Thermal Effects on a 4.2 m Center-Fed Cassegrain Antenna Strut in the Alphasat Ka- and Q-/V-Band Aldo Paraboni Propagation Measurements

Abstract

Large gateways of future satellite communications (Satcom) systems will likely operate at Q-/V-band frequencies (40-50 GHz) to take advantage of the larger available bandwidth. On the other hand, Q-/V-band Satcom systems suffer from highly variable propagation losses, which must be accurately assessed and modelled. The Alphasat Aldo Paraboni Propagation experiment, conceived and realized by the Italian Space Agency (ASI), has been running since 2014 to investigate carefully the propagation effects in the Ka and Q bands and, thus, to support the design of high throughput systems and propagation impairment mitigation techniques. In the framework of this experiment, ASI deployed two large ground terminals (Cassegrain antenna with 4.2 m diameter) in Tito Scalo (South of Italy) and Spino d'Adda (North of Italy). This contribution investigates the effect of antenna strut elongation on propagation measurements, which causes an additional reduction of 1-2 dB in the received signal during sunny days.

In Situ Antenna Pointing Angle Calibration for Q-Band Satellite Ground Station

“…The Q-band beacon signal transmitted by the Alphasat is a constant power continuous wave (CW) signal at 39.402 GHz [1], [3]. A low-cost dual-branch Q-band beacon receiver has been developed and installed in Aalborg University (with location Latitude 57.0120 o north, Longitude 9.9943 o east and The geometry of satellite-earth link is illustrated in Fig.…”

“…Communication satellites are only quasi geostationary, e.g. the Alphasat satellite [1], [3] exploited in our measurement campaign. The satellite is not stationary seen from the earth, but rather presents a daily movement trajectory that depends on the orbit inclination.…”

Low-Cost Ka-Band Satellite Receiver Data Preprocessing for Tropospheric Propagation Studies

“…We were interested in characterizing rain attenuation statistics. However, in addition to rain, the received beacon signal power level can also be affected by other phenomena: gases, clouds, scintillation [ 7 ], temperature fluctuations of the unit electronics, antenna strut thermal expansion [ 8 ], the accuracy of the satellite tracking [ 5 ], etc.…”

“…Moreover, looking into the work reported by others, in [ 8 ], the authors discussed that the level fluctuations they observed were due to antenna strut thermal expansion. Their setup ( m dish, ≈56.5 dBi gain, ≈ beamwidth) included a very large dish and a temperature-stable receiver.…”