Impacts of Real Hands on 5G Millimeter-Wave Cellphone Antennas: Measurements and Electromagnetic Models

Penetration of cellphones into markets requires their robust operation in time-varying radio environments, especially for millimeter-wave communications. Hands and fingers of a human cause significant changes in the physical environments of cellphones, which influence the communication qualities to a large extent. In this paper, electromagnetic models of real hands and cellphone antennas are developed, and their efficacy is verified through measurements for the first time in the literature. Referential cellphone antenna arrays at $28$ and $39$~GHz are designed. Their radiation properties are evaluated through near-field scanning of the two prototypes, first in free space for calibration of the antenna measurement system and for building simplified models of the cellphone arrays. Next, radiation measurements are set up with real hands so that they are compared with electromagnetic simulations of the interaction between hands and simplified models of the arrays. The comparison showed a close agreement in terms of spherical coverage, indicating the efficacy of the hand and antenna array models along with the measurement approach. The repeatability of the measurements is $0.5$~dB difference in terms of cumulative distributions of the spherical coverage at the median level.

Ultrawideband Antenna Systems Embedded into a Load Bearing Wall for Connected Buildings

The importance of indoor mobile connectivity has increased during the last years, especially during the Covid-19 pandemic. In contrast, new energy-efficient buildings contain structures like low-emissive widows and multi-layered thermal insulations which all block radio signals effectively. To solve this problem with indoor connectivity, we study passive antenna systems embedded in walls of low-energy buildings. We provide analytical models of a load bearing wall along with numerical and empirical evaluations of ultrawideband back-to-back antenna spiral antenna system in terms of electromagnetic- and thermal insulation. The antenna systems are optimized to operate well when embedded into load bearing walls. Unit cell models of the antenna embedded load bearing wall, which are called {\it signal-transmissive walls} in this paper, are developed to analyze their electromagnetic and thermal insulation properties. We show that our signal-transmissive wall improves the electromagnetic transmission compared to a raw load bearing wall over a wide bandwidth of 3-8 GHz, covering most of the new radio frequency range 1 (NR FR1), without compromising the thermal insulation capability of the wall demanded by the building regulation.