Twist-Tuned Strong Coupling in Sub-GHz Wire Metasurface Bilayers

TL;DR

This paper demonstrates a twist-angle controlled, reconfigurable sub-GHz wire metasurface with strong near-field coupling, enabling compact, programmable resonant surfaces with broad angular tunability.

Contribution

It introduces a twist-tuned, sub-GHz wire metasurface platform with strong coupling and broad angular tunability, extending reconfigurable metasurfaces into VHF/UHF frequencies.

Findings

Achieved 2:1 frequency tuning from 409 MHz to 210 MHz.

Normalized coupling up to g = 0.43 with high cooperativity.

Confirmed near-field origin of the twist-driven hybridization.

Abstract

Twist-angle control offers a bias-free route to reconfigurable metasurfaces, yet its extension to deeply subwavelength resonant platforms at VHF/UHF remains limited. We demonstrate a sub-GHz double-layer wire metasurface formed by two identical wire grids separated by a gap G, with in-plane rotation angle as the sole tuning parameter. One-port, loop-coupled S11 measurements supported by full-wave simulations reveal twist-driven hybridization of the dominant resonant manifold. For small G, the lower hybrid resonance redshifts continuously from 409 MHz to 210 MHz (2:1 tuning), enabling compact, twist-programmable resonant surfaces. Simulations further show that twisting imprints moire-like magnetic near-field super-modulations. From resonance frequencies, linewidths, and normal-mode splitting extracted from the complex response, we obtain normalized coupling up to g = 0.43 with cooperativity exceeding unity over broad angular ranges, meeting the resolved-splitting criterion. The rapid collapse of tunability at larger G confirms the near-field origin of the interaction.