Antenna Structures

Optimisation of reshaping surfaces

The Structures Section is active in developing new concepts and technologies, in particular active shaping of reflecting surfaces for RF and optical applications. In this context new optimisation techniques are being implemented for the coupled RF-mechanical optimisation of reflector shapes, considering optimal Directivity and XPD together with stresses and strains in the shell materials.
On-orbit reshaping of antenna reflectors offers the possibility of reconfiguring satellite antennas to adapt to market evolution by redefining coverages. The strategy of optimization of the shape of the reconfigurable reflector is a key aspect for proving the validity of the concept. The detailed mechanical response of the reflector needs to be taken into account when analysing the reshaping, in order to alleviate the stress states arising under the action of electro-mechanical actuators. The actual overall shape of the reflector must then be considered by the RF computation of the pattern resulting within the coverage on Earth. The shape optimization of the reflector has been implemented with the method of Simulated Annealing (a global optimisation technique as opposed to local ones) and taking the maximum principal stresses in the reflector as the cost function to be minimized.

The method shows reduction of the stress levels on the reflector to about 1/5 of those that would be obtained from a surface optimized in purely RF terms. It managed to escape the local optima most easily accessible from the starting point of the search, and it respected the required RF constraints of minimum Directivity and Cross-Polar Discrimination within a European coverage.
Minimization of the Maximum Principal Stress
Fig. 11. Minimization of the Maximum Principal Stress on reflector- with Simulated Annealing [R5].
Last update: 11 March 2013

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