A radar antenna is designed to find targets, yet the waves it reflects can also reveal its own presence. Wireless devices face a related challenge, communicating with users while sensing their surroundings. Both tasks raise a common question: how can a single surface independently control the waves it emits and the waves it reflects?
In a new study published in National Science Review, researchers from Peking University and their collaborators report a programmable full-duplex metasurface that addresses this challenge. The device independently controls radiation and reflection through the same physical aperture, simultaneously at the same frequency and polarization. This capability brings together antenna and reflector functions while allowing each response to be shaped separately.
Metasurfaces are ultrathin arrays of engineered subwavelength elements that manipulate electromagnetic wavefields. Programmable metasurfaces with active elements like PIN diodes or varactors enable dynamic reconfiguration of their electromagnetic responses. Radiation–reflection-integrated (R 2 I) metasurfaces combine radiation and reflection within a single physical aperture. However, their responses generally remain coupled: configuring the surface for radiation constrains its behavior in reflection. This coupling limits independent operation at the same time, frequency and polarization.
The researchers resolve this conflict by exploiting the spatial-spectral separation between the radiation and reflection channels. Their approach follows orthogonal spatial-spectrum theory, in which deep-subwavelength sampling allows a binary coding sequence to encode a broad range of spatial-frequency components. SIW-guided and free-space excitations introduce different spectral shifts, causing the two modes to sample largely separated regions of the coding spectrum. Different spatial-frequency components therefore predominantly govern radiation and reflection, enabling independent control of both wavefronts through a common code on the same physical aperture.
To validate this principle, the team fabricated a full-duplex programmable metasurface comprising 32 controllable meta-atoms integrated with an SIW, operating at 10.55 GHz. In reflection mode, switching the PIN diodes between the OFF and ON states produces an approximately 180° phase difference, represented by coding values 1 and -1. In radiation mode, the PIN-OFF state couples guided energy from the SIW into free space, producing strong radiation. The PIN-ON state suppresses this coupling, producing weak radiation. The corresponding radiation coding values are 1 and 0, respectively. The researchers used these mode-dependent responses to implement a multiplexed coding sequence that simultaneously steered the radiated and reflected beams towards distinct spatial angles. The measured far-field patterns agreed well with full-wave simulations, validating independent control of both wavefronts through the shared aperture.
Building on this hardware platform, the researchers developed prototypes for integrated detection and stealth (IDAS) and integrated sensing and communication (ISAC). The IDAS prototype tracked a moving target while reducing its own electromagnetic signature. The ISAC prototype supported wireless communication while simultaneously estimating the direction of arrival of uplink signals. Experimental results demonstrated accurate sensing and reliable communication, validating the effectiveness of the proposed full-duplex platform.
This platform could reshape next-generation radar and wireless systems, enabling target detection with reduced observability and simultaneous sensing and communication through a single aperture. Looking further ahead, extending the design to two-dimensional arrays, multi-bit coding and millimeter-wave frequencies could unlock more versatile electromagnetic skins that dynamically coordinate radiation and reflection. Such advances could turn the surfaces of future information systems into programmable interfaces for sensing, communication and electromagnetic signature control.
National Science Review