PAGE CONTENTS
Objectives
The double objective of the activity has been, on one hand, to design two compact C-band antennas addressing single and multiple feed per beam configurations and, on the other hand, to manufacture and test an engineering model (EM) of a C-band feed assembly producing one beam.The EM feed assembly includes all elementary components to validate RF performances at feed level. A special effort has been put on size and weight reduction, selection of materials, optimization of processes involved and robustness with regards to PIM.
The work logic has been as follows: two Multibeam Mission scenarios have been selected and their multibeam antenna-reflectors geometries, includingSFB and MFB configurations, have been defined. From those antennas, the feed design requirements have been derived.
A trade-off between both configurations, based on RF performance and accommodation aspects has been done and eventually the MFB configuration has been selected for further investigations. On a second stage, the EM that consists of representative focal components to generate a single spot beam have been manufactured and tested.
Challenges
A trade-off between single-feed-per-beam (SFB) and multiple-feed-per-beam (MFB) reflector antenna configurations has been performed on continental and sub-continental coverage. Considering the large reflector apertures required for proper gain and beam-to-beam isolation, the MFB configuration has been preferred as only two reflector antenna are required to produce the full coverage in transmit and receive.
The feasibility of the novel approach has been demonstrated by the manufacturing and testing of an MFB feed array leading to extreme feed system height reduction when compared to an equivalent feed array in an SFB configuration. This height reduction is obtained thanks to the use of bar-line technology and to the use of a small and efficient radiating element. The model was tested successfully for PIM. The array losses are better than 0.5dB in worst case.
Plan
The first group of tasks has included a state-of-the-art analysis and definition of candidate missions based on identified needs (Milestone 1) and associated antenna and feed requirements (Milestone 2). Preliminary RF design analyses have been focused on the two most relevant feed assembly solutions further detailed at RF level. Based on these detailed RF designs, one solution out of the two has been selected to proceed with the next Tasks (Milestone 3).
The second group of tasks has been related to the feed assembly detailed designs: mechanical and thermal analyses, as well as updated RF analyses (Milestone 4) and this has led to the manufacturing of an EM. For the environmental testing, typical telecommunication GEO satellite mission requirements were considered (Milestone 5). Finally, testing and analysis of results at feed assembly level were performed (Milestone 6).
Current Status
Project has been completed. All above mentioned tasks have been fulfilled : mission scenario definition, system, antenna and feed requirements derived. In addition, an engineering model of a compact Cband feed assembly (one spot) to prove the concept has been designed, manufactured and successfully tested.
