Philippe Voisin

From stentor to skybridge, different problems, one product line for active antennas☆

Abstract ALCATEL, has a long record of expertise in the field of active antennas, Stentor, French geostationary telecommunication technological programme, initiated in late 1995, offered the first opportunity to develop and qualify a flight model and experiment it in the sky. Now, Alcatel promotes Skybridge multimedia LEO constellation. This new commercial project relies heavily on active antennas for the spacecraft telecom payload. The Skybridge constellation will provide access to interactive multimedia high data rate services for private and professional users with a worldwide coverage. To offer the needed relay capacity, the payload includes a compound of multibeam transmit and receives fully adaptive antennas, to ensure smooth and permanent tracking of zones to be covered. The paper recalls briefly the telecom mission of Stentor active antenna payload, designed for multibeam broadcast service in Ku band, in permanent and beam-hopping modes and the requirements of Skybridge telecom payload, also in Ku band and illustrates how the two solutions have a common background. The Stentor active antenna (AATX) is a necessary step towards meeting the challenges of Skybridge payload, not only in terms of performance, mass and integration but also with the aim of reducing costs and securing the development plan of the project. A technical description of the two active antenna repeaters leads to review heritage and new challenges in the following areas: — radiating elements — active RF chain and filtering — beam-forming network — command and pointing — power conditioning — test facilities and methods