Abstract
With the increase of electromagnetic interference (EMI) problems in digital information and communication devices, ferrite cores are often used to reduce the EMI level and improve the system immunity. For this reason, a need for measurement of complex permeability μγ of ferrite material, which determines the noise reduction effect, has been growing. In this paper, a practical transmission-line method is proposed for measurement of the complex permeability of ferrite cores in a broad-band frequency by scattering-parameter techniques. This measurement method tolerates the existence of air spaces between the measurement material and the coaxial-typed holder. Its validity is verified by fitting the measured results for commercially available ferrite cores having various dimensions to the Naito's formula and examining whether or not the measured results satisfy the Snoek's limit.
