We’ve come a long way since the first generation (1G) wireless communication networks were launched in the 1980s. Initially catering to analogue voice communications, these early networks suffered from poor quality and limited coverage.
We’re now on the brink of launching 6G networks by 2030, which promise advancements including smart cities, 3D immersive augmented reality, high-fidelity mobile holograms and more.
The terahertz (THz) section of the electromagnetic spectrum is targeted for 6G communications due to its capacity to support extraordinarily high data speeds, capable of transferring terabytes of data in mere seconds. However, these higher frequency waves do not travel as far as lower frequency waves, potentially creating coverage gaps known as ‘blind spots’.
Prakash Pitchappa, a Research Scientist at A*STAR’s Institute of Microelectronics (IME), has been working on addressing these limitations. “In our research, we’ve developed a terahertz device based on a metasurface concept that can redirect transmitted beams in any chosen direction, controlled by the coding sequence of the metasurface,” Pitchappa explained.
A schematic illustration of a reconfigurable vanadium dioxide (VO2)-based metasurface which allows wide-angle THz beam steering. Based on different phase-modulated coding sequences (top left), a transmitted linear polarised wave (Ey) propagating along the z-axis can be steered as cross-polarised waves (Ex) to different angles. The enlarged unit cell schematic (top right) shows an eight-gap split ring resonator (SRR) embedded with VO2 in metallic (red) and insulating (blue) states, allowing for dynamic 8-bit control.
Traditional methods for managing carrier wave propagation, such as relays, are not only costly but are also energy-hungry. To tackle this, Pitchappa’s team, in collaboration with researchers from the National University of Singapore and Nanyang Technological University, Singapore, have innovated by integrating vanadium dioxide (VO2) into their metasurfaces. VO2 is known for its ability to switch between being an insulator and a conductor at different temperatures.
Their design featured an intricately patterned surface divided into eight sections, each embedded with a VO2 patch. Adjusting the temperature of these patches alters their state, thereby manipulating how THz waves are bent by the metasurface. This capability allows for precise control over the wave's direction and intensity—essential for targeting signals exactly where needed in advanced 6G networks.
Pitchappa highlighted the key achievements of their work: "We've managed to steer beams across a frequency range of 0.4 to 0.8 THz, adapting the angles as required, and achieved high-resolution control over these angles."
Looking to the future, Pitchappa is optimistic about the application of their technology. "Our metasurface could be directly installed in front of high-gain THz transmitters/receivers, enabling wide-angle broadband beam steering,” remarked Pitchappa. “This will be crucial for the ubiquitous implementation of 6G communication links."
Such advancements can significantly enhance network coverage and circumvent issues with non-line-of-sight communications, propelling us towards a 6G future.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Microelectronics (IME).
