Large Deployable Reflectors: Enhancing the Mesh Reflector RF Performances
Shaped surface reflector antennas are the preferred antenna type when a contoured beam illuminating a service region on the Earth from a communications satellite shall be achieved. The size of the reflector aperture (relative to the wavelength) determines the level of the minimum directivity on the service area and the directivity roll-off to areas using the same frequency and polarisation.
So far shaped surface reflector antennas have been usually manufactured with solid surfaces which ensures that the surface has the predicted shape. However, the aperture size is then limited by the available space and volume of the satellite configuration and launcher payload bay. A way to overcome this problem is to replace the solid reflector surface by a stowable and unfurlable mesh surface. Hence, the reflector in its stowed position during launch achieves a shaped (parabolic) reflecting surface once it is in its orbit. The challenges for this and some possible design solutions will be addressed in this paper both from an electrical as well as mechanical point of view for a shaping scenario of a large Cband reflector. Especially results achieved under the ESA project AMPER (Advanced Techniques for Mesh Reflector with Improved Radiation Pattern Performance) will be presented.
The investigation in RF performance carried out by TICRA covers the definition of several ranges of possible shaping with different shaping density. The mechanical and hardware implementation of the shaped surface is achieved by means of an equilibrium network carrying and properly tensioning the reflective metal mesh. Several LSS propriety analysis tools for proper form finding and optimization of the mesh type surfaces are used. This approach together with the iteration process between RF and mechanical analyses will be also presented.
In addition, different means of grating lobes reduction (GLR) of the large deployable mesh reflectors will be addressed via results achieved from RF investigations for finding the theoretical basis of a faceted surface arrangement. This will minimize the grating lobes to the acceptable levels.
Ongoing work is related to design and manufacturing of a shaped mesh reflector demonstrator of 2.3 m aperture diameter. The demonstrator will be tested in the planar near field scanner RF facility of ESA. Mechanical tests will also be carried out to support the applicability and verification of the prediction math models established.
Publication: 3rd International Conference on Advanced Lightweight Structures and Reflector Antennas
Place: Tbilisi, GeorgiaDownload PDF