-mean pulse with a duration of 1.5 ns, and rise time of 0.1 ns occupying a bandwidth 3 GHz from 0.5 GHz-3.5 GHz. The transmitter pulse amplitude exceeds 240 V in a 50 ohm transmission line giving rise to a peak power of about 1.15 kW. The transmit and receive antennas are broadband and with voltage standing-wave ratio of better than 1.2 up to 12.0 GHz. The radar is capable of transmitting both horizontal and vertical polarizations. Radar ranging of up to 180 m was achieved with a pulse repetition rate of 5 kHz. This radar was deployed to measure polarimetric backscatter from a 40-year old larch plantation stand with viewing angle varying from 50/spl deg/ to 75/spl deg/. For calibration, a corner reflector with 1 m side length was applied. Attenuation of the radar signal propagating through the canopy was extracted from the backscatter response of the the forest. Two specific features are observed from the attenuation data one having an exponential and the other having a power law dependence with distance. For the pulse scattered by the trihedral reflector imbedded in the forest, a phase diagram representing the parametric relation between the quadrature components of the receive signal is analyzed. The results obtained in this study show new possibilities for radar remote sensing of forest parameters with ultra wideband radars.