Application to an EMI Noise Filter of a High-Loss CoZrNb/SiO2 Multilayer Film

This paper reports the application of a magnetic alloy/nonmagnetic insulator multilayer film in EMI noise filters. The eddy-current skin effect in the magnetic alloy layers was used to achieve high-loss properties. The thickness of each layer and magnetic anisotropy of a CoZrNb/SiO2 multilayer film were designed such that the film would exhibit high-loss properties in the 30 to 1000 MHz frequency range. A noise filter tube was constructed incorporating such high-loss film, and a large impedance and noise attenuation for common-mode noise in this frequency range were confirmed. A noise filter tube was constructed with size reduced by a factor of ~100 compared with a conventional filter (ferrite core).