CONDUCTED NOISE SUPPRESSION IN GHZ RANGE BY COMPOSITE SHEETS AND FERRITE-PLATED FILMS

摘要

We measured transmission loss ΔP_(loss) and reflection coefficient S_(11) of microstrip line circuit induced by commercialized composite-sheets, in which Fe-Si-Al flakes were dispersed in polyurethane resin, up to 10 GHz. The composite-sheets 300 μm in thickness exhibited a large transmission loss ΔP_(loss) of 70% at 3 GHz, which, however, decreased down to 15% as the thickness was reduced to 25 μm. To attain stronger noise suppression, we fabricated, using Ni-Zn ferrite films synthesized from an aqueous solution, novel ferrite-film noise suppressors of two types. In the "sheet type," Ni-Zn ferrite film was deposited on polyimide sheet. In the "direct-deposition-type," Ni-Zn ferrite film was deposited directly on to the microstrip line fabricated on the printed circuit board. ΔP_(loss) per thickness for ferrite-film noise suppressor of sheet type and direct-deposition type was 16 and 20 times larger than that for the composite-sheet at 5 GHz, respectively. Both types of ferrite-film noise suppressors exhibited S_(11) low enough (< -10 dB) to be applied as conducted noise suppressors up to 10 GHz.