RF Magnetic Shielding Effects of a Bincho-Charcoal Plate

Abstract

Recently, there has been increased interest for electromagnetic shielding in the radio frequency (RF) region. The use of effective electromagnetic shields has, moreover, been required to improve the electromagnetic environment. The present paper has applied bincho-charcoal, a high quality charcoal found in Japan, to improve RF electromagnetic shields. Bincho-charcoal makes an excellent shield, due to a very large value of relative permittivity in the RF region. In the present research, the evaluation of the RF magnetic shielding degree SD_H of the bincho-charcoal was limited to a plate being exposed to an electromagnetic wave. The SD_H of the single plate was found to increase with an increase in RF frequency over the range from 1 MHz to 1 GHz. The value of SD_H at 100 MHz was found to be about 15 dB. The present authors have, furthermore, improved the value of SD_H by the use of a triple plate, constructed from three bincho-charcoal plates. The SD_H of the triple plate at 100 MHz was found to be improved by about 15 dB over that of the single plate. In addition, the SD_H was shown to be improved by the superposition of a copper plate over the triple plate.