Attenuation statistics of non rainy atmosphere at 20-30 GHz

In the frequency bands above 20 GHz, in non-precipitating conditions, the atmospheric components relevant to radiowave propagation are oxygen, water vapour and the liquid droplets of clouds. Whilst cloud absorption increases with frequency, gases present absorption peaks, around 22 GHz and 60 GHz for water vapour and oxygen, respectively. These features have an impact on those satcom systems, such as commercial VSATs and business direct access terminals, where the power margin is reduced and the adoption of sophisticated countermeasures is limited by dimensions and cost effectiveness. The results are presented of the experimental campaign carried out with a dual-channel 20/30 GHz radiometer at Roma, Italy, along four years, September 1992-August 1996. Statistics are produced of zenith atmospheric attenuation in non-rainy conditions on a yearly basis, as well as for average seasons, months and hours of the day, from which the expected attenuation can be observed. Careful analysis is also focused on the two separate contributions of water vapour and cloud liquid.