Modular terahertz reconfigurable intelligent surface for dynamic electromagnetic wavefront control

This technology is a modular, chip-based reconfigurable intelligent surface that uses CMOS circuits to dynamically control terahertz waves’ amplitude and phase at gigahertz speeds, enabling advanced beamforming, holography, and high-speed wireless communications with low power consumption.

Background

The terahertz (THz) spectrum is a critical frontier for next-generation technology, offering the substantial bandwidth essential for ultra-high-speed applications like 6G wireless communications, advanced sensing, and high-resolution imaging. To effectively harness this spectrum, there is a pressing need for dynamic electromagnetic wavefront control at subwavelength scales. Systems capable of manipulating THz waves are required to enable sophisticated functionalities such as real-time beamforming, spatial light modulation, and holographic projections. These capabilities are vital for creating adaptive wireless links that can track moving receivers and overcome environmental signal blockages.

Despite this demand, current approaches for THz wavefront manipulation suffer from severe limitations. Traditional metasurfaces are static once fabricated, preventing real-time adaptation. While reconfigurable alternatives utilize phase-change materials, micro-electromechanical systems (MEMS), or tunable substrates, these methods are fundamentally constrained. They notoriously exhibit slow response times ranging from milliseconds to seconds, which is inadequate for high-speed communication. Furthermore, these platforms often demand high power consumption or impractical cryogenic cooling. They frequently rely on collective rather than individual element control, restricting complex wavefront engineering. Finally, conventional designs demonstrate poor scalability to large arrays and struggle with degraded impedance ratios caused by parasitic capacitances, preventing practical deployment.

Technology

This reconfigurable intelligent surface (RIS) technology operates at 0.3 terahertz (THz) frequencies using modularly tiled silicon CMOS chips. Each chip integrates a 12×12 array of individually addressable meta-elements featuring C-shaped split-ring resonators and eight NMOS transistor switches. Driven by on-chip shift registers, the system utilizes 8-bit digital programming to deliver simultaneous amplitude modulation up to 25 dB and phase shifts up to 260°. The modular architecture enables seamless scaling into larger arrays while maintaining low static power consumption. Additionally, the platform supports gigahertz-speed reconfiguration up to 5 GHz for dynamic beamforming, spatial light modulation, and holographic projections.

This solution is highly differentiated by an electromagnetic-circuit co-design that overcomes fundamental high-frequency transistor limitations. While traditional dynamic metasurfaces struggle with slow response times and collective element control, this technology utilizes subwavelength inductive loops that resonate with the switches’ parasitic capacitances. This local resonance boosts the effective OFF/ON impedance ratio by 12.5 times, enabling dynamic switching well beyond the transistors’ intrinsic cutoff frequency. Consequently, it achieves unprecedented gigahertz-speed, individual subwavelength element control. By leveraging standard 65 nm CMOS fabrication, the platform provides a scalable, low-cost, and highly efficient alternative to existing phase-change or MEMS-based approaches.

Benefits

  • Ultra-Fast Reconfiguration: Achieves gigahertz-speed switching (up to 5-10 GHz) for real-time dynamic wavefront control, vastly outperforming traditional metasurfaces that suffer from millisecond to second response times.
  • High Scalability and Cost-Effectiveness: Utilizes a modular chip-tiling architecture and standard 65 nm CMOS fabrication, enabling the low-cost, high-yield construction of large-area metasurfaces.
  • Precise, Independent Element Control: Provides 8-bit digital programming resolution for each individual meta-element, allowing for highly accurate, simultaneous control of both amplitude and phase.
  • Terahertz Frequency Operation: Employs an innovative electromagnetic-circuit co-design with resonant enhancement to operate effectively at 0.3 THz, successfully overcoming the intrinsic cutoff frequency limitations of standard transistors.
  • Exceptional Energy Efficiency: Operates with ultra-low static power consumption (approximately 240 µW per chip), making the technology highly suitable for battery-powered and energy-conscious applications.
  • Multifunctional Versatility: Serves as a unified platform capable of supporting diverse, complex applications including dynamic beamforming, high-speed spatial light modulation, and programmable holographic projections.
  • Seamless System Integration: The CMOS-compatible design allows for easy integration with other electronic components, such as THz sources and detectors, to create compact, fully integrated transceiver systems on a single silicon substrate.

Applications

  • 6G wireless communication networks
  • Autonomous vehicle THz radar systems
  • Lensless THz computational imaging
  • Adaptive beam steering for UAVs
  • Programmable THz holographic displays

Additional info

This scalable 0.3 THz reconfigurable surface employs modular 65nm CMOS tiling. Each meta-element integrates C-shaped split-ring resonators with eight NMOS switches. Subwavelength inductive loops resonate with parasitic capacitances, enhancing OFF/ON impedance ratios beyond intrinsic transistor cutoff frequencies. On-chip 8-bit digital registers enable 5 GHz reconfiguration speeds, facilitating dynamic beamforming, spatial light modulation, and holography through simultaneous amplitude and phase control with microwatt-scale static power consumption.