HD-SAT modems for the satellite broadcasting in the 20 GHz frequency band

Abstract

We present two satellite modems developed in the frame work of the European RACE II HD-SAT project. We describe the HD-SAT system by presenting briefly the overall system. The propagation conditions in the 20 GHz range are particularly detailed as well as the technical answer: the graceful degradation concept. We deal with the variable bit rate-TCM 8PSK modem. The features of this modem, mainly the variable bit rate possibilities between 85 and 70 Mb/s, are described. We describe the "graceful degradation" modem which uses a hierarchical modulation scheme with time multiplexed modulation.