Description
This activity investigated suitable multiple beam antenna configurations for C-band applications. A trade-off between single-feed-per-beam (SFB) and multiple-feed-per-beam (MFB) reflector antenna configurations was performed on continental and sub-continental coverage. Considering the large reflector apertures required for proper gain and beam-to-beam isolation, the MFB configuration was preferred as only two reflector antenna are required to produce the full coverage in transmit and receive. A novel feed array design for periodic MFB feed systems has been developed. This feed array uses 6 radiating elements per beam and each radiating element is shared with 6 surrounding arrays. The radiating elements are shared only in polarization leading to fully decoupled Beam Forming Networks (BFNs). Furthermore all BFNs can be constructed in a single layer without crossings. The proposed feed array is associated with four colour re-use scheme different from the standard hexagonal one. The use of this feed array and associated re-use scheme in combination with square-rim or super-elliptical reflectors provides some improvement on the Carrier over Interferers ratio (C/I) when compared to standard circular-rim reflectors.
The feasibility of the novel approach has been demonstrated by the manufacturing and testing an MFB feed array leading to extreme feed system height reduction when compared to a feed array in comparison respect to SFB approach. This is due to the use of bar-line technology and to the use of a small and efficient radiating element. The model has no issues in PIM. The array losses are better than 0.5dB in worse case.
