Seon-Eui Hong

SAR Comparison of SAM Phantom and Anatomical Head Models for a Typical Bar-Type Phone Model

The current IEEE 1528 and IEC 62209-1 standards specify a simplified physical model of the human head to provide conservative measurement procedures of the peak spatial-average specific absorption rate (SAR) of a mobile phone. This means that the evaluated SAR in a specific anthropomorphic mannequin (SAM) head model should be higher than in the heads of a significant majority of users under normal operational conditions. In this paper, the conservativeness of the SAM is investigated by numerically comparing the SAR in the SAM with those in four anatomical head models at different ages for exposure from a typical bar-type mobile phone. A numerical bar-type phone model with an internal antenna at the bottom of the phone body was implemented at 835 and 1850 MHz. This model provides an SAR pattern and levels similar with the commercial bar phones released in Korea. For two standard test positions, spatial peak 1- and 10-g SARs were calculated for both the SAM phantom and anatomical head models. The SARs were also calculated when the antenna is located on top of the phone. The results show that the SAM phantom provides a conservative evaluation for a phone model with the antenna on the top. However, when the antenna is located at the bottom, the hotspot in the SAM occurred farther from the antenna feed point, and, thus, produced lower 1- and 10-g SAR results compared with the anatomical models.

Numerical Implementation of Representative Mobile Phone Models for Epidemiological Studies

This paper describes an implementation method and the results of numerical mobile phone models representing real phone models that have been released on the Korean market since 2002. The aim is to estimate the electromagnetic absorption in the human brain for casecontrol studies to investigate health risks related to mobile phone use. Specific absorption rate (SAR) compliance test reports about commercial phone models were collected and classified in terms of elements such as the external body shape, the antenna, and the frequency band. The design criteria of a numerical phone model representing each type of phone group are as follows. The outer dimensions of the phone body are equal to the average dimensions of all commercial models with the same shape. The distance and direction of the maximum SAR from the earpiece and the area above –3 dB of the maximum SAR are fitted to achieve the average obtained by measuring the SAR distributions of the corresponding commercial models in a flat phantom. Spatial peak 1-g SAR values in the cheek and tilt positions against the specific anthropomorphic mannequin phantom agree with average data on all of the same type of commercial models. Second criterion was applied to only a few types of models because not many commercial models were available. The results show that, with the exception of one model, the implemented numerical phone models meet criteria within 30%.

Numerical anlaysis of human exposure to electromagnetic fields from wireless power transfer systems

In this paper, we investigate a human exposure to wireless power transfer system operating at 1.8 MHz and 6.78 MHz. A method comprising a finite element method and a finite difference time domain is used for the numerical analysis of human exposure. The SARs of the Korean human body model are evaluated in relation to the different positions and orientation of wireless power transfer system. We discuss the numerical computation results along with the Non-Ionizing Radiation Protection (ICNIRP) guideline.

Mobile phone types and SAR characteristics of the human brain

Mobile phones differ in terms of their operating frequency, outer shape, and form and location of the antennae, all of which affect the spatial distributions of their electromagnetic field and the level of electromagnetic absorption in the human head or brain. For this paper, the specific absorption rate (SAR) was calculated for four anatomical head models at different ages using 11 numerical phone models of different shapes and antenna configurations. The 11 models represent phone types accounting for around 86% of the approximately 1400 commercial phone models released into the Korean market since 2002. Seven of the phone models selected have an internal dual-band antenna, and the remaining four possess an external antenna. Each model was intended to generate an average absorption level equivalent to that of the same type of commercial phone model operating at the maximum available output power. The 1 g peak spatial SAR and ipsilateral and contralateral brain-averaged SARs were reported for all 11 phone models. The effects of the phone type, phone position, operating frequency, and age of head models on the brain SAR were comprehensively determined.

Evaluation Method of Electromagnetic Field Exposure Levels from Wireless Power Transfer System

—If the wireless power transfer system is located to a person; the magnetic fields produce by the wireless power transfer system will vary in the region occupied by the human body. According the Institute of Electrical and Electronic Engineers (IEEE) and International Commission on Non-Ionizing Radiation Protection (ICNIRP), the predicated or the measured values have to be spatially averaged in an area representing the dimension of the human body and compared with the adopted reference level of exposure. Although spatial averaging is better approximation compared to point measurement, the standard of how to perform such an assessment does not exist. This paper describes the method for spatial averaging magnetic field. We analyzed the difference of spatial averaging value (1-and 2-dimensional templates consists of different number of position) and compared it with the standard uncertainty for measurement drift. The proposed methods are given to present the effectiveness of the choice of measurement position.

Evaluation of SARs in a human-body model due to smart-watch wearable device

In this study, we investigate the SAR of the smart-watch wearable device with a planar inverted F antenna. Currently, the standards for compliance testing of limb-worn devices specifics the use of a flat phantom to provide conservative estimates of SAR. This means that SAR estimated by using a flat phantom should be higher than the SAR in real exposure scenario. In order to verify this, SARs for standard flat phantoms are calculated and compared with those calculated for anatomical human-body models. The smart-watch model produce higher SARs in human-body models than in flat phantom. We determine the different phantom dimension, shape, and tissue structure are the reason for difference in spatial peak SAR results between human-body model and flat phantom.

Mobi-Kids Study: Exposure Assessment of Electromagnetic Radiation from Mobile Phones -II. Evaluation Method of Head SAR and Cumulative Dose

SAR calculation method following the Mobi-Kids study protocol is analyzed and evaluation method of cumulative RF dose from mobile phones which have been used by a subject of case and control groups is proposed. An SAR database is built by calculating SAR distributions in 4 head models at different ages for representative phone models with the same conducted power. To obtain SAR distribution in a subject’s head for a specific commercial phone which had/have been used by him/her, an SAR correction factor using SAR compliance test results is determined. Cumulative dose is calculated by considering mobile phone characteristics and use pattern such as call time and laterality(right and left).

A study SARs for smart-watch model with monopole antenna

Currently, the standard and regulations for specific absorption rate (SAR) testing of limb-worn devices specify the use of the flat phantom and the users wrist is not considered. In this paper, the SARs for standard flat phantoms are calculated and compared with body shape phantom and anatomical human-body model. And we investigate the effect of wrist model during the SAR evaluation.

Numerical compliance testing of human exposure to electromagnetic radiation from smart-watches

In this study, we investigated the electromagnetic dosimetry for smart-watches. At present, the standard for compliance testing of body-mounted and handheld devices specifies the use of a flat phantom to provide conservative estimates of the peak spatial-averaged specific absorption rate (SAR). This means that the estimated SAR using a flat phantom should be higher than the SAR in the exposure part of an anatomical human-body model. To verify this, we numerically calculated the SAR for a flat phantom and compared it with the numerical calculation of the SAR for four anatomical human-body models of different ages. The numerical analysis was performed using the finite difference time domain method (FDTD). The smart-watch models were used in the three antennas: the shorted planar inverted-F antenna (PIFA), loop antenna, and monopole antenna. Numerical smart-watch models were implemented for cellular commutation and wireless local-area network operation at 835, 1850, and 2450 MHz. The peak spatial-averaged SARs of the smart-watch models are calculated for the flat phantom and anatomical human-body model for the wrist-worn and next to mouth positions. The results show that the flat phantom does not provide a consistent conservative SAR estimate. We concluded that the difference in the SAR results between an anatomical human-body model and a flat phantom can be attributed to the different phantom shapes and tissue structures.

Preamplifier for fiber-optic Millimeter wave Wireless LAN

A preamplifier for fiber-optic millimeter-wave wireless system is presented based on a fully stabilized 0.12 mum PHEMT technology and is realized in a LTCC technology. The preamplifier is designed with parallel feedback and is minimized using inter-stage and T-section matching for chip size. The preamplifier module, in corporation of three amplifying stages, is used in microstrip line type, and shows measured transimpedance gain of 59 dBOmega. and return loss of less than -5 dB with a 1 dBOmega. ripple around the center frequency.