Nematic Liquid Crystals for mm-Wave Reconfigurable Intelligent Surfaces: a Hardware Perspective

Abstract: The surge of theoretical work investigating Reconfigurable Intelligent Surfaces (RISs) for wireless communication and sensing introduces an urgent need for hardware solutions enabling their implementation. A promising solution are RISs whose reconfigurability is achieved by nematic Liquid Crystals (LCs). In this colloquium, we will explore the basic physical principles and history of nematic LCs for microwave and mm-Wave frequencies. After an overview of several LC-based reconfigurable components, we will focus on planar phase shifters based on Liquid Crystal Display (LCD) technology. Compared to previous LC realizations, these phase shifters can simultaneously achieve high compactness, wide bandwidth, and fast response times, all with moderate insertion loss. Finally, examples of LC-RISs will be introduced, as well as perspectives on future developments. 

 Biography: Alejandro Jiménez-Sáez received the master’s degrees (Hons.) in telecommunications engineering from the Polytechnic University of Valencia, Spain, and in electrical engineering from the Technical University of Darmstadt, Germany, in 2017. In 2021, he received the Dr.-Ing. degree (with distinction) in electrical engineering from the TU Darmstadt and the Freunde der TU Darmstadt prize for the best dissertation in electrical engineering. He obtained the Athene Young Investigator award at TU Darmstadt and leads the Smart RF Systems based on Artificial and Functional Materials independent research group. His current research interests include chipless RFID, electromagnetic bandgap structures, liquid crystal, and reconfigurable intelligent surfaces.