Manufacture of an RF Magnetic Shielding Plate Having Orientation Characteristics

摘要

As one of the basic areas of research for the improvement of the electromagnetic environment, this paper has developed a carbon plate having orientation characteristics. To exhibit the orientation characteristics in a plane wave, a slit was cut on the surface of a carbon plate. The value of the radio frequency (RF) magnetic shielding degree $SD_{rm HP}$ when holding the slit in the carbon plate perpendicularly, in the frequency region from 1 MHz to 1 GHz, increased with frequency and had a value of 48 dB at 1 GHz. It was also shown that the value of $SD_{rm HH}$ when holding the slit horizontally indicated about 15 dB in the frequency region from 1 MHz to 1 GHz. Namely, the difference in the values of shielding degree of the carbon plate versus the orientation of slit indicated the characteristics of the orientation. Experimental results revealed several characteristics of the slit carbon plate that include the influences of the slit length $L$, slit number $N$, and slit width $w$ on the characteristics of the orientation. In this paper, the orientation characteristics were improved by the superposition of a slit ferrite plate over a slit carbon plate, termed the compound plate. In addition, important criteria are discussed for the design of a plate for effective RF magnetic shielding having orientation characteristics.