Metasurfaces have shown their great capability to manipulate electromagnetic waves. As a new concept, reconfigurable metasurfaces attract researchers’ attention. There are many kinds of reconfigurable components, devices and materials that can be loaded on metasurfaces. When cooperating with reconfigurable structures, dynamic control of the responses of metasurfaces are realized under external excitations, offering new opportunities to manipulate electromagnetic waves dynamically. This review introduces some common methods to design reconfigurable metasurfaces classified by the techniques they use, such as special materials, semiconductor components and mechanical devices. Specifically, this review provides a comparison among all the methods mentioned and discusses their pros and cons. Finally, based on the unsolved problems in the designs and applications, the challenges and possible developments in the future are discussed.

This letter proposes an ultra-wideband 1-bit suspended reconfigurable intelligent surface (RIS) designed to enhance the signal coverage of wireless communication networks. The RIS unit cell comprises two metal gratings connected via a PIN diode, a dielectric-air-dielectric interlayer, and a metal reflective layer. The RIS achieves a stable reflection phase difference of 180° ± 30° between the ON and OFF states of the PIN diode within the ultra-wideband range of 2.75–6 GHz. This range includes the 3.4 GHz and 4.9 GHz bands for 5G communication, the 5.2 GHz band for indoor wireless communication, and the 5.8 GHz band for Wi-Fi and Bluetooth signals. A prototype, consisting of 20 × 20 unit cells, was fabricated and measured, demonstrating two-dimensional wide-angle beam scanning of ± 60° within the working frequency range. Furthermore, a RIS-assisted wireless communication system was constructed, confirming that deploying RIS can significantly enhance communication quality in targeted areas by transmitting and receiving image information at different frequencies. The proposed RIS holds substantial potential for RIS-assisted wireless communication systems.

A reflective reconfigurable metasurface (RM) with stable amplitude and full phase modulation based on guided-wave- driven structure is proposed, which can be used for dynamic real-time beam deflection and scanning in practical communication. The guided-wave-driven metasurface is composed of a coupling-waveguide-decoupling topology. By changing the bias voltages of varactor diodes in unit cells, the phase of the two orthogonal linearly-polarized modes is modulated. To verify the performance of proposed RM, a prototype consisting of 9 × 9 unit cells was fabricated and measured. The measured results show that the RM can achieve dynamic beam deflection with a scanning range of ±60° at 2.6 GHz. This beam scanning capability can be achieved in dual-polarized modes, which provides broad application prospects for wireless communication systems.

In this paper, a guided-wave inspired dual-polarized reconfigurable intelligent surface (RIS) with low cross-polarization level is proposed. The designed RIS unit cell is mainly composed of a metal patch, two 180° hybrid couplers, and two phase modulation circuits from top to bottom. The top square metal patch loaded with four parasitic strips is used to convert the incident electromagnetic wave and guided-wave to each other; the middle 180° hybrid couplers are used to differentially feed the square patch to greatly reduce the cross-polarization level; the bottom phase modulation circuits are used to modulate the phase of guided-wave by applying different bias voltages. The designed unit cell can achieve a continuous full phase modulation, with a reflection amplitude fluctuation range of less than 0.8 dB and a cross-polarization level below −27 dB at the working frequency of 4.9 GHz. As validation, a RIS sample consisting of 8 × 8 unit cells is fabricated and measured, and the measured results are in agreement with the simulated results. By providing different bias voltages to each unit cell through a field programmable array (FPGA), the reflected beam can scan in a two-dimensional range of ±60° at 4.9 GHz. The proposed RIS has great application potential in the RIS-assisted wireless communication systems.