Reconfigurable intelligent surface:design the channel-a new opportunity for future wireless networks

In this paper,we survey state-of-the-art research outcomes in the burgeoning field of Reconfigurable Intelligent Surface(RIS),given its potential for significant performance enhancement of next-generation wireless communication networks by means of adapting a propagation environment.Emphasis has been placed on several aspects gating the commercial viability of future network deployment.Comprehensive summaries are provided for practical hardware design considerations and broad implications of artificial intelligence techniques,as are in-depth outlooks on the salient aspects of system models,use cases,and physical layer optimization techniques.

Recent Developments of Transmissive Reconfigurable Intelligent Surfaces:A Review

Reconfigurable intelligent surface(RIS)is considered as one of the key technologies for the next-generation mobile communication systems.The transmissive RIS is able to achieve dynamic beamforming capability while transmitting an in-band RF signal through its aper-ture,and has promising prospects in various practical application scenarios.This paper reviews some of the latest developments of the trans-missive RIS.The approaches for transmissive RIS designs are classified and described briefly.Numerous designs with different phase resolu-tions,such as 1-bit,2-bit or continuous 360°phase shifts,are presented,with detailed discussions on their operating mechanisms and trans-mission performances.The design solutions for various transmissive RIS elements are summarized and compared.

Bi-Function Multi-Beam Graphene Lens Antenna for Terahertz Applications

Bi-function Compact graphene lens antenna in terahertz (THz) band has been investigated. The array function is switched between two status, reflectarray and/or transmitarray. The tunability of graphene conductivity introduces the bi-function characteristics of a single array structure in the THz band. The design depends on changing the graphene DC biasing voltage to transform the transmitting antenna to reflecting antenna. The compact structure of the antenna array saves the cost and the allocation area for the terahertz communication applications. A 13 × 13 reflectarray/ transmitarray antenna covering an area of 364 × 364 μm2 is proposed. A dual-beams reflectarray/transmitarray antenna is achieved by rearranging the cell elements of the array successively. Finally, a single structure is used to work as reflectarray and transmitarray antenna at the same time by rearranging the applied voltages between the different pieces of the graphene sheet using chess board arrangement. The phases of the successive unit-cells are kept the same of their locations in the original full array. The radiation characteristics of the array are investigated using the CST Microwave Studio for the bi-function operation.

Reconfigurable Metasurface:A Systematic Categorization and Recent Advances

Considering the rapid progress of theory,design,fabrication and applications,metasurfaces(MTSs)have become a new research frontier in microwave,terahertz and optical bands.Reconfigurable metasurfaces(R-MTSs)can dynamically modulate electromagnetic(EM)waves with unparalleled flexibility,which has led to a great surge of research in recent years.Numerous R-MTSs with powerful capabilities and various functions are being proposed explosively.Based on the five dimensions of EM waves,this review proposes a unified model to describe the interactions among R-MTSs,EM waves and EM information and suggests an information bit allocation strategy to categorize different types of R-MTSs systematically.Recent advances in R-MTSs and 1-bit and 2-bit elements manipulating different wave dimensions are reviewed in detail.Finally,this review discusses the future research trends of R-MTSs.R-MTSs with diverse dimensions and functions may propel the next generation of communication,detection,sensing,imaging and computing applications.