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Reflectarray antennas: A promising alternative to reflectors and arrays

Published by Rob on Thu Jun 28, 2007 5:06 pm
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Reflectarray antennas – which mimic the performance of parabolic or other shaped reflector antennas using flat surfaces which incorporate phase correctors in their reflecting planes – are showing great promise for space applications.

Future satellite-based communications and remote sensing missions will require large antenna apertures, ranging from a few metres to 20 or even 30 metres. For these large apertures, accurate parabolic or other desired shapes are difficult to achieve and stowage and deployment can be difficult. Even for smaller antennas, accommodation of several curved reflectors on the same platform can be problematic.
Reflectarrays, based on flat reflecting surfaces, are an exciting alternative to traditional parabolic or shaped reflectors. The focusing or beam forming properties of a parabolic or shaped reflector are obtained by incorporating fixed or adjustable path/phase corrections in the flat surface. Typically, reflectarrays are obtained by printing metallic patches on one (or more) dielectric layers above a ground plane. The required reflection phase shifts are achieved by locally adjusting the patch dimensions. Beam reconfigurability or steering can be achieved by incorporating adjustable path/phase shifters in each element.

In 2004, with ESA Technology Research Programme (TRP) funding, a prototype of a three-layer printed reflectarray for dual polarisation with a different coverage in each polarisation was designed, manufactured and tested. The institutions and companies involved in the contract were: Polytechnic University of Madrid (Universidad Politécnica de Madrid, Spain); Institute for Lightweight Structures – Technical University of Munich (Lehrstuhl für Leichtbau [LLB], Technische Universität München, Germany); KRP-Mechatec Engineering, (Germany); Alcatel Alenia Space (France).

Telecommunications application

The reflectarray antenna prototype achieved a 10% bandwidth and has been introduced to replace a dual gridded reflector in a telecommunications mission with the following requirements: a contoured beam for European coverage in H-polarisation (11.45-12.75 GHz) and a pencil beam to illuminate the East Coast of the USA in V-polarisation (11.45-11.7GHz). The novelty of this work is the demonstration that two independent beams, one for each polarisation, can be generated with a single flat reflectarray surface, and consequently, a significant reduction in mass and volume can be achieved as compared with a conventional dual gridded reflector. The reflectarray concept appears to be promising not only for telecommunications applications but also to obtain new synthetic-aperture radar antennas for Earth observation missions.

As a continuation of the initial TRP activity, two parallel ARTES 5 contracts are now running, developing new reflectarray concepts using space qualified antenna technologies and offering coverage reconfigurability on ground before launch or during flight (from among pre-selected patterns). Full in-flight reconfigurability, possibly using MEMS, is expected to be developed and funded during the next TRP cycle.

Please feel free to discuss this topic further in the forums…

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