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In compliance assessments of radio-frequency exposure from cellular-phone-base station antennas, the root of 6-min time average of the squared electric fields is commonly required. Under the assumption that the time-varying electric fields belong to an ergodic process, a new approach has been proposed to estimate the 6-min time average from the ensemble average of the squared electric fields based on amplitude probability distribution (APD) measurements for a shorter time, much less than 6 min. The usefulness of the approach has been demonstrated at the 800-MHz band and the 1.5-GHz band, and the results have shown that by using a fast sampling rate, 1-min APD measurements could give a good estimate of the 6-min time average with an accuracy of within [+ or -] 10%. Index Terms--Amplitude probability distribution (APD), base station antenna, cellular phone, electric field intensity assessment.

For investigation of possible bio-effects of the 2-GHz wideband code division multiple access cellular system on pregnant and newborn rats, we have developed an unrestrained whole-body exposure setup, which employs two dipole antennas to induce a circularly polarized field at the location of the rats. The dosimetric results, by using the finite-difference time-domain method in conjunction with anatomical rat models, have confirmed the realization of a circular polarization in the exposure space, and have also revealed that the exposure setup can maintain a relative variation of the whole-body average specific absorption rate (SAR) within [+ or -]60% of the designed average level for various positions of rats. These findings show that the exposure setup is reasonable and acceptable in view of the actual SAR variation in a human body due to RF exposure from base stations. Index Terms--Bio-effect of electromagnetic field, circular polarization, pregnant rat, RF, whole-body exposure setup.

This paper investigates the correlation between maximum temperature increases and peak spatial-average specific absorption rates (SARs), calculated by different average schemes and masses. For evaluating the effect of mass on the correlation properly, a three-dimensional Green's function is presented. From our computational investigation, no best average mass for peak spatial-average SAR exist from the aspect of the correlation with maximum temperature increase. This is attributed to the frequency dependent penetration depth of EM waves. Maximum temperature increase in the head including the pinna is reasonably correlated with peak spatial-average SARs for most average schemes and masses considered in this paper. Maximum temperature increase in the head only (excluding the pinna) is reasonably correlated with peak 10-g SARs for the average schemes considered in this paper. The rationale for this result is explained using the Green's function. The point to be stressed here is that the slope correlating them is largely dependent on the average scheme and mass. Additionally, good agreement is observed in the slopes obtained by using two head models, which have been developed at Osaka University and Nagoya Institute of Technology. However, weak correlation is observed for the brain, which is caused by the difference of the positions where peak SAR and maximum temperature increase appear. The 95th percentile values of the slope correlating maximum temperature increases in the head or brain and peak spatial-average SAR are quantified for different average schemes and masses. Index Terms--Bio-heat transfer equation, human exposures, specific absorption rate (SAR), temperature increase.

In designing an in vivo near-field exposure setup for testing biological effects of cellular phones, one generally uses a small still animal because a plastic holder is used to restrain it. One also takes no account of the exposure box with radio wave absorbers as well as the plastic holder. In this paper, for the in vivo exposure setup developed in the National Institute of Information and Communications Technology (NICT), which was used for testing the promoting effect of 1.439- and 1.95-GHz digital cellular phones on rat brain carcinogenesis, we investigated the effects of the above-mentioned factors on the dosimetry design using the finite-difference time-domain (FDTD) method in conjunction with an anatomical rat model. As a result, we found that the specific absorption rate (SAR) averaged in the brain was 18% higher at maximum than the previously designed level due to the existence of the exposure box and the plastic holder and that the variation due to the rotation of the rat's head inside the plastic holder was within 10%. The backward movement of the rat along the plastic holder was more serious, which yielded a decrease of nearly 20% for the average SAR in the brain. Index Terms--Cellular phone, in vivo exposure setup, specific absorption rate (SAR), uncertainty evaluation.

The specific absorption rates (SAR) determined computationally in the specific anthropomorphic mannequin (SAM) and anatomically correct models of the human head when exposed to a mobile phone model are compared as part of a study organized by IEEE Standards Coordinating Committee 34, SubCommittee 2, and Working Group 2, and carried out by an international task force comprising 14 government, academic, and industrial research institutions. The detailed study protocol defined the computational head and mobile phone models. The participants used different finite-difference time-domain software and independently positioned the mobile phone and head models in accordance with the protocol. The results show that when the pinna SAR is calculated separately from the head SAR, SAM produced a higher SAR in the head than the anatomically correct head models. Also the larger (adult) head produced a statistically significant higher peak SAR for both the 1- and 10-g averages than did the smaller (child) head for all conditions of frequency and position. Index Terms--FDTD methods, IEEE standards, phantom, simulation, software standards, specific absorption rate (SAR), specific anthropomorphic mannequin (SAM).

In electromagnetic dosimetry of children heads for mobile telephones, the dielectric properties of biological tissues for adults are so far being used due to the lack of the ones of children. In this paper, we derived an empirical formula according to Lichtenecker's exponential law for the complex permittivity of various tissues as a function of the hydrated rate or the total body water (TBW). We first examined its validity using the data measured by Peyman et al. for rats, and then applied the formula to the dielectric properties of 7-year-old and 3-year-old child head models by means of the relationship between the TBW and the age. With the dielectric properties for children derived in such an approach, we analyzed numerically the spatial peak specific absorption rate (SAR) for a 900-MHz mobile telephone in adult and child head models. As a result, we found that the dielectric properties for children do not affect significantly the 1- or 10- g averaged spatial peak SAR as well as the penetration depth. The finding could be qualitatively explained as cancellation of the increased conductivity and decreased electric field penetrating into the tissue because of the same degree of increase between the conductivity and permittivity in children compared to adults. Even in an extreme case, the age effect on the spatial peak SAR of dielectric properties is still within 10%. Index Terms--Children, dielectric property, FDTD method, mobile telephone, penetration depth, specific absorption rate.

This paper investigates the correlation between the peak specific absorption rate (SAR) and the maximum temperature increase in head models of adults and children due to a dipole antenna. Much attention is paid to the effect of variation of electrical and thermal constants on the correlation for the child models, since these constants of child tissues are different from those of adult tissues. For investigating these correlations thoroughly, a total of 1400 situations are considered for the following six models: 3-year-old child, 7-year-old child, and adult models developed at the Nagoya Institute of Technology and the Osaka the University. The numerical results are analyzed on the basis of statistics. We find that the maximum temperature increases in the head can be estimated linearly in terms of peak SAR averaged over 1- or 10-g of tissue. In particular, no clear difference is observed between the adult and child models in terms of the slopes correlating the maximum temperature increase with the peak SAR. Also, the effect of electrical and thermal constants of tissue on these correlation is found to be marginal. Further, we discuss possible maximum temperature increases in the head and brain for SAR limits prescribed in safety guidelines. For the adult model developed at the Osaka Univ., these are found to be 0.26 [degrees]C and 0.10 [degrees]C at the SAR value of 1.6 W/kg for 1-g cubic tissue and 0.59 [degrees]C and 0.21 [degrees]C at the SAR value of 2.0 W/kg for 10-g cubic tissue. Similarly, for the 3-year-old child model at Osaka Univ., these are 0.23 [degrees]C and 0.11 [degrees]C for the value of 1-g SAR and 0.53 [degrees]C and 0.20 [degrees]C for the value of 10-g SAR. Index Terms--Bioheat equation, dipole antenna, dosimetry, specific absorption rate (SAR), temperature increase.

In this paper, high-frequency (HF) and microwave electromagnetic (EM) fields in experimental fusion facilities were statistically measured, and the exposure levels were compared with safety guidelines to ensure workers' safety. Since leaked EM fields have time-varying characteristics whose amplitudes vary according to a stochastic process, a measurement of their amplitude probability distribution (APD) was conducted. An approach was then presented to derive from the measured APD the specific absorption rate (SAR) in an exposed human body. The statistically-averaged whole-body-averaged SAR showed that the leaked field intensities were low enough to not cause any thermal hazards for the workers in the specific EM environment. The statistically averaged SAR also showed fair agreement with the SAR derived from the time average over 6 min as specified in the safety guidelines. This finding suggests the usefulness of the APD measurement in lieu of a field measurement over a 6-min period because the APD can be obtained in a time period much less than 6 min. Index Terms--Amplitude probability distribution (APD), electromagnetic environment, experimental fusion facilities, field leakage, human exposure, statistically averaged specific absorption rate (SAR).

In most in vivo exposure setups for testing biological effects of cellular telephones on a small animal, a plastic holder is commonly used for restraining the small animal in order to keep a constant near-field exposure. Although the plastic holder should affect the specific absorption rate (SAR) in the small animal, few researchers have considered its influence in their exposure setup design or dosimetry evaluation. We previously developed an in vivo exposure setup for testing the promoting effect of digital cellular telephones on mouse skin carcinogenesis. In this paper, the influence of a plastic holder for restraining the mouse in the exposure setup was investigated numerically and experimentally. The numerical investigation was conducted by using the finite-difference time-domain (FDTD) method together with a realistically shaped mouse model. The validity of the FDTD modeling was verified by the antenna impedance measurement. As a result, an increase of 18% on the peak SAR was found due to the presence of the mouse holder. Index Terms--Biological effect, cellular telephone, in vivo exposure setup, plastic holder, specific absorption rate.

The controversy on the dosimetry in children's heads for mobile telephones is still inconsistent. Gandhi's group reported a considerable increase of the spatial peak specific absorption rate (SAR) in children's heads, while Kuster's group claimed that there was not a significant difference in the SAR between children and adults. In this paper, based on Japanese children's statistical data on external shapes of heads, we newly developed two kinds of children's models from a Japanese adult head model. Using the children's head models, we calculated the local peak SAR under the same conditions as those previously employed by Gandhi's and Kuster's groups. Compared to the local peak SAR in the adult head model, we found a considerable increase in the children's heads when we fixed the output power of the monopole-type antenna, but no significant differences when we fixed the effective current of the dipole-type antenna. This finding suggests that the contradictory conclusions drawn by the above two groups may be due to the different conditions in their numerical peak SAR calculations. Index Terms--Children, dosimetry, mobile telephone, specific absorption rate (SAR).

Temperature rises in the human head for portable telephones were computed with an anatomically based head model at 900 MHz and 1.5 GHz. The specific absorption rate (SAR) in the human head was determined using the finite-difference time-domain (FDTD) method, while a bioheat equation was numerically solved also using the FDTD method. The portable telephone was modeled by a quarter-wavelength monopole antenna on a dielectric covered metal box. The source geometries considered were the telephone barely touching the ear and the telephone pressing the ear, both having a vertical alignment at the side of the head. The antenna output power was set to be consistent with the portable telephones of today: 0.6 W at 900 MHz and 0.27 W at 1.5 GHz. Computed results show that a phone time of 6-7 min yields a temperature rise of approximately 90% of the steady-state value. Application of the ANSI/IEEE safety guidelines restricting the 1-g-averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain of 0.06 [degrees] C, and application of the ICNIRP/Japan safety guidelines restricting the 10-g-averaged spatial peak SAR to 2 W/kg results in the maximum temperature rise in the brain of 0.11 [degrees] C, both at 900 MHz and 1.5 GHz.

A prediction of the electromagnetic interference (EMI) of pacemakers due to mobile phones is significant in improving the immunity of pacemakers. The Pacemaker Committee of Japan recently conducted immunity tests of pacemakers for mobile phones, and consequently concluded that the connector between the pacemaker housing and the lead wire of the electrode plays a major role for the EMI due to mobile phones. Based on this finding, a computer model for predicting the EMI level has been presented, in which the internal impedance seen from the connector was considered as a load, and the metal portions consisting of the pacemaker housing and the lead wire of the electrode were considered as two elements of a receiving antenna. Interference voltages induced through the connector were analyzed by using the finite-difference time-domain method in conjunction with a torso and mobile phone model. The modeling was validated by comparison with previously reported experimental results. Index Terms--Electromagnetic interference, FDTD analysis, implanted pacemaker, mobile telephone.