Conclusion

Beam-steering is a key enabler for millimeter-wave terrestrial networks. With the introduction of 5G-Advanced and 6G networks in the coming years, commercialization of beam-steering antennas will enable the telecommunication industry to establish a new network infrastructure. We can classify beam-steering antennas for such networks into four categories as described in this article. These are (i) phased array antennas, (ii) quasi-optical systems, (iii) leaky-wave antennas, and (iv) metamaterials and metasurfaces. Each of these categories has their own set of merits and demerits in terms of complexity, bandwidth, cost, power requirements, and beam-steering capabilities. Table 1 compares and summarizes the four categories with these parameters. Even though beam-steering antenna technology has advanced significantly over time, there are still some key challenges that need to be addressed before they get incorporated into the network. To highlight a few, these challenges include (i) high complexity, cost of fabrication and power requirements for intelligent metasurfaces, (ii) out-of-band shadowing because of metasurfaces, (iii) power requirements of phased array antennas, and (iv) mass production of 3D-printed quasi-optical systems. Additional figures and links to videos can be found in the Supplementary Information.