A varactor-based 1024-element RIS design for mm-waves

Abstract

This paper reports a reconfigurable intelligent surface (RIS) for beamforming and beam steering applications operating in the millimeter wave (mm-waves) frequency band. The proposed 2-bit RIS design is implemented using a radar cross-section (RCS) approach in ANSYS HFSS for performance evaluation and system-level analysis. It is based on split-ring resonator (SRR) unit cells, tuned by varactor diodes, comprising 1,024 elements arranged in a 32 × 32 matrix with linear gradient phase configuration operating at 24.5 GHz over the fifth generation of mobile communications New Radio (5G NR) frequency range 2 (FR2). A beam steering from −60° to 60° in the azimuth plane is demonstrated for mm-waves coverage extension. Numerical simulations of RCS patterns from −10° to −60° and from 10° to 60° with approximately 3 dB scan loss manifest the applicability of the proposed RIS towards the sixth generation of mobile communications (6G). Furthermore, simulated results of angular reciprocity prove the RIS response up to 110° under an oblique incident wave at 60°. To the best of our knowledge, this is the highest RIS angular reciprocity reported in the literature, validating its application to coverage extension from −60° to 60°. In addition, the RCS level and reflected angle relationship are modeled for system-level analysis purposes.

Rapid Prototyping of Anomalous Reflective Metasurfaces Using Spray-Coated Liquid Metal

“…Reconfigurable intelligent surfaces (RISs) promise to improve coverage for signals negatively impacted by obstructions present in the line-of-sight (LOS) path, making them an attractive technology for 5G and beyond mobile communications [1]. A typical RIS combines passive reflective elements with active devices such as varactors [2][3][4][5] or PIN diodes [6][7][8][9], while others use phase-tunable materials such as liquid crystals [10][11][12], 2D materials [13][14][15][16][17], or phase-change materials [18,19]. Creating a tunable reflection phase gradient across a surface enables the RIS to dynamically redirect an incoming signal to an anomalous direction not predicted by Snell's Law.…”