Description
The future generation of communication satellites will use multi-beam antennas providing wide-band two-ways communication applications. Active discrete lens antennas generate a multibeam coverage adopting only a single Tx/Rx aperture or two separated apertures instead of the current solutions based on multi-reflector systems. Reduced volume and maximum EIRP flexibility over the service area are the main advantages of this antenna. The activity has been divided in two phases. Phase 1 included trade-off between several discrete lens architectures, selection of the overall antenna architecture and preliminary design of the demonstrator. Phase 2 concerned the detailed analysis and design of the Tx on-board antenna together with the manufacturing, integration and testing of a small Tx demonstrator with 28 active elements radiating both opposite circular polarizations.
During the activity a Tx active lens for a Ka-band Inmarsat-like multibeam application with 1.75° spot beams and with a DC power consumption of 4 kW has been designed. The system uses a four colour reuse scheme and is able to radiate 13 active beams, with an EIRP of 55 dBW, selected between 121 spot beams of the Earth global coverage.
The active lens has 218 active elements radiating both circular polarization by means of two GaN SSPAs. The front and the back array are aperiodic to simplify the RF chain inside the discrete lens. A thermal control system with 27 heat pipes and 4 loop heat pipes has been designed to dissipate the heat power dissipated by the SSPAs.
