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Graphene has attracted tremendous scientific interest due to its exceptional electrical and mechanical properties. EU-funded researchers explored the use of graphene for a reconfigurable antenna operating at terahertz (THz) frequencies.
THz frequencies hold a large number of potential applications in the field of telecommunications, as well as imaging and sensing. But for all these applications THz antennas are a necessity. Within the EU-funded project RASTREO (Multi-reconfigurable antenna solutions based on reflectarray technology), researchers studied the properties of graphene with the aim of developing a THz reflectarray.
A reflectarray combines all the advantages of a parabolic reflector with the planar design of a phased array of antennas. Graphene is a mono atomic layer of carbon atoms arranged in a honeycomb structure, a semiconductor that allows the propagation of plasmonic modes at THz frequencies. Moreover, its conductivity can be efficiently controlled by an electric field.
RASTREO researchers demonstrated dynamic tuning at a frequency of 1.3 THz. The reflection coefficient of a square graphene patch as a function of both the patch size and the chemical potential was also computed. The maximum phase variation was obtained for a graphene patch of 10 μm, reaching about 300 degrees which is enough to produce a pencil beam.
The results obtained laid the groundwork for the design and analysis of a reflectarray. In the case of a conventional reflectarray, 489 gold elements with a cell size of about 100 μm would be needed. RASTREO researchers used more than 25 000 graphene elements. The experimental prototype was fabricated monolithically, due to which the high number of elements did not have any impact on the cost.
The graphene-based reflectarray has been designed to radiate a pencil beam with a loss varying between 0.5 dB and 6 dB between1.1 THz and 1.6 THz. The details of its design and the performance evaluation have been described in two articles published in peer-reviewed journals and presented at international conferences.
The RASTREO project has opened a very promising research line with exciting applications in indoor and satellite communications and has already attracted significant interest for future collaborations.