Beam Squint in Ultra-Wideband mmWave Systems: RF Lens Array vs. Phase-Shifter-Based Array
Sang Hyun Park, Byoungnam Kim, Dong Ku Kim, Linglong Dai, Kai‐Kit Wong, Chan‐Byoung Chae
Abstract
In this article, we discuss the potential of radio frequency (RF) lens for ultra-wideband millimeter-wave (mmWave) systems. In terms of the beam squint, we compare the proposed RF lens antenna with the phase-shifter-based array for hybrid beamforming. To reduce the complexities of fully digital beamforming, researchers have come up with RF lens-based hybrid beamforming. The use of mmWave systems, however, causes an increase in bandwidth, which gives rise to the beam squint phenomenon. We first find the causative factors for beam squint in the dielectric RF lens antenna. Based on the beamforming gain at each frequency, we verify that in a specific situation, RF lens can be free of the beam squint effect. We use 3D electromagnetic analysis software to numerically interpret the beam squint of each antenna type. Based on the results, we present the degraded spectral efficiency by system-level simulations with 3D indoor ray tracing. Finally, to verify our analysis, we fabricate an actual RF lens antenna and demonstrate the real performance using an mmWave, NI PXle, and software-defined radio system.