Compact Varactor-Integrated RIS for Wideband and Continuously Tunable Beamforming

TL;DR

This paper introduces a compact, wideband, and continuously tunable RIS with a low-profile design, capable of precise beamforming over a broad frequency range, suitable for advanced wireless systems.

Contribution

The paper proposes a novel RIS design with a middle patch layer that achieves wideband and continuous phase control without increasing thickness.

Findings

Achieves 310° phase shift over 10% bandwidth at 6.1 GHz

Demonstrates stable performance of a 10x10 RIS array

Enables precise beam control across 600 MHz bandwidth

Abstract

This letter presents a novel Reconfigurable Intelligent Surface (RIS) that features a low-profile structure, wide operating bandwidth, and continuous phase control. By incorporating a middle patch layer without introducing an additional air gap, the proposed design maintains a thin form factor, while achieving a smooth 310{\deg} phase shift over 10\% bandwidth at 6.1 GHz with excellent reflection. A fabricated 10*10 RIS array exhibits stable performance, enabling precise beam control across a 600 MHz bandwidth. These results highlight the potential of the proposed low-profile, wideband RIS with continuous phase tuning for next-generation wireless communication systems.