Sang-Il Kwak

Hybrid model for the personal exposure meter response in an outdoor environment

When a personal exposure meter (PEM) is worn by a human subject, the electric-field strength measured at the PEM is affected by a body shadowing effect. In our study, a hybrid model is proposed for modeling the body shadowing effect for when the PEM is used in an outdoor environment. The hybrid model contains responses to direct and diffused waves, the factors related to the transmission path and cross-polarization discrimination, respectively. To derive the hybrid model, responses for the direct and diffused waves are measured using a human phantom in an anechoic chamber and a reverberation chamber, respectively. Responses are measured at multiple locations in an outdoor environment and compared to the responses of the hybrid model. The hybrid model response has quartiles that deviate by an average of only 2.2u2009dB (1.29) from the same quartiles of the outdoor responses. Such quartile deviations are significantly smaller than those of the previous model with a body shadowing effect. Bioelectromagnetics. 38:626-647, 2017.

Design and Analysis of Novel Broadband EM Wave Absorbers Based on Lossy EBG Surface

The design method and analysis of novel broadband electromagnetic (EM) wave absorbers is presented in this paper. The proposed absorber is a planar structure based on lossy Electromagnetic Bandgap (EBG) surface with the specific sheet resistance, which replaces conventional resistive layer of Salisbury screen. The absorber performance can be easily controlled by simply modifying the EBG surface. The analysis for the reflectivity response due to the phase variation of the reflection and transmission recognizes electrical characteristics of the proposed absorber. A broadband reflectivity response with about 96% fractional bandwidth below -10 dB is presented. The computational results are presented to verify the functioning of the proposed absorber.

Development of multi-band personal dosimeter for RF and ELF exposure monitoring

This paper presents development of a multi-band dosimeter to detect exposure to a radio frequency electric field (RF-EF) and an extremely low-frequency magnetic field (ELF-MF). For the RF-EF detection, an infinitesimal dipole antenna is designed to achieve the dosimeter operation of a wide bandwidth. A signal amplifier is integrated into the antenna, so the dosimeter has a high sensitivity level. When a human subject wears the dosimeter, the human body of the subject attenuates the signal received through the antenna. The signal attenuation caused by the human body is investigated by measurement. For the ELF-MF detection, a signal processing module including induction coils is designed. When an ELF-MF induces a signal at the induction coil, the processing module processes the induced signal using a fast Fourier transform (FFT) technique. The processing module is equipped with signal channels for RF-EFs to process the signal received through the dipole antenna; hence, the exposure detection is possible at the multi-band of RF and ELF. The developed technologies can be effectively applied to realize the multifunctional dosimeter that provides useful data for exposure assessment.

Effect of air-gap between metal strips and a ferrite plate on magnetic shielding

In this paper, the effect of air-gap between the metal strip and ferrite plate on magnetic shielding in the presence of a periodic line current source is analyzed in two-dimensional and approximate model of the WPT coils in electric vehicles and mobile devices. An analytical method based on Fourier transform and mode matching technique is proposed to investigate the penetration of quasistatic magnetic field into the ferrite plate and metal strips.

Design of a novel broadband microwave absorber using a EBG structure

A novel broadband microwave absorber based on a lossy Electromagnetic Bandgap (EBG) structure is presented, and the absorption performance is examined. The proposed absorber includes a lossy EBG surface with the specific sheet resistance, which replaces the conventional resistive sheet of Salisbury screen. The measured result for the absorber showing a broadband reflectivity response with about 76% fractional bandwidth below −10 dB is presented, and a new structure with more enhanced absorption characteristic and other computational results to confirm the functioning of the absorber are presented. The measured and simulated results for the proposed absorber are in good agreement.