Architecture for sub-100 ms Liquid Crystal Reconfigurable Intelligent Surface Based on Defected Delay Lines

Abstract

Reconfigurable Intelligent Surfaces (RISs), comprised of passive tunable elements, are emerging as an essential device for upcoming Millimeter Wave and Terahertz wireless systems. A fundamental aspect of the device involves the tuning technology used to achieve reconfigurability. Among alternatives such as semiconductors and MEMS, Liquid Crystal (LC) offers advantages such as cost- and power-effective large-panel scalability. In this context, conventional LC-RIS approaches face limitations in optimizing for bandwidth, response time and loss simultaneously, requiring trade-offs between them. In this work, we detail a new architecture for LC-RIS with compact defected delay lines that provide continuous, 360-degree tunability, enabling RISs with fast response time, wide bandwidth and low loss. A RIS with a thin 4.6 μm LC layer is designed, fabricated, and characterized, exhibiting response times of 72 milliseconds, insertion losses below 7 dB, and a 6 GHz (10.9%) bandwidth at 62 GHz, all while utilizing a lossy glass substrate and gold as a conductor.

Electronically Reconfigurable Reflectarray Antenna Based on Single-Layer Liquid Crystal With Independent Dual-Polarization Control

“…Moreover, among other advantages, LC allows a continuous (not discrete) tuning and its inherent power consumption is close to zero. Although the response time of LC in mm-wave devices is naturally larger than other technologies, different works have demonstrated several strategies to reduce such times down to the millisecond scale at mm-wave frequencies [5]- [8].…”

“…Numerous LC-based reflectarray unit cells have been introduced in the last decade, with the aim of improving the performance in terms of reconfiguration bandwidth [9], achievable phase shift [10], scan range [11], losses [12], [13] and temporal response [7], [8], [14]. While there exist several passive unit cells targeting different static polarization manipulations [15]- [17], a very limited number of reconfigurable [18] and LC-based reflectarrays with polarization-sensitive capabilities have been presented.…”