Measurement method of complex permittivity and permeability for a powdered material using a waveguide in microwave band

This paper proposes the measurement method of the complex permittivity and permeability for a powdered material based on measuring the effective permittivity and permeability using a waveguide in the microwave band. The powder of the silica and the ferrite were prepared for the verification of the proposed measurement method. In order to measure the S-parameter of these powdered materials, two open-ended waveguides infilled with a Teflon at the waveguide end and the sample holder, which is constructed from the same material as the waveguide, are fabricated. The powdered materials are filled into the sample holder in a number of volume ratios, which represent the ratio between the silica and air, the ferrite and air, respectively. The effective permittivity and permeability of the powdered materials are measured using the vector network analyzer for each volume ratio of the powdered materials in the frequency range from 4.0 to 5.8 GHz. The relationship between the volume ratios of the powdered material and the measured effective permittivity and permeability is derived for each measurement frequency. Then, the complex permittivity and permeability of the powdered materials are estimated by using the measured effective permittivity and permeability and the Lichtenecker's formula. In our measurement method, the Lichtenecker's formula, which is generally used for deriving the effective permittivity and permeability of a mixture, is applied to the estimation of the complex permittivity and permeability of only the material constituting the powder. We confirmed that the measurement results are in comparatively good agreement with the effective permittivity and permeability derived using Lichtenecker's formula. The proposed measurement method is considered to be effective as the measurement, which can be performed easily for a powdered material in the microwave band.