10-g Averaged Specific Absorption Rate Research Articles

Threshold Power of Canonical Antennas for Inducing SAR at Compliance Limits in the 300–3000 MHz Frequency Range

A study of the specific absorption rate (SAR) in an exposed body induced by canonical antennas is presented, with the aim of determining an upper bound for the antenna transmit power that demonstrates that a product is inherently compliant with internationally accepted radio frequency (RF) exposure limits. Starting from the fundamental limits in antenna quality factor (Q) and the corresponding bandwidth, several antenna sizes are selected, and their SAR distributions are computed using the method of moments (MoM) and finite-difference time domain (FDTD) method in the frequency range 300-3000 MHz. The threshold powers are then determined, below which the peak 1-g and 10-g averaged SAR would not exceed the limits specified in international exposure standards. From the data, simple expressions are derived to estimate the threshold power over a wide range of antenna sizes, frequencies, and distances from the body. It is demonstrated that the results presented in this paper are conservative in comparison with the measured SAR data of real products as well as other published data

Simple Modeling of an Abdomen of Pregnant Women and Its Application to SAR Estimation

This paper presents a simple abdomen model of pregnant women and the evaluation of the specific absorption rate (SAR) inside the proposed model close to normal mode helical antennas (NHAs), which are replacing the portable radio terminals for business at 150MHz. First, dielectric properties of amniotic fluid and those of fetus of rabbit, which have about the same electrical properties as human, are measured. As a result, the conductivity of amniotic fluid is 1.8 times and that of fetus is 1.3 times higher than that of adult muscle at 150MHz. The result also suggests the modeling of pregnant women including the amniotic fluid and the fetus is necessary. Next, a simple abdomen model of pregnant women based on the measurements of magnetic resonance (MR) images of Japanese women in the late period of pregnancy is proposed. Finally, the SAR inside the proposed abdomen model close to 0.11λ and 0.18λ NHAs is calculated using the finite-difference time-domain (FDTD) method. As a result, we have confirmed that the 10-g average SAR in the fetus is sufficiently less than 2 W/kg, when the output power of NHAs is 5 W, which is the maximum nower of portable radio terminals in Japan.

Faster Determination of Mass-Averaged SAR From 2-D Area Scans

An algorithm is presented that accurately and quickly estimates the peak 1or 10-g averaged specific absorption rate (SAR) in a human phantom when exposed to a wireless device. Instead of performing both an area scan and a zoom scan (as per international standards), only the area scan and knowledge of the transmit frequency are needed. The accuracy of the algorithm has been demonstrated across a broad frequency range (150-2450 MHz) and for both 1- and 10-g averaged SAR using a sample of 264 SAR measurements from 55 wireless handsets. For the sample size studied, the root-mean-squared errors of the algorithm are 1.2% and 5.8% for 1- and 10-g averaged SAR, respectively. It is shown that the algorithm works well in both head and body phantoms.

Simple Evaluation Method of Estimating Local Average SAR

Generally, the E-field probe method and the thermographic method are used for the measurement of the specific absorption rate (SAR). However, the thermographic method is not efficient to measure the local average SAR. Therefore, in this paper, the simple evaluation method of estimating local average SAR using the SAR distribution on specific planes and axes has been proposed. First, the limit of simplification has been investigated when four types of antennas, which are a half-wave dipole antenna, monopole antenna mounted on a metal box, planar inverted F antenna, and a half-wave dipole antenna with a planar reflector, are close to the COST244 cubical and spherical head model. Next, the effect of the distance and the frequency on the average SAR using the proposed method has been evaluated. Finally, the local average SAR in the realistic head model using the distribution of the specific plane and axes has been investigated. From these investigations, the agreement between the local 10-g average SAR calculated by the data in the optimum plane or axes and that in the three dimensions is within /spl plusmn/10% in almost all cases.

Computation With a Parallel FDTD System of Human-Body Effect on Electromagnetic Absorption for Portable Telephones

Using our recently implemented parallel finite-difference time-domain computation system on Linux-based personal computers, we investigated the human-body effect on the peak specific absorption rate (SAR) in the human head for portable telephones. Taking into account the whole human body, we found that there was a difference within 5.3% for the 1- and 10-g averaged spatial peak SARs and a difference within 19% for the SAR in the brain and eyes compared to the isolated head model. Moreover, in most realistic-use positions, we found that the SAR was slightly decreased due to the body effect. These results further support the rationale of using an isolated human-head model in the SAR evaluation for portable telephones.