Tropospheric scintillation and attenuation on satellite-to-Earth links at Ka and Q band: modeling, validation and experimental applications

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

Realizzazione di una stazione terrena ricevente satellitare per studi di propagazione elettromagnetica in atmosfera

Il satellite per telecomunicazioni Alphasat, il più grande realizzato in Europa e collocato in orbita geostazionaria nel luglio del 2013, ospita a bordo una piattaforma scientifica (TDP-5 “Aldo Paraboni”) destinata allo studio della ropagazione elettromagnetica in atmosfera in alcune bande di frequenze a microonde tra cui la banda Ka (20 GHz) e la banda Q (40 GHz). Alle sperimentazioni partecipano numerose Università ed Enti di ricerca di tutta Europa, in Italia su iniziativa dell'ASI (Agenzia Spaziale Italiana) sono coinvolti, tra gli altri, il Politecnico di Milano e le Università di Roma Tor Vergata e Sapienza. Presso l'ISCTI (Istituto Superiore delle Comunicazioni e delle Tecnologie dell'Informazione) è stata realizzata una stazione ricevente con minima spesa, grazie all'utilizzo di componenti appartenenti a ricevitori non più operativi, e dotata di piattaforme open-source per l’implementazione di funzioni aggiuntiv

Analisi delle scintillazioni in aria chiara del collegamento alphasat in banda Q di Spino d’Adda tramite utilizzo di radiosondaggi

Le scintillazioni si manifestano come una variazione aleatoria indesiderata del segnale ricevuto. In questo articolo verrà data una prima analisi dei dati acquisiti dalla stazione ricevente del satellite Alphasat in banda Q di Spino d’Adda. Verrà inoltre effettuato uno studio di correlazione tra i dati meteorologici misurati a terra e il valore di scintillazione misurato tramite il ricevitore in banda Q. Dati relativi ai radiosondaggi della stazione di Milano Linate sono stati acquisiti per l’intero anno 2015 e sono stati usati per calcolare la costante di struttura dell’indice di rifrazione. Tramite il modello Rytov è stato stimato il valore relativo di scintillazione lungo la tratta interessata dal collegamento. I risultati così ottenuti tramite modellistica sono stati confrontati con le misure dirette di scintillazione, effettuate tramite il ricevitore a terra, focalizzando la correlazione in aria chiara tra dati simulati e misurati.Scintillations affect the propagated signal with an unwanted aleatory oscillation at the receiver. A first analysis of data acquired from Alphasat Q-band receiver station, located in Spino d'Adda (Italy), is performed. Correlation between meteorological measurements at the ground and measured scintillation from the Q-band beacon receiver (i.e., fluctuation of the received electromagnetic field) is investigated. Radiosounding data from north Italy station of 'Milano Linate' have been collected for the entire year 2015 and used to calculate the refractive index structure constant. Subsequently the amplitude scintillation variance is derived through the use of the Rytov model on the slant path. Results obtained using the scintillation model are compared with measured data from Alphasat beacon receiver, investigating the statistical correlation in clear air condition between simulated and measured data

Clear-air scintillation analysis of Q-band alphasat link at Spino d'Adda using radiosounding data

Scintillations affect the propagated signal with an unwanted aleatory oscillation at the receiver. A first analysis of data acquired from Alphasat Q-band receiver station, located in Spino d'Adda (Italy), is performed. Correlation between meteorological measurements at the ground and measured scintillation from the Q-band beacon receiver (i.e., fluctuation of the received electromagnetic field) is investigated. Radiosounding data from north Italy station of "Milano Linate" have been collected for the entire year 2015 and used to calculate the refractive index structure constant. Subsequently the amplitude scintillation variance is derived through the use of the Rytov model on the slant path. Results obtained using the scintillation model are compared with measured data from Alphasat beacon receiver, investigating the statistical correlation in clear air condition between simulated and measured data

AlphaSat Ka-band and Q-band receiving station in Rome. Development, status and measurements

A Ka-band (20 GHz) and Q-band (40 GHz) receiving station, located in Rome (Italy), has been designed and implemented to receive the beacon of the AlphaSat satellite Technology Demonstrator Payload 5 'Aldo Paraboni'. Ka-band station is complete and its preliminary measurements are shown. Mechanical antenna tracking is also foreseen. Q-band station is being assembled and should be tested in early 2015. A laboratory characterization of all blocks and subsystems has been carried out and is briefly described. The design and implementation of a W-band microwave radiometer is also on going, whereas Ka- and Q-band beacon data are combined with measurements from a meteorological station, raingauge and disdrometer