Frequency Dependence of Attenuation Due to Vegetation for Satellite Services

This letter presents the results of vegetation loss measurements at 2.0, 3.5, 5.0, and 6.5 GHz for elevation angles ranging from 20?? to 90??. The excess attenuation due to vegetation was measured at four different wooded locations using a remote-controlled airship as a pseudo-satellite. Measurements taken in an open field were used as a reference. The results are given as additional attenuation averaged over the whole range of azimuth and elevation angles for circular polarization. Average results from all four locations vary from 9 dB at 2.0 GHz to 14.5 dB at 6.5 GHz. Linear frequency dependence of vegetation attenuation was observed, and a corresponding empirical model providing the additional vegetation loss as a function of the frequency was derived in closed form. The results are then compared to the literature.