data for publication

The 5G to 6G transition demands superior MIMO antennas capable of operating in the terabit class data rates, accurate positioning and joint sensing and communication in small equipment. The thick integration of antenna components in smartphones, wearables, vehicles and satellites results in high levels of electromagnetic coupling, poor isolation and low MIMO capacity. The target of this review is the decrease of mutual coupling and increase of isolation in the MIMO antennas of Sub 6 GHz to mmWave(24-100 GHz) and Terahertz (0.1-10 THz) frequencies with metasurface based applications. There are over 40 described designs which are systematically benchmarked regarding isolation, envelope correlation coefficient (ECC), diversity gain, and channel capacity loss. The types surveyed include metasurface and metamaterial unit cells, defected ground and fractal structures, decoupling networks, electromagnetic bandgap and parasitic structures, intelligent reflecting surfaces and artificial intelligence aided systems. In small scale (MIMO) systems, representative implementations have been shown to attain isolation of larger than 40dB, ECC of less than 0.001, and channel capacity loss less than 0.4 bits/s/Hz. These measurements of antenna level factors are compared with 3GPP Release 18/19 and ITU IMT performance standards, and limitations due to tolerance of fabrication, high price low-loss substrates, and limiting THZ measurement and standardization systems considered. It also summarizes the research direction on scalable low cost metasurface implementations, AI enabled design processes, and environmentally friendly high isolation MIMO hardware to be used in future implementations of 5G and 6G.