A numerical and experimental comparison of human head phantoms for compliance testing of mobile telephone equipment

In this work, the numerical dosimetry in human exposure to the electromagnetic fields from antennas of wireless devices, such as those of wireless local area networks (WLAN) access points or phone and computer peripherals with Bluetooth antennas, is analyzed with the objective of assessing guidelines compliance. Several geometrical configurations are considered to simulate possible exposure situations of a person to the fields from WLAN or Bluetooth antennas operating at 2400 MHz. The exposure to radiation from two sources of different frequencies when using a 1800 MHz GSM mobile phone connected via Bluetooth with a hands-free car kit is also considered. The finite-difference time-domain (FDTD) method is used to calculate electric and magnetic field values in the vicinity of the antennas and specific absorption rates (SAR) in a high-resolution model of the human head and torso, to be compared with the limits from the guidelines (reference levels and basic restrictions, respectively). Results show that the exposure levels in worst-case situations studied are lower than those obtained when analyzing the exposure to mobile phones, as could be expected because of the low power of the signals and the distance between the human and the antennas, with both field and SAR values being far below the limits established by the guidelines, even when considering the combined exposure to both a GSM and a Bluetooth antenna.

Section: Methodology and Modelsmentioning

confidence: 99%

FDTD assessment of human exposure to electromagnetic fields from WiFi and bluetooth devices in some operating situations

Martínez‐Búrdalo

Muñoz

Sanchis

et al. 2008

“…Only Schönborn et al [1998], Christ et al [2005], and Kainz et al [in press] use anatomically correct head models generated from MRI scans of children. Different source types such as dipoles, generic mobile phones with monopole and helical antennas as well as complex CAD based models of real world phones were applied.…”

Section: Introductionmentioning

confidence: 99%

Differences in RF energy absorption in the heads of adults and children

Christ

Kuster

2005

Self Cite

There has been a long and controversial debate on possible differences in electromagnetic (EM) energy absorption between adults and children during cell phone usage. Some published studies report higher specific absorption rate (SAR) in children and explain this based on smaller head size. More recently, age dependent changes of the dielectric tissue parameters have again ignited the discussion. This study intends to give a comprehensive review of the current state of knowledge about the parameters and mechanisms affecting the exposure of the mobile phone user with special focus on the exposure of children. Discussed are the absorption mechanism, tissue parameters, the effect of the pinna, and the uncertainties associated with head models based on spheroids, scaled adult heads, and magnetic resonance imaging (MRI) data of children. The conclusions of the review do not support the assumption that the energy exposure increases due to smaller heads, but identifies open issues regarding the dielectric tissue parameters and the thickness of the pinna.

“…Although only IEEE [2004] provides a relaxation of limits for pinna, it also states that this relaxation has to be considered without violating the general provisions. It is known that if the limited SAR values for the head tissue are met, the values for the pinna treated as an extremity are intrinsically met as well [Christ et al, 2005]. To minimize pinna discrepancies when performing the simulations, the BLAS model has an ear completely attached to the head, as can be observed from Figures 1 and 9, that is, we use what some works call a ''compressed'' or ''collapsed'' pinna.…”

Section: Methodsmentioning

confidence: 97%

“…The simplified EPI model is useful for algorithm validation purposes since SAR values are not directly linked to head size [Christ et al, 2005].…”

Section: Methodsmentioning

confidence: 99%

Effect of pierced metallic objects on sar distributions at 900 MHz

Fayos-Fernández

Arranz-Faz

Martinez-Gonzalez

et al. 2006

A study of the interaction between mobile phone antennas and a human head in the presence of different types of metallic objects, attached and pierced to the compressed ear, is presented in this article. Computed and measured results have been performed by considering a quasi-half-wavelength dipole as the radiating source and measurements with the DASY4 dosimetric assessment system. Two different human head models have been implemented: a homogeneously shaped sphere and a three-level head model with four different kinds of tissue. Antenna input impedance, reflection coefficient, radiation patterns, SAR distribution, absorbed power, and peak SAR values have been computed and measured for diverse scenarios, electromagnetic simulators, and organs. Despite the measuring accuracy limitations of the study, both simulated and measured results suggest that special attention has to be paid to peak SAR averaged values when wearing metallic objects close to the radiation source, since some increment of peak SAR averaged values is expected.