Electromagnetic-Thermal Analyses of Distributed Antennas Embedded into a Load Bearing Wall

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 windows 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 wideband 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 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 2.6-8 GHz, covering most of the cellular new radio frequency range 1, without compromising the thermal insulation capability of the wall demanded by the building regulation. Optimized antenna deployment is shown with 22 dB improvement in electromagnetic transmission through the load bearing wall.Comment: 9 pages, 13 figures, submitted to IEEE Transactions on Antennas and Propagatio

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.Comment: 11 pages, 17 figures, Journa

Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band

Design of multi-element antennas for small mobile terminals operating at higher frequencies remains challenging despite smaller antenna dimension and possibility of achieving electrically large separation between them. In this paper, the importance of the type of radiating elements operating at 3400-3600 MHz and their locations on the terminal chassis are highlighted. An isotropic radiation pattern that receives incoming signals from arbitrary directions is obtained by combining the radiation patterns of multiple antennas with localized chassis current distribution. Four multiport antennas configurations with two- and eight-element antennas are designed and evaluated experimentally in indoor propagation environments. Our proposed designs of multi-element antennas provide the highest MIMO channel capacity compared to their counterparts using antennas with less localized chassis current distribution, even in the presence of user's hand

Methods for measuring RF radiation properties of small antennas

In this work significant improvements for measurements of the radio-frequency (RF) radiation properties of small antennas have been proposed and investigated. The main focus is on electrically small antennas as used in mobile communications systems. The methods proposed and evaluated in this thesis allow the minimisation of the dimensions of measurement chambers, and the methods also allow pattern measurements with a minimised error from the RF feed cable and thus lower measurement uncertainty. The first two parts of the work relate to measurements performed in especially small chambers. The aim is to provide an alternative measurement environment to large, fully anechoic chambers in the special case of small antenna calibrations. The use of small chambers such as GTEM cells and small anechoic chambers is proposed. Both options have been constructed and investigated by both simulations and measurements. The results show that a GTEM cell allows the reliable measurement of the radiation pattern and 3-dB bandwidth of small antennas with a low directivity and a dynamic range of less than 20 dB. A small anechoic chamber with the largest dimension of 2.5 m was built during the work for this thesis. The results obtained when measuring the 3-D radiation pattern, efficiency and the gain of a small handset antenna in that small anechoic chamber show further that far-field measurements in such a small anechoic chamber does not result in greater measurement uncertainty than results obtained in conventional large anechoic chambers. Finally, the influence of the RF feed cables on the radiation characteristics of a small antenna under test has been reduced by a novel method. This method is based on a multi-frequency balun that efficiently suppresses the propagation of leakage and parasitic currents on the shielding of the RF feed cable. The effect of the balun has been thoroughly investigated by means of computer simulations and measurements with a prototype. Both the far field and the near field have been analysed to yield a comprehensive set of figures of merit, showing that the presented balun decreases the measurement uncertainty much better than other commonly used measures against cable effects, such as ferrite beads. The balun cannot only be used in radiation-pattern measurements in large or small anechoic chambers, but also in radio-channel measurements, in near-field scans and in Standard Absorption Rate (SAR) measurements.reviewe

Self-user shadowing effects of millimeter-wave mobile phone antennas in a browsing mode

In this paper a simulation method for estimating the shadowing effect of a human at millimeter-wave frequencies is presented. The shadowing effect is studied at 28 GHz and at 60 GHz for the case when a user holds a mobile phone. Both single-hand grip and two-hand grip browsing scenarios are studied with a dual-polarized mobile phone antenna. We use the integral equation method combined with a surface-impedance-based material model for the human. It is found that at 28 GHz the human body causes shadowing of up to 22 dB behind torso and head of the human, while at 60 GHz shadowing is up to 30 dB. On the other hand, in some other directions the human body effectively increases radiation by up to 5-10 dB through scattering and reflection. The novel method using a detailed human shadowing model is useful in evaluating mm-wave mobile terminal antenna performance in realistic multipath propagation environments.Peer reviewe

Improving the Patch based Crossovers by Parasitic Modes and a Sub-element Technique

Publisher Copyright: IEEEThis brief introduces new methodologies to design microstrip line crossovers on a high-speed interconnection circuit. The crossover is based on a simple square patch, which employs TM100 and TM001 to achieve mode orthogonality so that two sets of intersecting signals can transmit along microstrip lines with a high isolation. Compared with rectangular waveguide crossovers that employ high modes, namely TE102 and TE201, it shows advantages like a smaller size and easier manufacturing. Then, the relevant techniques for performance improvement, including radiation suppression and bandwidth widening, are studied for practical circuit designs. Finally, based on the sub-element technique, the study designs a controllable frequency response for two intersecting signals and miniaturization of patch based crossovers. Two examples are implemented, manufactured and measured to justify the validity of the sub-element technology. In addition, the design steps of this method are simplified compared with relying on full-wavesimulations entirely.Peer reviewe