Design of liquid-metal reconfigurable reflectarrays with supporting computational tools

Abstract

Fifth-generation (5G) and beyond wireless networks use high-band frequencies to offer ultra-fast data rates with minimal latency. However, operating in these high-band regimes introduces significant challenges such as increased path loss and reduced signal penetration. Reconfigurable reflectarrays (RAs) present a cost-effective and efficient solution, capable of dynamically steering electromagnetic beams using phase-tunable unit cells. Traditionally, RA designs have relied on solid-state devices like PIN diodes, MEMS switches, or tunable materials for phase tuning. These approaches, though effective, are often hampered by fabrication complexity, considerable power consumption, and limited scalability. This thesis introduces a reconfigurable reflectarray that leverages the unique fluidic properties of the liquid metal Galinstan, enabling mechanical phase tuning without the drawbacks associated with solid-state devices, such as increased power consumption and limited scalability. This represents a substantial step forward in RA technology, as Galinstan’s deformability allows for innovative unit cell designs that can be reshaped and actuated via microfluidic techniques like continuous electrowetting (CEW) and electrocapillary actuation (ECA). These novel methods facilitate precise and low-power reconfiguration of reflectarray elements, setting this work apart from previous research. Several unit cell designs were modeled using Ansys HFSS, fabricated via soft lithography and laser micromachining, and tested in custom 3.5-GHz and 28-GHz antenna testbeds. Measured results demonstrate an ability to perform anomalous beam steering within an accuracy of 2 degrees for all fabricated prototypes, highlighting the precision and effectiveness of the proposed approach. In addition to these hardware innovations, this work developed a suite of computational tools that significantly streamline the reflectarray design workflow. These tools automate phase distribution calculations, optimize radiation patterns, and enable rapid prototyping of unit cell geometries, thereby reducing development time and minimizing human error throughout the design process. The presented liquid-metal RA paradigm offers a scalable, low-power alternative to conventional RA technologies and is particularly well-suited for dynamic wireless environments in which virtual line-of-sight links (VLoS) need to be reestablished.