Programmable beam steering and quasi-continuous phase shift on a 2-bit terahertz coding metasurface with...

Area of Science:

• Electromagnetics and Metamaterials
• Terahertz Technology
• Wireless Communication Systems

Background:

• Terahertz (THz) reconfigurable intelligent surfaces (RIS) are crucial for advanced wireless communication and radar.
• Existing 1-bit coding metasurfaces have limitations in beam steering precision and quantization errors.
• Quasi-continuous phase modulation offers higher precision but faces challenges in electrical control and integration.

Purpose of the Study:

• To propose and demonstrate a 2-bit multimodal THz quasi-continuous phase shift coding metasurface.
• To enable real-time programmable phase shift control and 2-bit beam steering in the terahertz domain.
• To overcome the limitations of 1-bit coding metasurfaces and electrical switch performance.

Main Methods:

• Design of a meta-device using asymmetrically configured high electron mobility transistor (HEMT)-dipoles.
• Utilizing 2-dimensional electron gas (2DEG) density variations for local-field modulation and quasi-continuous phase shift (0° to 350°).
• Implementing Snell's law with optimal 2-bit coding states for array phase gradient construction and beam steering.

Main Results:

• Achieved a quasi-continuous phase shift from 0° to 350° at 0.376 THz with a minimum step of 6°.
• Demonstrated real-time beam steering from 21° to 48° within the 0.365-0.385 THz range.
• Experimental results closely align with simulation findings, confirming the device's performance.

Conclusions:

• This work presents the first electrically controlled 2-bit beam steering using a quasi-continuous phase shift metasurface in the terahertz domain.
• The proposed metasurface offers a practical solution for real-time phase modulation and programmable single-beam electronic steering.
• The technology holds significant promise for applications in THz wireless communication, radar detection, and computational imaging.