Modeling and Measurements of Human Body Effects on Millimeter-Wave and Sub-Terahertz Handset Antenna Radiation: From Permittivity Estimation to Spherical Coverage

As the demand for high data-rate telecommunications continues to grow, the limitations of the sub-6 GHz band become increasingly apparent, particularly due to its constrained bandwidth. In response, fifth-generation (5G) millimeter-wave (mmW) and sub-terahertz (sub-THz) frequencies have emerged as promising solutions, offering unprecedented data rates thanks to their wide bandwidth. However, electromagnetic waves at these higher frequencies experience more significant free-space path loss and are more easily obstructed by blockages, presenting substantial challenges in maintaining reliable, low-latency wireless channels. To understand and predict how wireless signals behave in complex environments, modeling wireless channels is essential. A key challenge in modeling these channels at high frequencies is accurately representing user-induced blockages, such as the effects of a user’s body and hands on handset antennas. Hand blockages involve complex near-field interactions with handset antennas, often requiring full-wave simulations for accurate analysis. Although these simulations are effective for modeling body blockages, they are highly time-consuming. The plane wave assumption, typically valid for free-space electromagnetic waves, does not apply to electromagnetic waves traveling through body blockages, which fall within the Fresnel region of handset antennas. Consequently, developing a reliable, computationally efficient model of human-antenna interactions for wireless channel modeling is critical. In the 5G mmW bands, this thesis presents a detailed study of hand effects on handset antennas. Measured radiation patterns using real hands and hand phantom models validate full-wave simulation models of hand-antenna interactions. Additionally, an analytical model based on knifeedge diffraction and geometric optics is introduced to estimate user body effects, offering a faster alternative to full-wave simulations with comparable spherical coverage predictions. In the sub-THz bands, novel permittivity characterization methods for thin and thick materials address phase calibration challenges in free-space measurements. Human skin permittivity is characterized using open-ended waveguides for small areas and free-space reflection coefficients for larger areas. These human skin permittivity data support the development of simulation models for analyzing hand effects on sub-THz handset antennas. Radiation pattern measurements using the proposed reference antennas and real hands validate the hand-antenna simulation models. Looking forward, these validated models provide a foundation for future research on hand effects in handset antenna design and wireless channel modeling. The proposed measurement methodologies will also support further experimental studies on hand-antenna interactions and material permittivity characterization, contributing to more accurate modeling of wireless channels at high frequencies.