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StatusOngoing
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Status date2008-04-24
This study deals with linguistic beams over Europe. Envisaged mission is broadcast or/and Multimedia in Ku band. Antenna S/S will provide both low side lobes and cross polarisation level for allowing re-use of frequency resources. It will be achieved by means of very large multibeam / multifeed antennas (up to 3.8m).
The generation of low level of cross polarisation is realised with a short focal length thanks to a gridded sub-reflector which compensates the deviation of the linear E-field vector induced by the offset of the reflector geometry. The use of such a grid in a Cassegrain geometry allows to overlap orthogonal beam without any side lobe degradation.
Main objective of the study is to build and test as an EQM a partial focal array fully representative in terms of RF, mechanical and thermal performances to the selected baseline solution.
This hardware will include:
- A focal array (about 20 horns + passive BFN),
- A compensated gridded sub-reflector.
This project addresses a way to increase data rates in Ku and/or C-band by means of the antenna S/S (very large aperture, low cross-polarisation and side lobe levels for frequency re-use).
- Significant increase of today C & Ku band data rates.
- Multimedia mission in Ku-band. Large coverage for C-band.
- Alternative to Dual Gridded Reflector of large dimension.
10 beams over Europe are generated by means of 4 frequency slots in linear polarisation (H or V).
Frequency bands are 12.5-12.75 GHz for Tx and 14-14.25 GHz for Rx EIRP of TBCdBW per 36 MHz channel and G/T#12 dB/K are expected.
The study is divided into three parts:
- Part 1: selection of a mission and associated antenna S/S. Preliminary Design and analysis of the selected antenna. Definition of a representative hardware for manufacturing purpose.
- Part 2: Detailed analysis, Manufacturing and Test of the selected hardware.
- Part 3: Study of the concept in C-band.
Antenna S/S is composed of two Tx antennas in the lateral walls associated to polarisation grids for improving the XPD: the largest (located in the east panel, ?3.2x3.5m) is dedicated to the most demanding beams and the lowest (located in the west panel, ?2.8m) is dedicated for the less demanding beams. One Rx Dual Gridded Reflector located in the earth panel.
High saturated EIRP and G/T are provided on the whole coverage (63 dBW).
A partial hardware, fully representative of the overall complexity, has been manufactured: it consists in one beam of 21 feeds (horn + BFN) associated to a polarisation grid around 0.8mx1m:
- CDR analysis of both sub-reflector and feed array have been completed,
- A representative hardware (feed + grid) has been measured providing excellent level of performance, fully in line with predictions,
- Thermal cycling and acoustic tests have also been completed on the Sub-reflector (EQM like).
Activites have been led in parallel to check the interest of such a concept for a C-band telecommunication satellite. The antenna S/S has resulted unmatched to such kind of application thanks to size limitation at grid level.