PMID- 35208409
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20230917
IS  - 2072-666X (Print)
IS  - 2072-666X (Electronic)
IS  - 2072-666X (Linking)
VI  - 13
IP  - 2
DP  - 2022 Feb 10
TI  - Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links.
LID - 10.3390/mi13020285 [doi]
LID - 285
AB  - The forthcoming sixth generation (6G) communication network is envisioned to 
      provide ultra-fast data transmission and ubiquitous wireless connectivity. The 
      terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great 
      potential for 6G wireless technologies. However, the THz links suffers from high 
      loss and line-of-sight connectivity. To overcome these challenges, a 
      cost-effective method to dynamically optimize the transmission path using 
      reconfigurable intelligent surfaces (RISs) is widely proposed. RIS is constructed 
      by embedding active elements into passive metasurfaces, which is an artificially 
      designed periodic structure. However, the active elements (e.g., PIN diodes) used 
      for 5G RIS are impractical for 6G RIS due to the cutoff frequency limitation and 
      higher loss at THz frequencies. As such, various tuning elements have been 
      explored to fill this THz gap between radio waves and infrared light. The focus 
      of this review is on THz RISs with the potential to assist 6G communication 
      functionalities including pixel-level amplitude modulation and dynamic beam 
      manipulation. By reviewing a wide range of tuning mechanisms, including 
      electronic approaches (complementary metal-oxide-semiconductor (CMOS) 
      transistors, Schottky diodes, high electron mobility transistors (HEMTs), and 
      graphene), optical approaches (photoactive semiconductor materials), phase-change 
      materials (vanadium dioxide, chalcogenides, and liquid crystals), as well as 
      microelectromechanical systems (MEMS), this review summarizes recent developments 
      in THz RISs in support of 6G communication links and discusses future research 
      directions in this field.
FAU - Yang, Fengyuan
AU  - Yang F
AD  - Institute of Microelectronics, Agency for Science, Technology and Research, 
      Singapore 138634, Singapore.
FAU - Pitchappa, Prakash
AU  - Pitchappa P
AUID- ORCID: 0000-0002-6168-4130
AD  - Institute of Microelectronics, Agency for Science, Technology and Research, 
      Singapore 138634, Singapore.
FAU - Wang, Nan
AU  - Wang N
AUID- ORCID: 0000-0003-1285-7530
AD  - Institute of Microelectronics, Agency for Science, Technology and Research, 
      Singapore 138634, Singapore.
LA  - eng
GR  - A18A5b0056/Science and Engineering Research Council of A*STAR (Agency for 
      Science, Technology and Research), Singapore/
PT  - Journal Article
PT  - Review
DEP - 20220210
PL  - Switzerland
TA  - Micromachines (Basel)
JT  - Micromachines
JID - 101640903
PMC - PMC8879315
OTO - NOTNLM
OT  - 6G communication
OT  - reconfigurable intelligent surface (RIS)
OT  - reconfigurable metasurface
OT  - terahertz (THz)
COIS- The authors declare no conflict of interest.
EDAT- 2022/02/26 06:00
MHDA- 2022/02/26 06:01
PMCR- 2022/02/10
CRDT- 2022/02/25 01:14
PHST- 2022/01/14 00:00 [received]
PHST- 2022/02/02 00:00 [revised]
PHST- 2022/02/04 00:00 [accepted]
PHST- 2022/02/25 01:14 [entrez]
PHST- 2022/02/26 06:00 [pubmed]
PHST- 2022/02/26 06:01 [medline]
PHST- 2022/02/10 00:00 [pmc-release]
AID - mi13020285 [pii]
AID - micromachines-13-00285 [pii]
AID - 10.3390/mi13020285 [doi]
PST - epublish
SO  - Micromachines (Basel). 2022 Feb 10;13(2):285. doi: 10.3390/mi13020285.