Effects of water-vapor on the Ka/Q band Earth-space radio propagation channel

Abstract: A higher frequency radio channel both increase the possible data rate and de- crease the required antenna size to efficiently transmit data. Higher frequency also introduce larger weakness to signal loss due to atmospheric effects. Al- phasat satellite conduct experiments for future use of higher frequencies by the Aldo Paraboni Payload. Budapest University of Technology have receiv- ing antennas for both transmitted Alphasat signals in the Ka band and Q band. Meteorological surface data is also gathered in close proximity of the receiving antennas. The relationship between the meteorological data and attenuation on the received signal is studied. A focus lies on the effects of water vapor and clouds.  International Telecommunication Union prediction methods for clouds and atmospheric gases are applied on the meteorological data. This provide a foundation for the analysis of received attenuation on the Q band signal at frequency 39,402 GHz. The analysis aim to investigate if there is any rela- tionship between surface meteorological data and atmospheric effects such as cloud and atmospheric gases. Cross-correlation was used to find similarities between the parameters.  The analysed data is over the month of April 2018. During this month seven different rain events were indicated by the rain rate tipping bucket. These regions showed strong influence of rain on the surface temperature and hu- midity was used to identify other regions with no rain characteristics. Only four out of 16 regions above 2,5 dB had no characteristics similar to rain with four other regions showing indistinguishable source. These eight regions were most promising of being caused by cloud and atmospheric gases. The large quantity of attenuation events below 2,5 dB made further manual analysis difficult. ITU methods predicted a maximum attenuation of 3 dB for clouds and atmospheric gases. Future work could improve analysis on attenuation events below 2,5 dB by pattern recognition with the characteristics found in this work.