Effects of Refractive Index Gradient Layers on Tropospheric Links

Abstract

The effects of refractive index gradient layers on the path-loss of troposcatter links have been investigated. The calculations are based on the Kanpur-Nainital troposcatter links. The path-loss is given in terms of the scatter angle which is determined by ray tracing. The ray trajectories are given for: (i) an assumed theoretical model of a gradient layer superimposed over an exponential troposphere and (ii) measured refractive index profiles over Kanpur-Nainital region. It is found that the effect of a negative gradient layer close to the transmitting antenna is to decrease the path-loss. On the other hand, positive gradient layers increase the path-loss. From the available refractivity data over the Kanpur-Nainital region it is found that the possibility exists for ducting over the Kanpur-Nainital link during winters. Path-loss during the dry summer months (Feb.-Apr.) is found to be higher than the predicted average path-loss for the link.