Experimental evaluation of modular antenna arrays at 28 GHz under the presence of human body
Loading...
URL
Journal Title
Journal ISSN
Volume Title
Sähkötekniikan korkeakoulu |
Master's thesis
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
2019-10-21
Department
Major/Subject
Radio Science and Engineering
Mcode
ELEC3038
Degree programme
Master’s Programme in Electronics and Nanotechnology (TS2013)
Language
en
Pages
59+13
Series
Abstract
The goal of this thesis is to develop and test an experimental method for characterising antenna arrays for mobile phones at 28 GHz under the presence of the user. Previous studies were based merely on computer simulations, or on measurements with actual humans, where repeatability is an unsolved issue. Antenna measurements with a human phantom have now been carried out and analysed for the first time. For their validation, simulation methods for characterising mm-wave mobile phone antennas under the presence of a human body, and the detailed evaluation process are presented here, including spherical coverage and total array gain. Utilising the presented simulation methods, a simplified human phantom is designed, validated, and manufactured. The electrical properties of human tissues are well known, and different material recipes to mimic human skin were reported in previous studies. Based on these, we created a polyethylene-based skin-like material with electrical properties similar as in human skin. This material was used as a surface for the final human phantom. This phantom was then used in radiation-pattern measurements at 28 GHz. Two planar 2x2 dual-polarised antenna arrays were designed and manufactured. As expected, the design of the microstrip-feed line network was crucial in the design of the antenna arrays, especially the mutual coupling needs to be low to ensure the designed operation of the arrays. Antenna radiation pattern measurements, both in free space and with the human phantom, were carried out in an anechoic chamber. The losses of feed cables and connectors were de-embedded by calculating suitable amplitude correction terms that normalize differences between measured and simulated free-space element patterns. The phantom measurements were performed with both antenna arrays, and after mathematical beam-forming with a suitable amount of element-phasing cases, the spherical coverage of each array was calculated. Element radiation patterns and spherical coverage of both antenna arrays under the presence of the human phantom were compared to the simulations. In the spherical coverage CDFs of both arrays, the difference between measured and simulated peak gain is 1 - 2 dB, and the difference between measured and simulated median gain level is 0.6 - 2 dB. This comparison shows that the proposed experimental method for characterising mm-wave mobile antenna arrays in the presence of the user is feasible. One test array also was measured twice with the phantom and the maximum difference between spherical coverage CDFs was 1 dB proving good repeatability of the proposed experimental method.Description
Supervisor
Haneda, KatsuyukiThesis advisor
Icheln, ClemensKeywords
mobile antennas, human phantom, skin material, antenna evaluation, millimeter waves