Orientation Characteristics in RF Magnetic Shielding Effects of BPSCCO Plates

Abstract

As one of the basic areas of research for improvement of the electromagnetic environment by use of a bulk high-critical temperature superconductor, the present paper has examined a Bi-Pb-Sr-Ca-Cu-O (BPSCCO) plate with a slit, which displays orientation characteristics in the RF magnetic shielding. According to the results, the value of the RF magnetic shielding degree HP , when orienting the slit of the BPSCCO plate perpendicular to the ground, increased in the frequency region of 1 MHz (20 dB) to 30 MHz (40 dB), and then reminded approximately constant in the region of 30 MHz to 3 GHz (40 dB). The value of the RF magnetic shielding degree HH when orienting the slit horizontally indicated an average value of 15 dB in the region of 1 MHz to 3 GHz. Namely, the difference in the RF magnetic shielding degree, HP HH , as related to the direction of the slit represents orientation characteristics. Experimental results revealed several characteristics of the slit BPSCCO plate that include the dependencies of the orientation characteristics on the slit length, slit width, and slit number.

Improved Frequency Properties of the Orientation Characteristics of a Slit Carbon Plate in an RF Magnetic Field: The Sandwich Structure of Two Slit Ferrite Plates on a Slit Carbon Plate

“…In Table 1, the length L, width w, and slit number N are listed for the optimum size of the slit plates for displaying the maximum orientation characteristics in RF magnetic shielding effects, as reported in Refs. [3,4]. It has been reported that the orientation characteristics for the slit ferrite plate are opposite to those for the slit carbon plate, in association with the value of characteristic impedance Z S (>Z 0 (=120π Ω), characteristic impedance of free space) for ferrite [3,4].…”

“…In the present research, use was made of commercial carbon (Toyo-Tanso, IG-110, 50 mm square, thickness of 1 mm) and ferrite (TDK, IB-015, 50 mm square, thickness of 2 mm) plates. Slits were cut in the surface of the carbon and ferrite plates by the use of a diamond saw, operated at a low cutting rate to prevent any influence of heat and cracking [4]. All slits were made through the entire thickness of the plates.…”

“…[3,4]. It has been reported that the orientation characteristics for the slit ferrite plate are opposite to those for the slit carbon plate, in association with the value of characteristic impedance Z S (>Z 0 (=120π Ω), characteristic impedance of free space) for ferrite [3,4]. Therefore, when the slit sandwich plates are constructed, the slit directions of the slit ferrite plates are arranged to perpendicularly intersect those of the slit carbon plate.…”

“…The two metal cells for forming plane wave have the same shape and size as those reported in Refs. [4,6]. The output of the receiving antenna is amplified by 38 dB using a preamplifier (Sonoma, 317), and guided to the input terminal of the spectrum analyzer.…”

“…Optimum sizes of the slit plates for maximum orientation characteristics in RF magnetic shielding effects[3,4]. Here, L, w, and N represent the length, width, and number of slits, respectively.…”