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

Abstract

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.

A Dual-Band Wearable Exposure Meter for Personal RF Exposure Assessment in Indoor Environments: On-body Calibration in a Reverberation Chamber

“…The nodes have been calibrated on a 28-year old male subject with a body mass index (BMI) of 23.6 kg/m 2 in an RC. The on-body location of the nodes is predefined and has been studied in [8] (see Figure 1). The design of the antennas is based on [10].…”

“…It can be concluded: 1) the designed DPDE is less affected by the wearer's body compared to single nodes on the body. 2) The optimized location of the nodes for the DPDE (based on calibration in the anechoic chamber) [8] can be used in diffuse fields as well. Figure 6 depicts the mean on-body AA in diffuse fields for the optimized locations of the nodes for WiFi-2G and LTE 2600 (JN and BT).…”

“…Table 1 lists the measured S inc for WiFi-2G in the office environment using DPDE and the spectrum analyzer. The AA values for calibration of the DPDE in the anechoic chamber (AA AN ) [8] and in the RC (AA RC ) are used to obtain the actual incident power density on-body. The actual S inc should be in between both estimates but its exact value cannot be calculated, since the contribution of specular and diffuse fields in real environments is not known.…”

“…A review of factors contributing to uncertainty of PEMs can be found in [6]. Personal distributed exposure meters (PDEs), including single band [7] or multi-band nodes [8] have been proposed and calibrated on body in anechoic environments. PDEs have an smaller uncertainty compared to PEMs in specular conditions [7,8].…”

“…Personal distributed exposure meters (PDEs), including single band [7] or multi-band nodes [8] have been proposed and calibrated on body in anechoic environments. PDEs have an smaller uncertainty compared to PEMs in specular conditions [7,8]. However, it is unsure whether this is the case in diffuse RF exposure conditions (i.e.…”