With the introduction of 5G communication systems operating in the mm-wave frequency range, new opportunities in terms of multimedia services and applications will become available. For this to happen, several technical challenges from an antenna standpoint need to be addressed. The achievements of high-gain characteristics and agile beamforming with wide-scan capabilities are the main targets of the ongoing research on mm-wave antenna arrays. In this paper, an up-to-date overview of antenna array technology for wireless communications at mm-wave frequencies is given. Particular focus is put on the review of the state-of-the art and most advanced antenna array concepts for point-to-point and point-to-multipoint radio links at said frequencies. Various figures of merit are assessed for a comprehensive analysis and bench marking of the technical solutions investigated in the presented survey.

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In order to cope with the needs of fifth-generation (5G) cellular networks and beyond, phasedarray antenna systems operating at millimeter-wave (mm-wave) frequencies will be required. This makes the system design very complex. In order to create insight and agility in the design process, we propose a framework that visualises the requirements and trade-offs of 5G-and-beyond systems. Our literature survey uses this framework to compare state-of-the-art papers on Silicon-based beamforming integrated circuits (BFICs) operating in the mm-wave band. Three use-cases are analyzed: Base-stations (BSs), Gateways (GtWs) and User Terminals (UTs). Based on the framework, we explore which implementation fits best with each use-cases. In UT, space and power consumption are the main constraints. For BSs, the main constraint is in output power and noise figure (NF). Finally, in GtW applications there is more flexibility as it has a larger footprint than UT but doesn't necessarily need to cover the same link-budget constraints of BSs. One of the identified limitations throughout all the cases is the heat generation, which is seen as a major bottleneck in mm-wave phased arrays. Only a few of the references show proper modelling and simulations for heat transfer of the realized BFICs. Finally, a limitation in the BFICs is the output power. In order to realize a mm-wave link at least 13 dBm would be required at the input of each antenna element. Only few references meet this criterion, and only at saturation. Further, in order to achieve more than 13 dBm in back-off operation a higher power density would be required. This would imply a further increase of heat generation in the system.

Energy-efficiency is crucial for modern radio-frequency (RF) receivers dedicated to Internet of Things applications. Energy-efficiency enhancements could be achieved by lowering the power consumption of integrated circuits, using antenna diversity or even with an association of both strategies. This paper compares two wideband RF front-end architectures, based on conventional low-noise amplifiers (LNA) and low-noise transconductance amplifiers (LNTA) with N-path filters, operating with three transmission schemes: single antenna, antenna selection and singular value decomposition beamforming. Our results show that the energy-efficiency behavior varies depending on the required communication link conditions, distance between nodes and metrics from the front-end receivers. For short-range scenarios, LNA presents the best performance in terms of energy-efficiency mainly due to its very low power consumption. With the increasing of the communication distance, the very low noise figure provided by N-path LNTA-based architectures outperforms the power consumption issue, yielding higher energy-efficiency for all transmission schemes. In addition, the selected front-end architecture depends on the number of active antennas at the receiver. Hence, we can observe that low noise figure is more important with a few active antennas at the receiver, while low power consumption becomes more important when the number of active RF chains at the receiver increases.