Ka-Band signal propagation experiment at NESAC Umiam

A Ka-Band signal propagation study under tropical monsoon climate was taken up jointly by ISRO/ONERA/CNES. The program was aimed at finding the degree to which Ka-Band signals get affected by Rain. Dual cross-polarized Ka Band beacon signals onboard GSAT-14 satellite, of frequencies 20.2 GHz and 30.5 GHz are used for the experiment. Data available by various instruments were compared with ITU-R predicted values. Results for the years 2016 and 2017 at Umiam shows underestimation of both Rainfall and Signal Attenuation by ITU-R predicted models. It has also been found that the Rainfall is mostly concentrated in three months (June, July, August) and the maximum attenuation that Ka-Band signals suffer during rain at Umiam  is around 30-40 dB. The actual Rainfall and Attenuation of both 20.2 GHz and 30.5 GHz signals have been compared with ITU-R predictions and has been found to be much above the predicted levels. A Study of the Z-R relationship for the rainfall and comparison with known relations indicate that a new distribution is required for the region.