DIGITALLY IMPLEMENTED MODEMS AND THEIR EFFECT ON FUTURE SATELLITE-COMMUNICATIONS SYSTEMS

Modems intended for high-speed satellite services have traditionally been based on analogue technology. It is only recently that the speed and density of digital hardware has increased to such an extent that economical digital modem implementations have become possible. This type of modem will allow the use of operational techniques which, up to now, have not been practical. In particular, digital implementations have the ability to rapidly change their data rate and modulation type. The basic principles behind two recent digital modem implementations are described and possible applications for this new technology are discussed.