Field trials of the VHF data exchange system (VDES) satellite downlink component

This paper focuses on analysing and characterising the communication channel of the VDES satellite downlink component by carrying out a measurement campaign of the VDE-SAT signal. The VHF downlink signal was transmitted from the Norwegian satellite NORSAT-2 operated by Space Norway. Three simultaneous carriers, specified in ITU-R M.2092-0, were transmitted in the test waveform: carrier 1 with BPSK/CDMA-8 modulation, carrier 2 with π/4 QPSK modulation and carrier 3 with 8PSK modulation. In addition, the satellite also transmits a CW carrier for test purposes. During this work a COTS-based receiver station has been designed, and installed on the roof of a house next to the sea. An embedded software application was implemented to automatically capture the test waveform every time the satellite was over the horizon. All the captured data was processed offline and the received waveform was thoroughly analysed, in order to assess the quality of the received signal and model the communications channel. The most relevant results derived from this work are presented in the paper.