Matthias Van den Bossche

A Multi-Band Body-Worn Distributed Radio-Frequency Exposure Meter: Design, On-Body Calibration and Study of Body Morphology

A multi-band Body-Worn Distributed exposure Meter (BWDM) calibrated for simultaneous measurement of the incident power density in 11 telecommunication frequency bands, is proposed. The BDWM consists of 22 textile antennas integrated in a garment and is calibrated on six human subjects in an anechoic chamber to assess its measurement uncertainty in terms of 68% confidence interval of the on-body antenna aperture. It is shown that by using multiple antennas in each frequency band, the uncertainty of the BWDM is 22 dB improved with respect to single nodes on the front and back of the torso and variations are decreased to maximum 8.8 dB. Moreover, deploying single antennas for different body morphologies results in a variation up to 9.3 dB, which is reduced to 3.6 dB using multiple antennas for six subjects with various body mass index values. The designed BWDM, has an improved uncertainty of up to 9.6 dB in comparison to commercially available personal exposure meters calibrated on body. As an application, an average incident power density in the range of 26.7–90.8 μW·m−2 is measured in Ghent, Belgium. The measurements show that commercial personal exposure meters underestimate the actual exposure by a factor of up to 20.6.

Measurements of intermediate-frequency electric and magnetic fields in households

&NA; Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely‐low‐frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate‐frequency (IF) range (300 Hz to 1 MHz) as well as potential effects of IF fields on the human body remains limited, although the range of household appliances with electrical components working in the IF range has grown significantly (e.g., induction cookers and compact fluorescent lighting). In this study, an extensive measurement survey was performed on the levels of electric and magnetic fields in the IF range typically present in residences as well as emitted by a wide range of household appliances under real‐life circumstances. Using spot measurements, residential IF field levels were found to be generally low, while the use of certain appliances at close distance (20 cm) may result in a relatively high exposure. Overall, appliance emissions contained either harmonic signals, with fundamental frequencies between 6 kHz and 300 kHz, which were sometimes accompanied by regions in the IF spectrum of rather noisy, elevated field strengths, or much more capricious spectra, dominated by 50 Hz harmonics emanating far in the IF domain. The maximum peak field strengths recorded at 20 cm were 41.5 V/m and 2.7 A/m, both from induction cookers. Finally, none of the appliance emissions in the IF range exceeded the exposure summation rules recommended by the International Commission on Non‐Ionizing Radiation Protection guidelines and the International Electrotechnical Commission (IEC 62233) standard at 20 cm and beyond (maximum exposure quotients EQE 1.0 and EQH 0.13). HighlightsSurvey of residential electric and magnetic fields at intermediate frequencies (IF).IF‐EF and ‐MF emitted by 280 household appliances were characterised.Strongest emitters were induction cookers, CFLs, LCD‐TVs, and microwave ovens.No emissions exceeded ICNIRP limits (highest exposure quotient was 1.00).

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

Abstract 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 (r2 > 0.66 for two paths in the same area) and a high repeatability over time (r2 > 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 < r2 < 0.94). The highest mean total RF‐EMF exposure was measured in Melbournes 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. HighlightsFirst time assessment of head exposure to RF‐EMF in uncontrolled environments, in 15 microenvironments in Melbourne, Australia.We show that our measurement protocol is repeatable over time.We show that the paths selected in our protocol are representative for the larger areas in which they are defined.Exposure to RF‐EMF is higher in more dense urban areas than in less populated suburban areas in the outskirts of the city.

In situ exposure assessment of intermediate frequency fields of diverse devices.

In this study, in situ exposure assessment of both electric and magnetic fields of different intermediate frequency (IF) sources is investigated. The authors investigated smart boards and touchscreens, energy-saving bulbs, fluorescent lamps, a portable hearing unit and an electrosurgical unit (ESU). For most of these sources, the electric field is the dominating quantity. International Commission on Non-Ionizing Radiation Protection reference levels are exceeded for touchscreens (44 kHz: up to 155.7 V m(-1) at 5 cm), energy-saving bulbs (38-52 kHz: up to 117.3 V m(-1)), fluorescent lamps (52 kHz: up to 471 V m(-1) at 5 cm) and ESUs (up to 920 kHz: 792 V m(-1) at 0.5 cm). Magnetic field strengths up to 1.8 and 10.5 A m(-1) were measured close to the ESU and portable hearing unit (69 V m(-1)), respectively. Large differences of measured field values exist among the various operating modes of the IF equipment. Compliance distances for general public range from 15.3 cm (touchscreen) to 25 cm (fluorescent lamps).

Exposure assessment of microwave ovens and impact on total exposure in WLANs

In situ exposure of electric fields of 11 microwave ovens is assessed in an occupational environment and in an office. Measurements as a function of distance without load and with a load of 275 ml of tap water were performed at distances of <1 m. The maximal measured field was 55.2 V m(-1) at 5 cm from the oven (without load), which is 2.5 and 1.1 times below the International Commission on Non-Ionizing Radiation Protection reference level for occupational exposure and general public exposure, respectively. For exposure at distances of >1 m, a model of the electric field in a realistic environment is proposed. In an office scenario, switching on a microwave oven increases the median field strength from 91 to 145 mV m(-1) (+91 %) in a traditional Wireless Local Area Network (WLAN) deployment and from 44 to 92 mV m(-1) (+109 %) in an exposure-optimised WLAN deployment.

Design and calibration of a wearable personal distributed exposimeter for LTE 800-2600 MHz downlink bands

For the first time, a wearable personal distributed exposimeter (WPDE) is designed and calibrated for the Long-Term Evolution (LTE) 800 and 2600 MHz downlink bands. The proposed WPDE has a 68% confidence interval of 4.8–5.6 dB for different number of antennas and polarizations. Measurements of the WPDE are compared and validated with a commercial exposimeter in a real environment.

Exposure to electric and magnetic fields at intermediate frequencies of household appliances

Human exposure to electric and magnetic fields has been amply investigated in the extremely-low frequency (ELF) and radiofrequency (RF) ranges. However, research on typical emissions in the intermediate-frequency (IF) range remains limited. In this study, an extensive measurement survey was performed on the levels of electric and magnetic fields at intermediate frequencies typically emitted by a wide range of household appliances. The emissions contained either harmonic signals, with fundamental frequencies between 6 kHz and 100 kHz, or much more capricious spectra, dominated by 50 Hz harmonics emanating far in the IF domain. Use of appliances at close distance (20 cm) of certain appliances may result in a relatively high exposure, but no appliances IF emissions exceeded the ICNIRP2010 exposure summation rule (maximum electric- and magnetic-field exposure quotients were respectively 1.00, for a compact fluorescent lamp, and 0.13, for an induction cooker).

Wearable multi-antenna multi-band measurement system for personal radio-frequency exposure assessment

Rising concern about the potential harmfulness of human radio-frequency exposure causes scientists to be highly interested in measuring these exposure levels. The set of measured signal levels on a map of locations is then used for epidemiological research, looking for correlation to the incidence of certain illnesses. Currently available hand-held exposimeters have the disadvantage that the measured signal levels are often significantly different from the exposure to which the human body is actually subjected. Therefore, a personal distributed exposimeter was developed and documented in this paper. Multiple on-body antennas are employed in order to measure the electromagnetic field strengths directly on the body. In this design, 11 commonly used frequency bands are measured, with front and back textile antennas for each of those bands. These 22 antennas are implemented in substrate-integrated-waveguide technology, thereby combining a compact size with a large bandwidth. The measurement system operates autonomously, through measurement, control and data-logging circuitry directly integrated onto the antennas. The textile-antenna based nodes are unobtrusively integrated into a garment, resulting in maximum comfort for the user. A measurement campaign using the system is currently underway in a number of European countries, yielding a large amount of valuable and unique data for epidemiological analyses.