The system implications of 6/4 ghz satellite‐to‐ground signal depolarization results from the intelsat propagation measurement programme

Abstract

AbstractThe results of six experiments to measure 6/4 GHz signal depolarization are presented. The measurement sites varied from the tropics to 57°N latitude and elevation angles between 12° and 38° were employed. In two of the experiments, simultaneous measurements at 6 GHz and 4 GHz were made along the same path to measure the correlation between the depolarizations occurring at the two frequencies.It was found that, in all cases, rain was the dominant depolarizing mechanism. Where the occurrence of ice depolarization was significant the magnitude of the ice depolarization occurring was not system limiting on a statistical basis. The correlation between up‐link and down‐link depolarization occurring along the same path was found to be very good both on an instantaneous basis and a statistical basis. The use of open‐loop up‐link depolarization compensation mechanisms should therefore be feasible. An examination of the depolarization fluctuation spectra obtained in some severe depolarizing events during one of the experiments would indicate that the settling time for such a mechanism should be on the order of 1 s. The use of simple, ‘non‐perfect’, depolarization compensation mechanisms allied to a low‐cost, spectrally efficient FEC system may prove to be the best compromise in some locations that experience severe depolarization.