Full-duplex metasurface controls radiation and reflection

Researchers from Peking University and their collaborators reported a programmable full-duplex metasurface in National Science Review. According to the authors, the device controls radiation and reflection independently through one physical aperture, simultaneously, at the same frequency and polarization doi.org. The fabricated sample contains 32 controllable meta-atoms integrated with a substrate-integrated waveguide (SIW) and operates at 10.55 GHz doi.org.

Why radiation and reflection were coupled

Radiation–reflection-integrated (R2I) metasurfaces combine the functions of an antenna and a reflector in a single aperture. Their responses, however, generally remain coupled: configuring the surface for radiation constrains its behavior in reflection doi.org. This limits independent operation at the same time, frequency and polarization.

The authors use the spatial-spectral separation of the two channels. In their approach, based on orthogonal spatial-spectrum theory, deep-subwavelength sampling lets a binary coding sequence encode a broad range of spatial-frequency components. SIW-guided and free-space excitations introduce different spectral shifts, so the two modes sample largely separated regions of the coding spectrum. As a result, radiated and reflected wavefronts can be controlled through a common code doi.org.

Hardware and prototypes

In reflection mode, switching the PIN diodes between OFF and ON gives a phase difference of about 180°, represented by coding values 1 and -1. In radiation mode, the PIN-OFF state couples guided energy from the SIW into free space and produces strong radiation, while PIN-ON suppresses this coupling and gives weak radiation. The radiation coding values are 1 and 0, respectively doi.org.

Using these mode-dependent responses, the team implemented a multiplexed coding sequence that steered the radiated and reflected beams toward distinct angles. The measured far-field patterns agreed well with full-wave simulations doi.org.

Two prototypes were built on this platform, both with a single metasurface under identical operating conditions doi.org. The integrated detection and stealth prototype tracked a moving target while reducing its own electromagnetic signature. The integrated sensing and communication prototype supported wireless communication while estimating the direction of arrival of uplink signals. The authors report accurate sensing and reliable communication in these experiments doi.org.

Peking University metasurface controls radiated and reflected beams independently at 10.55 GHz

Why radiation and reflection were coupled

Hardware and prototypes

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