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A proof of concept demonstrator model of the lens, including 18 innovative passive radiating elements, has been designed, manufactured and tested.
The active lens antenna guarantees maximum flexibility in terms of RF power distribution over the service area according to the changes of traffic distribution during the satellite operative timeframe.
Volume and mass of the lens are reduced thanks to the introduction of Gregorian arrangement of two confocal paraboloids magnifying the small active lens. As the failure of a lens SSPA introduces only a graceful degradation of electrical performance, the active discrete lens does not require amplifier redundancies.
Differently from a phased array solution, its complexity increases in a little appreciable manner when increasing the number of coverage spot beams.
A Tx/Rx discrete lens is composed by two arrays both with N radiating elements. One array (front array) faces the free space and the other (back array) faces the primary feeds placed on the focal region. The elements of the front array are connected with the corresponding elements of the back array via transmission lines and SSPAs as shown in the following picture. The discrete lens feds a Gregorian arrangement of two confocal paraboloids which magnifying the image of the lens.
During the activity a Tx/Rx active lens integrated with a two confocal paraboloids for a Ku-band KaSat-like multibeam application with 0.85° spot beams and based on a secondary payload with a DC power consumption of only 6.0 kW has been designed. The system uses a four colour reuse scheme and is able to radiate 30 active beams, with an EIRP of 61 dBW.
The active lens is made of 593 active square elements each one radiating linear polarization in Tx/Rx band and equipped with two GaN SSPAs in the Tx path and two LNAs in the Rx path. Both the front and the back array are designed in according the McGrath configuration and they are periodic to obtain the maximum performance in terms of gain and beam scanning. A thermal control system with only 26 heat pipes and 4 loop heat pipes has been designed to dissipate the heat power dissipated by the active components. A supporting structure with high modulus carbon fibers was designed to limit the antenna mass budget.
The activity has been divided in two contractual phases. Phase 1 included trade-off between several discrete lens and reflector architectures, selection of the overall antenna system architecture and preliminary design of the demonstrator. Phase 2 concerned the detailed analysis and design of the Tx/Rx on-board antenna together with the manufacturing, integration and testing of the demonstrator shown in the following picture.
The development phase of the active discrete lens for multibeam applications can be classified now with a Technology Readiness Level (TRL) of 4.