Voltage Supply for Liquid Crystal Reconfigurable Intelligent Surface Biasing
Dumitrache (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Arash Asadi – Mentor (TU Delft - Embedded Systems)
F.M.L. Portner – Mentor (TU Delft - Embedded Systems)
R Venkatesha Venkatesha Prasad – Graduation committee member (TU Delft - Networked Systems)
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Abstract
Liquid Crystal Reconfigurable Intelligent Surfaces (LC-RIS) are crucial for future millimeter-wave and terahertz wireless systems due to their ability to dynamically control electromagnetic waves. As LC-RIS requires very fast operation, an appropriate voltage supply with good response time must be developed to adjust each element independently. In this work, we present the design and implementation of a custom voltage supply tailored for LC-RIS applications. Our system integrates four daisy-chained LTC2688 digital-to-analog converters (DACs), providing 64 independently adjustable voltage outputs. We achieve a worst-case update time of 273 µs for all outputs, using a Raspberry Pi Pico as the SPI master with minimal C code. The voltage supply meets critical system demands, including the generation of 1 kHz square waveforms, a voltage range of ±10 V, and sub-millisecond response times, while maintaining ease of control through a programmable interface. We also developed a dedicated on-board power supply to meet the LTC2688’s multiple power rail requirements, enabling the entire system to operate from a single external input between 3.7V and 18 V. Furthermore, our design is scalable, allowing multiple boards to be daisy-chained for larger LC-RIS arrays. Our solution demonstrates a compact, fast, and scalable voltage control system suitable for high-performance LC-RIS platforms.