A novel antenna bringing us closer to 6G wireless communications

Space-time coding can alter the direction, frequency, and amplitude of the electromagnetic waves from the new-generation antenna.
Kavita Verma


A new antenna system leveraging space-time coding technology to enhance security for 6G wireless communications is on the horizon. 

A research team led by a scientist at CityU has resulted in an innovative, game-changing antenna. This revolutionary invention allows unprecedented control of the direction, frequency, and intensity of its signal beam emission. On top of that, this antenna is invaluable for 6G wireless communications applications such as ISAC sensing and communication integration.

The role of Space-time Coding(STC)

Once fabricated, the characteristics and structure of the traditional antennas are almost impossible to change. 

However, space-time coding can alter the direction, frequency, and amplitude of the electromagnetic waves from the new-generation antenna, known as a "sideband-free (STC) metasurface antenna." This enables great flexibility for users. 

This revolutionary feature utilizes metasurfaces – special ultra-thin materials made of many tiny meta-atoms. This can be done by manipulating the current to power them to switch the meta-atoms between radiating and non-radiating states – acting like an array of switches modifying its response in real time!

The STC metasurface antenna can harness and manipulate complicated electromagnetic waves in space and frequency domains by utilizing software control. This enables it to generate a precisely tailored beam with any desired radiation pattern.

Successful combination of two research advances

Professor Chan Chi-Hou, Chair Professor of Electronic Engineering and an Acting Provost at CityU, confirmed that the antenna is a successful collaboration of space-time coding techniques and amplitude-modulated (AM) leaky wave antennas. 

In 2020, the AM leaky-wave antennas concept was first proposed by Dr. Wu Geng at CityU, a postdoctoral fellow in the State Key Laboratory of Terahertz. This concept offers an analytical method for creating antennas with the necessary emission patterns for various niche applications by merely altering the antennas' structure and form.

Dr.Junyan Dai, a leading expert in space-time coding and digital metasurfaces for reconfiguring antenna performance, joined the research group of Professors Cui Tiejun and Cheng Qiang from Southeast University's Nanjing campus. 

At around that same time, Dr. Dai also came to CityU (known for many research studies and discoveries), where he teamed up with Professor Chan at The School of Knowledge Innovation Technology (SKIT)

His skillset gave an exciting new dimension to their research – once fabricated, these AM leaky wave antennas display fixed radiation characteristics which can now be dynamically changed thanks to his innovative work.

Professor Chan and his team unveiled a revolutionary new design – utilizing waveguides to control electromagnetic waves on metasurfaces. This breakthrough eliminated unwanted harmonic frequencies, referred to as 'spectrum pollution', while increasing the antenna's directivity beam for secure communication. By taking advantage of reflection between an inner wall, they've opened up possibilities in wireless transmission never seen before!

STC and AM technologies play an important role in the ISAC for 6G wireless communications

With both technologies, the scientists were able to achieve the designated radiation characteristics. These characteristics can be controlled by the on-off duration and sequences on the switches on the antenna through STC. 

Professor Chan's amazing innovation harnesses the power of a RADAR-like STC metasurface antenna, allowing it to focus its energy into a single point with adjustable or fixed focal lengths. 

This could be used in ISAC for 6G wireless communications not only to create 3D holograms that let users talk face-to-face through their mobile phones but also to provide superior protection against eavesdropping than traditional transmitter architecture.

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