mm-wave Reconfigurable Intelligent Surfaces based on Liquid Crystals.

Ponente: D. Robert Guirado.

Organismo: Grupo de Electromagnetismo Aplicado (GEA). ETSIT-UPM.

Fecha: 2 de Diciembre 2022.

Hora:  10.00 hora.

Lugar: Sala B-223, ETSIT-UPM.


Liquid Crystal (LC) technologies are starting to be studied at mm-wave bands in order to develop tunable devices that work properly at those frequency ranges. Because of its birefringence, by applying a low-frequency electric field to a cavity containing nematic LC, its electromagnetic properties can be varied and therefore the device response changes. This varying behavior is related to a continuous change on the electric permittivity, which can be leveraged to vary the resonant frequency or beam of an antenna, or to tune the different elements in a reflectarray antenna, to name a few. Recently, the use of nematic LC as the key phase-shifting element of the upcoming Reconfigurable Intelligent Surfaces (RIS), planar devices able to manipulate electromagnetic propagation, has been proposed, as it is one of the few tunable technologies with moderate cost capable of keeping the pace of the high frequencies (>100GHz) expected in future network generations beyond 5G. Nevertheless, the relatively slow switching times between states, in the order of seconds, is the main weakness of such LC-based devices. However, to be fully implantable in future ultra-reliable low-latency communication networks, improving these times is of utmost importance due to the stringent dynamic requirements of upcoming communication protocols. In this talk, different solutions to overcome this challenge will be discussed.