Experimental Assessment of Cloud Attenuation in a Q-Band Slant-Path Link

Abstract

The use of millimeter wave Q/V bands in satellite communications is expected to grow in the near future. At these frequency bands rain is the main contribution to atmospheric losses, although the effect of clouds is also relevant. Propagation models dealing with attenuation produced by clouds are not widely validated by experimental data, because of the difficulty of isolating cloud attenuation from other propagation effects. This paper presents a novel method used to derive cloud attenuation in the absence of rain from Q-band excess attenuation measurements collected at Universidad Politécnica de Madrid, taking advantage of ancillary data from two co-located instruments: a disdrometer and a Ka-band beacon receiver. Using this procedure, time series of Q-band cloud attenuation have been extracted for a period of 5 years and the calculated statistical results have been compared to estimations derived from different models. Cloud attenuation statistics derived from measurements with this novel procedure are in good agreement with radiosounding-based models, whereas Rec. ITU-R P.840 model overestimate them. The use of the ERA5 TCLW (Total Column Cloud Liquid Water) time series are considered as suitable input data for cloud attenuation estimation, with results similar to those obtained from radiosounding observations.