2003 Volume 3 Issue 4 Pages 129-132
Two types of conducted noise suppressors usable in a GHz range were fabricated using Ni-Zn ferrite films deposited from aqueous solutions. One is a direct-deposition type, in which Ni-Zn ferrite films are deposited directly on a microstrip line on an epoxy printed circuit board (PCB). The other is a sheet-type, in which the surfaces of Ni-Zn ferrite films deposited onto the polyimide sheet are in contact with the microstrip line. The direct-deposition type, using Ni-Zn ferrite film 3μm thick, exhibited a strong transmission loss of 40 to 70% at 1.5-10 GHz, which far exceeds that obtained for commercial composite sheet type of noise suppressors (50μm thick), in which fine ferromagnetic flakes are dispersed in a polymer matrix. The sheet type suppressor using Ni-Zn ferrite film exhibited better transmission loss and reflection loss than those of composite sheet type of noise suppressor, though the ferrite film 5 μm thick was much thinner than composite sheet 50 μm thick.