RF Lens-Embedded Antenna Array for mmWave MIMO: Design and Performance

The requirement of high data rate in 5G calls for utilization of the mmWave frequency band. Researchers seeking to compensate for mmWave's high path loss have proposed that mmWave MIMO systems make use of beamforming. Hybrid beamforming systems demonstrate promising performance in achieving high gain and directivity by using phase shifters. The actual implementation, however, is costly and complex. To reduce such cost and complexity, this article presents actual prototypes of the lens antenna to be used in 5G mmWave beamforming systems. Using a lens as a passive phase shifter enables beamforming without the heavy network of phase shifters, while gain and directivity are achieved by the energy-focusing property of the lens. Proposed in this article are two types of lens antennas, one for static and the other for mobile usage. The lens antennas' sizes are varied to also discuss the lens design. Their performance is evaluated using measurements and simulation data along with link- and system-level analysis. Results show the lens antenna yields high gain, directivity, and improved beam-switching feasibility compared to when a lens is not used.