Link budget is a crucial step during the design of every communication system. For this reason it is fundamental to identify and estimate the effects of the atmosphere on the electromagnetic signal along the path from the source to the sink. Troposphere represent the bigger source of attenuation and scintillation for signals in the microwave and upper frequency spectrum. During last years we have participated in the European Space Agency “AlphaSat Aldo Paraboni” experimental campaigns to acquire up to date propagation data at two frequencies of interest for future communication systems. We realized two high performance low-noise receiver located in Rome, one at Ka and one at Q band (19.701 and 39.402 GHz) to detect the two signal beacons sent from the AlphaSat geostationary satellite to a wide area over Europe. Collected data from Rome receiving station have been analysed to measure excess attenuation and scintillation along the path. Such statistics collected in a database together with data from other experimenter will be in the near future a useful instrument, giving professionals updated data for their custom application design. Classical link budget techniques rely on climatological atmospheric statistics based on different time-scales, usually data collected for several years. In the background of the European Space Agency “STEAM” project, we proposed the use of high resolution 3D weather forecast models (up to 166m pixel resolution) for the calculation of excess attenuation and tropospheric scintillation for satellite to earth link. As a result, the estimation of these electromagnetic parameters to use in link budgets could be given no more as a statistical analysis of past events as in the case of Internation Telecommunication Union recommendation but as time-series forecast specific for the selected receiving station and along the slant path of the transmitted signal. Case studies for the use of this technique have been deeply analysed and results compared with data from the AlphaSat measurement campaign for the Rome and Spino d’Adda receiving station, confirming the validity even in different geographical regions. In everyday situations, propagation models based on statistics are often replaced by the use of easier to apply parametric models. Those have the advantage of the simplicity and the need of less input parameter to be applied. In particular, for what concerning the tropospheric scintillation, the Hufnagel-Valley refractive index structure constant (C2n ) parametric model is actually the most used, due to the simplicity and the relative accuracy. We here propose a new Cn2 polynomial parametric model (CPP) based just on the altitude z and a function C2 n0(to,RH0) that allow to calculate the ground refractive index structure constant just using the ground temperature (T0) and the relative humidity (RH0). In this work CPP and Hufnagel-Valley models are applied to different location around the globe to prove their accuracy. The obtained model could be also used in the future to realize a simulator able to generate random C2n vertical profiles specific for the receiver site.
Tropospheric scintillation and attenuation on satellite-to-Earth links at Ka and Q band: modeling, validation and experimental applications / MARZIANI, AUGUSTO MARIA. - (2020 Feb 18).
|Titolo:||Tropospheric scintillation and attenuation on satellite-to-Earth links at Ka and Q band: modeling, validation and experimental applications|
|Data di discussione:||18-feb-2020|
|Appartiene alla tipologia:||07a Tesi di Dottorato|