The effect of antenna polarization and body morphology on the measurement uncertainty of a wearable multi-band distributed exposure meter

This paper studies the effect of antenna polarization on measurement uncertainty of a multi-band body-worn distributed exposure meter (BWDM). The BWDM is a device for assessing electromagnetic fields in real environments accurately. The BWDM consists of 8 nodes and is calibrated on the body for simultaneous measurement of the incident power density in four frequency bands. Each node contains an antenna that can have two potential antenna polarizations.The BWDM is calibrated on four human subjects in an anechoic chamber to determine its measurement uncertainty in terms of 68% confidence interval (CI68) of the on-body antenna aperture. The results show that using a fixed polarization of the antennas on body can lead to a different CI68 up to maximum 4.9 dB when worn by another person which is still 9.6 dB lower than the measurement uncertainty of commercial exposure meters

On-body calibration and measurements using a personal, distributed exposimeter for wireless fidelity

This paper describes the design, calibration, and measurements with a personal, distributed exposimeter (PDE) for the on-body detection of radio frequency (RF) electromagnetic fields due to Wireless Fidelity (WiFi) networks. Numerical simulations show that using a combination of two RF nodes placed on the front and back of the body reduces the 50% prediction interval (PI50) on the incident free-space electric-field strength E-RMS(free). Median reductions of 10 dB and 9.1 dB are obtained compared to the PI50 of a single antenna placed on the body using a weighted arithmetic and geometric average, respectively. Therefore, a simple PDE topology based on two nodes, which are deployed on opposite sides of the human torso, is applied for calibration and measurements. The PDE is constructed using flexible, dual-polarized textile antennas and wearable electronics, which communicate wirelessly with a Universal Serial Bus (USB) connected receiver and can be unobtrusively integrated into a garment. The calibration of the PDE in an anechoic chamber proves that the PI50 of the measured E-RMS(free) is reduced to 3.2 dB. To demonstrate the real-life usability of the wireless device, a subject was equipped with the PDE during a walk in the city of Ghent, Belgium. Using a sample frequency of 2 Hz, an average incident power density of 59 nW m(-2) was registered in the WiFi frequency band during this walk

Design and calibration of a mm-wave personal exposure meter for 5G exposure assessment in indoor diffuse environments

For the first time, a mm-wave personal exposure meter (mm-PEM) for the 5th generation of mobile networks (5G) exposure assessment in indoor diffuse fields is presented. The design is based on simulations and on-phantom calibration measurements in a mm-wave reverberation chamber (RC) at 60 GHz. The mm-PEM consists of an array of nine antennas on the body. Using the mm-PEM, the incident power density (IPD) is measured in the unloaded RC, for the antenna(s) on the phantom and RC loaded with phantom. The uncertainty of the mm-PEM is then determined in terms of its response, which is defined as the ratio of antenna aperture for the above measurement scenarios. Using nine antennas, the designed meter has a response of 1.043 (0.17 dB) at 60 GHz, which is very close to 1 (0 dB), the desired ideal response value. The mm-PEM measured an IPD of 96.6 W m(-2) at 60 GHz in the RC, for an input power of 1 W. In addition, the average absorption cross-section of the phantom is determined as 225 cm(2), which is an excellent agreement with its physical dimensions

Representativeness and repeatability of microenvironmental personal and head exposures to radio-frequency electromagnetic fields

The aims of this study were to: i) investigate the repeatability and representativeness of personal radio frequency-electromagnetic fields (RF-EMFs) exposure measurements, across different microenvironments, ii) perform simultaneous evaluations of personal RF-EMF exposures for the whole body and the head, iii) validate the data obtained with a head-worn personal distributed exposimeter (PDE) against those obtained with an on-body worn personal exposimeter (PEM). Data on personal and head RF-EMF exposures were collected by performing measurements across 15 microenvironments in Melbourne, Australia. A body-worn PEM and a head-worn PDE were used for measuring body and head exposures, respectively. The summary statistics obtained for total RF-EMF exposure showed a high representativeness (r(2) > 0.66 for two paths in the same area) and a high repeatability over time (r(2) > 0.87 for repetitions of the same path). The median head exposure in the 900 MHz downlink band ranged between 0.06 V/m and 0.31 V/m. The results obtained during simultaneous measurements using the two devices showed high correlations (0.42 < r(2) < 0.94). The highest mean total RF-EMF exposure was measured in Melbourne's central business district (0.89 V/m), whereas the lowest mean total exposure was measured in a suburban residential area (0.05 V/m). This study shows that personal RF-EMF microenvironmental measurements in multiple microenvironments have high representativeness and repeatability over time. The personal RF-EMF exposure levels (i.e. body and head exposures) demonstrated moderate to high correlations

Characterisation of spatial and temporal variability of RF-EMF exposure levels in urban environments in Flanders, Belgium

Personal exposure to Radio-Frequency Electromagnetic Fields (RF-EMFs) was studied using personal measurements in five different microenvironments in each of five cities (Brussels, Antwerp, Ghent, Bruges and Hasselt) in Flanders, Belgium. These measurements were carried out by two researchers using on-body calibrated personal exposimeters. In three out of the five studied cities (Brussels, Ghent and Bruges), temporal aspects of personal exposure to RF-EMFs were studied as well. Measurements during and outside of rush hours (7:00-9:15 and 16:30-19:00) were compared. Likewise, measurements were executed during night time and compared to the ones measured during working hours. Representativeness and repeatability of the measurement method was studied as well. The highest mean total exposure was found in Brussels (2.63 mW/m(2)), the most densely populated city in this study. However, we measured higher downlink exposure in Antwerp than in Brussels, which might be an effect of the stronger legislation on base stations in Brussels. The measurements and used protocol were found to be both repeatable over time (r = 0.95 for median total exposure) and representative for the studied microenvironments in terms of path selection (r = 0.88 for median total exposure). Finally, in 10 out of the 13 on-body calibrated frequency bands we found that the measurement devices underestimate the intensity of the incident RF-EMFs with median underestimations up to 68%

A Review on Opportunities to Assess Hydration in Wireless Body Area Networks

The study of human body hydration is increasingly leading to new practical applications, including online assessment techniques for whole body water level and novel techniques for real time assessment methods as well as characterization for fitness and exercise performance. In this review, we will discuss the different techniques for assessing hydration from electrical properties of tissues and their components and the biological relations between tissues. This will be done mainly in the context of engineering while highlighting some applications in medicine, mobile health and sports