No abstract

User tracking has been an important aspect in wireless communications. Commonly, distributed apertures such as array antennas or multiple sensors are needed in wireless communication systems to achieve spatial resolutions for user tracking. Here it is proposed to realize the user tracking and wireless digital transmission simultaneously by using a single metasurface aperture. The reflection‐type metasurface consists of many subwavelength binary reconfigurable units. By programming these binary units, the metasurface can steer waves radiated from a horn antenna to a specified direction with different digital radiation phases. With this function, the metasurface can track the users by steering directional beams and transmit phase‐modulated digital signals through the directional beams. A prototype based on a programmable metasurface is developed and experiments in terms of cyclic redundancy check (CRC) and constellation diagrams are performed. The measured results prove that the user tracking and wireless digital transmission can be integrated through the programmable metasurface. Considering the simple architecture and flexible controlling features, the proposed methodology has great application prospect in integrated radar‐communication systems and cognitive electronic systems.

By dynamically configuring unit structures, a digital programmable metasurface (DPM) can perform space, time, and frequency modulations of electromagnetic (EM) waves directly on the aperture, and hence linking the metasurface physics to digital information worlds. However, the interactions between DPMs and EM waves have not yet been systematically and efficiently depicted. Based on the Huygens-Fresnel principle and Fourier analysis, here the authors demonstrate the foundations of space-time-frequency joint controls of monochromatic or nonmonochromatic EM waves by DPM. Due to linear superposition properties of Fourier transform in the analysis, the space-and time-frequency modulations are naturally decoupled, hence enabling simultaneous and independent space-time-frequency controls of the EM waves. A transmissive DPM is designed and fabricated to interpret the space-time-frequency joint modulations. This work will facilitate the researches on DPMs and promote the applications of DPMs in wireless communications, intelligent sensing, and radar systems.

Commonly, phased array antennas are used to provide spatial resolution for direction of arrival (DOA) estimations. However, the phase‐array‐based DOA estimations usually require complicated system architecture and signal processing. Digital programmable metasurfaces (DPMs) can realize flexible spatial modulations of electromagnetic (EM) waves without using massive transceivers, and hence can be used for DOA estimations with much simplified architectures. Here, a mechanism of DPM‐based DOA estimations at Ka band is proposed. A reflective DPM is designed to produce a series of dual beams in random, so as to establish a sensing matrix and sample the incident wave. Orthogonal matched pursuit algorithm is used to estimate DOA from the sparsely sampled datasets. The performances of the DPM‐based DOA estimations are demonstrated by simulations and experiments for the cases of single source and double sources. This work promotes the development of DPMs and is expected to find important applications in radar and wireless communication systems, as well as the joint radar and communication systems.

As an important bridge between the human brain and external devices, the brain−computer interface (BCI) has received much attention for decades. To further explore the connection between the human brain signals and electromagnetic (EM) information, here we propose a brain−computer−metasurface holography (BCMH) system to enable the brain control of EM imaging. By using a P300-based BCI and a 1-bit programmable metasurface, BCMH can precisely reproduce specific EM holographic images according to the operator's intentions. Twenty distinct images are designed and tested with BCMH, showing good consistency with the theoretical expectation. The proposed BCMH, integrating the EM manipulation capability with intelligence of the human brain, may provide a new paradigm of interactions among the human, intelligent metasurfaces, and machines, and hence promote the visual-reality (VR) technology.