Frequency Scaling from Ka Band to Q Band: Comparison of Two Approaches

To satisfy the need of higher data rate requirements, SatCom systems are gradually shifting to operate at higher frequencies. This increase in frequency can reduces the availability of Earth-satellite links because of the stronger effect that the troposphere has on the signal. Therefore, a simple static margin to cope with tropospheric impairments is no longer sufficient, and more sophisticated fade mitigation techniques must be adopted. One such technique is the uplink power control. Knowing the state of the link (i.e. the attenuation level) in real time at a particular frequency, which can be achieved via a beacon signal being transmitted by the satellite to the ground station, the attenuation level at the uplink frequency can be estimated using frequency scaling models. Consequently, the uplink transmission power can be modified to overcome the encountered attenuation. This research activity is carried out in the context of the Alphasat Aldo Paraboni propagation campaign. Data are collected from the Tito Scalo (40.60°N 15.7°E) and Spino D’Adda (45.4°N 9.5°E) ground stations, which receive unmodulated continuous wave beacon signals at 19.7 GHz and 39.4 GHz from the ALPHASAT geostationary satellite. Such data is used to investigate the accuracy of instantaneous frequency scaling approaches. In particular, two models are applied to estimate the attenuation at 39.4 GHz from the one at 19.7 GHz: the empirical model proposed by Drufuca and a more physically-based approach relying on the prediction of the specific rain attenuation at both frequencies from the concurrent rain rate information. The effectiveness of the two models is quantified by comparing the estimated attenuation at 39.4 GHz with the measured one. To this aim, data collected during two full years of experimental campaign (2015 and 2016) is used.