Spatial Peak SAR Research Articles

Проблематика увеличения пропускной способности каналов мобильной связи и возможные пути решения

In this paper the problem of the growing demand for increasing the capacity of communication channels is considered, using the example of real statistical data of the current mobile operator, and the search for possible ways to solve this issue. The analysis of the distribution of electromagnetic fields and SAR for a three-layer model of the human head when interacting with a cell phone is carried out. The results obtained allow us to conclude that it is impossible to significantly increase the capacity of mobile terminals. The increase in power is accompanied by a significant increase in the spatial peak SAR, which exceeds the value recommended by international standards. As an alternative, the main directions and developments for raising the energy potential in the fifth generation 5G cellular radio channels in the millimeter wavelength range have been identified.

Quantitative Relationship between Whole Body Averaged SARs and Voxel SARs in Numerical Human Models of Pregnant Woman and 3‐Year‐Child for Far‐Field Exposure

SUMMARYSafety standards and guidelines for radio‐frequency exposure are being set based on whole‐body averaged SARs (WBA‐SARs) and localized average SARs. In Japan, the WBA‐SAR and 1 g localized average SAR are set at 0.4 W/kg and at 8 W/kg, respectively, except for the arms and legs and surface of body. The safety limits of WBA‐SARs were determined from observing the behavior destruction of animals for radio‐frequency exposure, but those of localized average SARs were determined under the assumption that a spatial peak SAR value does not exceed 20‐fold WBA‐SARs without their biological evidences. In this paper, to confirm whether or not the above assumption is valid, we calculated WBA‐SARs and voxel SARs in the frequency range from 50 MHz to 2 GHz in anatomical‐based human numerical models for pregnant woman and 3‐year‐child for vertically and horizontally polarized far‐field exposures, and derived the histogram and cumulative relative frequency of voxel SARs to obtain the quantitative relationship between WBA‐SARs and voxel SARs. As a result, we found that 99.90‐percentile voxel SARs are not exceeding 20‐fold WBA‐SARs, while 99.00‐percentile voxel SARs are smaller than 10‐fold WBA‐SARs in both human models.

Quantitative Relationship between Whole Body Averaged SARs and Voxel SARs in Numerical Human Models of Pregnant Woman and 3-years Child for Far-Field Exposure

Safety standards and guidelines for radio-frequency exposure are being set based on whole-body averaged SARs (WBA-SARs) and localized average SARs. In Japan, the WBA-SAR and 1g localized average SAR are set at 0.4W/kg and at 8W/kg, respectively, except for the arms and legs and surface of body. The safety limits of WBA-SARs were determined from observing the behavior destruction of animals for radio-frequency exposure, but those of localized average SARs were determined under the assumption that a spatial peak SAR value does not exceed 20-fold WBA-SARs without their biological evidences. In this paper, to confirm whether or not the above assumption is valid, we calculated WBA-SARs and voxel SARs in the frequency range from 50MHz to 2GHz in anatomical-based human numerical models for pregnant woman and 3-years child for vertically and horizontally polarized far-field exposures, and derived the histogram and cumulative relative frequency of voxel SARs to obtain the quantitative relationship between WBA-SARs and voxel SARs. As a result, we found that 99.90-percentile voxel SARs are not exceeding 20-fold WBA-SARs, while 99.00-percentile voxel SARs are smaller than 10-fold WBA-SARs in both human models.

Estimation of specific absorption rate and temperature increases in the human head due to portable telephones

The bioheat equation is solved for an anatomically based model of the human head with a resolution of 2.5 × 2.5 × 2.5 mm to study the thermal implications of exposure to electromagnetic (EM) fields typical of cellular telephones at 900 MHz.Attention has first been posed on a particular phone model, and a comparison between the absorbed power distribution and steady-state temperature increases has been carried out. The antenna output power was set to be consistent with the portable telephones of 600 mW, maximum SAR values, averaged over 1 gm, from 2.1 to 3.6 W/kg depending on the considered phone. The maximum temperature increases are obtained in the ear and vary from 0.22°C to 0.39°C, while the maximum temperature increases in the brain lie from 0.07°C to 0.17°C. These steady-state temperature increases are obtained after about 48 min of exposure, with a time constant of approximately 6 min. Application of the ANSI/IEEE safety guidelines restricting the 1 gm averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain from 0.07°C to 0.15°C at 900 MHz. Finally, considerations about the exposure limits in the considered studied frequency are made. Key words: Electromagnetic wave polarization, electromagnetic heating, finite-difference time-domain method, mobile phone, specific absorption rate, temperature increase.

Effect of low frequency modulated microwave exposure on human EEG: Individual sensitivity

The aim of this study was to evaluate the effect of modulated microwave exposure on human EEG of individual subjects. The experiments were carried out on four different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 7 Hz (first group, 19 subjects), 14 and 21 Hz (second group, 13 subjects), 40 and 70 Hz (third group, 15 subjects), 217 and 1000 Hz (fourth group, 19 subjects) frequencies was applied. The field power density at the scalp was 0.16 mW/cm(2). The calculated spatial peak SAR averaged over 1 g was 0.303 W/kg. Ten cycles of the exposure (1 min off and 1 min on) at fixed modulation frequencies were applied. All subjects completed the experimental protocols with exposure and sham. The exposed and sham-exposed subjects were randomly assigned. A computer also randomly assigned the succession of modulation frequencies. Our results showed that microwave exposure increased the EEG energy. Relative changes in the EEG beta1 power in P3-P4 channels were selected for evaluation of individual sensitivity. The rate of subjects significantly affected is similar in all groups except for the 1000 Hz group: in first group 3 subjects (16%) at 7 Hz modulation; in second group 4 subjects (31%) at 14 Hz modulation and 3 subjects (23%) at 21 Hz modulation; in third group 3 subjects (20%) at 40 Hz and 2 subjects (13%) at 70 Hz modulation; in fourth group 3 subjects (16%) at 217 Hz and 0 subjects at 1000 Hz modulation frequency.

Distribution of RF energy emitted by mobile phones in anatomical structures of the brain

The rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in possible carcinogenic effects of radio frequency (RF). Because exposure to RF from phones is localized, if a risk exists it is likely to be greatest for tumours in regions with greatest energy absorption. The objective of the current paper was to characterize the spatial distribution of RF energy in the brain, using results of measurements made in two laboratories on 110 phones used in Europe or Japan. Most (97–99% depending on frequency) appears to be absorbed in the brain hemisphere on the side where the phone is used, mainly (50–60%) in the temporal lobe. The average relative SARSAR is the specific energy absorption rate i.e. energy absorption rate per unit mass (measured in W kg−1). is highest in the temporal lobe (6–15%, depending on frequency, of the spatial peak SAR in the most exposed region of the brain) and the cerebellum (2–10%) and decreases very rapidly with increasing depth, particularly at higher frequencies. The SAR distribution appears to be fairly similar across phone models, between older and newer phones and between phones with different antenna types and positions. Analyses of risk by location of tumour are therefore important for the interpretation of results of studies of brain tumours in relation to mobile phone use.

Effect of modulated microwave radiation on electroencephalographic rhythms and cognitive processes

This paper is a review of the studies performed on microwave effects on resting electroencephalography (EEG) and visual memory and information processing during the last ten years. Some earlier results, obtained at the Biomedical Engineering Centre of the Tallinn University of Technology are reevaluated and generalized. Microwave radiation of 450 MHz, modulated at 7, 14, 21, 40, 70, 217 and 1000 Hz was applied. The calculated spatial peak SAR, averaged over 1 g, was 0.303 W/kg. The developed new methods of EEG analysis can detect small changes in the EEG signals caused by microwave exposure. Microwave exposure causes most remarkable increase in the EEG alpha power (reported also by other authors) and smaller increase in the beta power, detected by sensitive methods. The obtained results showed that the effect of microwave radiation depends on the modulation frequency and, consequently, has non-thermal origin. Sensitivity to microwave esposure is individual, the rate of the subjects significantly affected was 13-30% for different groups. The physiological adaptation of the brain compensates and even overcompensates the effect of the microwave exposure. The results confirm that the microwave effect is not linearly related to the inte nsity of the applied field. The changes in human performance of visual memory tasks and visual information processing are small, but statistically significant (p < 0.05).

Uncertainty of the One-Gram Averaged Spatial Peak SAR in Human Head for Portable Telephones due to Average Procedures

Uncertainty of the One-Gram Averaged Spatial Peak SAR in Human Head for Portable Telephones due to Average Procedures

The dependence of EM energy absorption upon human head modeling at 900 MHz

The dependence of electromagnetic energy absorption at 900 MHz in the human head on its anatomy and its modeling are investigated for RF-sources operating in the very close proximity of the head. Different numerical head phantoms based on MRI scans of 3 different adults were used with voxel sizes down to 1 mm/sup 3/. Simulations of the absorption were performed by distinguishing the electrical properties of up to 13 tissue types. In addition simulations with modified electric parameters and reduced degrees of complexity were performed. Thus, the phantoms greatly differ from each other in terms of shape, size, and internal anatomy. The numerical results are compared with those of measurements in a multitissue phantom and 2 homogeneous phantoms of different shapes and sizes. The results demonstrate that size and shape are of minor importance, Although local SAR values depend significantly on local inhomogeneities and electric properties, the volume-averaged spatial peak SAR obtained with the homogeneous phantoms only slightly overestimates that of the worst-case exposure in the inhomogeneous phantoms.