RF-MEMS Technology and Beamforming in 5G: Challenges and Opportunities for a Pair with a Still Untapped Potential

The challenging characteristics addressed by the 5G standard rely on widespread coverage and services enabled by adaptive beamforming operated by cells and base stations. To this end, basic radio frequency (RF) components and systems are subjected to a constant push toward miniaturization, reconfigurability, frequency agility, and low-power consumption. In case of high-performance RF passives, these needs can be satisfied by RF-MEMS technology (i.e. RF-micro-electro-mechanical-systems), and this will be the starting point of this paper. In this paper, an overview concerning the state of the art of RF-MEMS components and compounds involved in beamforming networks is provided, with a special attention toward hybrid architectures as key feature of realistic massive-multiple-input-multiple-output (mMIMO) systems. In light of the current frontiers for RF-MEMS in the framework of hybrid architectures, switches, phase shifters, and an attenuator realized at Fondazione Bruno Kessler (FBK) are presented as suitable building blocks for future compact modules and beamforming architectures, in which RF-MEMS could play an effective and predominant role.