For the first time to the best of our knowledge, this paper provides an overview of millimeter-wave (mmWave) 5G antennas for cellular handsets. Practical design considerations and solutions related to the integration of mmWave phased-array antennas with beam switching capabilities are investigated in detail. To experimentally examine the proposed methodologies, two types of mesh-grid phased-array antennas featuring reconfigurable horizontal and vertical polarizations are designed, fabricated, and measured at the 60 GHz spectrum. Afterward the antennas are integrated with the rest of the 60 GHz RF and digital architecture to create integrated mmWave antenna modules and implemented within fully operating cellular handsets under plausible user scenarios. The effectiveness, current limitations, and required future research areas regarding the presented mmWave 5G antenna design technologies are studied using mmWave 5G system benchmarks.

This paper describes a low-profile 2×2 Multi-Input Multi-Output (MIMO) antenna system that is fully functional over the entire Long-Term Evolution (LTE) spectrum 699–960 MHz (lower frequency spectrum) and 1710–2690 MHz (higher frequency spectrum) that is applicable to real-life metallic smartphone platforms. The presented methodology entails utilizing the longitudinal edges of the ground plane amid an extremely narrow ground clearance of 2 mm. The metallic frame of the smartphone is utilized along with a stub network to devise a reconfigurable coupled loop antenna topology. The proposed 2×2 MIMO antenna configuration is measured and confirmed to exhibit efficient Envelope Correlation Coefficient (ECC) (<0.5) and one of the highest radiation efficiencies to be reported in literature across the entire LTE spectrum.

Future electronics and Internet of Things devices with the capability of high-speed wireless communication will increasingly rely on efficient and intelligent antennas. However, conventional wireless communication systems for small wireless electronics devices suffer from low radiation efficiencies of miniaturized antennas implemented within less-than ideal locations and real estates. Here, we introduce the original concept of utilizing the entire transparent region of high-resolution organic light-emitting diode (OLED) touch displays to render an antenna that is invisible to the human eye. A transverse magnetic resonant mode antenna is formulated based on transparent conductive polymers, which are precisely realized using mesoscale formation of electromagnetic boundary conditions. Simultaneously, these electromagnetic patterns achieve optical invisibility. We show that the transparent antenna film can be integrated inside an OLED touch display and feature efficient radiation properties at 2.4 GHz. The presented theory and measurement studies of the fabricated prototype for smartwatch application for Wi-Fi and Bluetooth connectivity inspire a broader range of integration of microwave and display technologies.

For the first time, to the best of our knowledge, this paper reports a complete millimeter wave (mmWave) wireless system, which coherently utilizes polarization diversity, multi-input multioutput (MIMO), and beamforming technologies applicable for upcoming fifth generation wireless mobile terminals. Using an interdisciplinary approach across the entire layers constituting of antennas, RF architecture, and digital modem, the polarization of the presented mmWave beamforming antenna system dynamically adapts to the channel environments and MIMO transmission modes. Empirical investigations, which are taken under real-life environments, ascertain that implementing switchable dual-polarized array antennas can alleviate the complexity of the beam searching procedure and MIMO channelization. In addition, experimental results acquired from intensive system level tests indicate more than 22 dB averaged cross-polarization discrimination under polarized MIMO channel conditions at the 60 GHz band. The beam selection algorithm that can be easily implemented based on power metric is confirmed to feature a 99.5% accuracy in comparison with the optimal selection algorithm derived from the theoretical maximal capacity.

An energy-efficient 5G phased array incorporating a novel vertically-polarized (V-pol) endfire planar folded slot antenna (PFSA) for user devices (UE) is presented. First, we analytically amend existing mmWave hybrid beamforming architectures that have precluded the uniqueness of 5G antennas and UEs. The total power consumption of the derived switchable 5G UE antenna system is estimated to be reduced by approximately 70% in comparison to a recently reported fully digital mmWave 5G UE antenna system under identical conditions. This is attributed to the ability to deactivate certain RF chains based on the directive nature of antenna elements. The PFSA featuring a height profile of less than 1/9 λ0 is derived from a planar folded slot structure. The designed and fabricated 1 × 4 PFSA array features impedance bandwidth of approximately 4 GHz with a center frequency of 37-39 GHz and the gain of 7.7 dBi with antenna efficiency of 94.12% at 39 GHz. A mmWave 5G beamforming module is demonstrated using the presented energy efficient 5G beamforming architecture and V-pol endfire PFSA array. The fabricated module achieves a measured EIRP of 18.2 dBm and scanning range of ±50° in azimuth at 28 GHz.