Application of negative permeability beyond ferromagnetic resonance frequency is discussed in this paper. Targeted application is the skin effect suppression technology for long wiring on high-speed and low-delay I/O board. An 11.9 μ m-thick Ni-Fe/Cu multilayer consisting of 0.25 μ m-thick Ni-Fe and 0.51 μ m-thick Cu in turn was electroplated, patterned into 609 μ m-wide and 40 mm-long signal line of microstrip line (MSL) on a 250 μ m-thick printed circuit board. Targeted frequency was 15 GHz, where relative real part permeability was supposed to be-2. The 40 mm-long Ni-Fe/Cu multilayer exhibited the insertion as small as 0.7 dB up to 25 GHz, which is almost the same as the copper monolayer MSL of the same geometry.
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