illustrates the
atmospheric attenuation up to 1 THz together with the dry air component, calculated for the standard ground-level
atmospheric conditions [12] and as per the Recommendation ITU-R P.676-9 [13]. Additionally included in the figure are
the attenuations due to rain for rain rates of 4, 16 and 50 mm/h, representing moderate, heavy and violent rain categories,
respectively. Recommendation ITU-R P.838-3 [14] provides the procedure to compute the specific attenuation due to rain for
frequencies up to 1 THz and horizontal polarization is assumed for calculations. According to the recommendation, the
general behaviour of rain attenuation between 1 and 1000 GHz is an increasing function with a declining rate which reaches
its maximum at around 100 GHz and then flatlines