A wireless communication scheme based on space- and frequency-division multiplexing using digital metasurfaces

Digitally programmable metasurfaces are of potential use in wireless multiplexing techniques because they can encode and transmit information without using traditional radio-frequency components such as antennas or mixers. Space–time-coding digital metasurfaces can, in particular, manipulate the propagation direction and harmonic power distribution of electromagnetic waves, making them suitable for space- and frequency-division multiplexing. However, while digital metasurfaces have been used for wireless communication, these systems could implement signal modulation only in the time domain. Here, we report a wireless communication scheme that uses space–time-coding digital metasurfaces to implement both space- and frequency-division multiplexing. By encoding space–time-coding matrices through multiple channels, digital messages can be directly transmitted to different users at different locations simultaneously, without the need for digital-to-analogue conversion and mixing processes. To illustrate this approach, we have built a dual-channel wireless communication system based on a two-bit space–time-coding digital metasurface and use it to transmit two different pictures to two users simultaneously in real time. Space–time-coding digital metasurfaces can be used to implement secure and low-cost space- and frequency-division multiplexing in a dual-channel wireless communication system.