Measurement of complex permittivity of moist sawdust by perturbation method with a dielectric ring resonator

This paper presents complex permittivity measurement of material using dielectric ring resonator. The method descried in the paper uses the perturbation method of dielectric ring resonator. In the conventional method, the value of one parameter in the formula of the perturbation method had been obtained using a standard sample and it was assumed as a constant. In our proposed method, it is obtained by the analytical solution of the dielectric ring resonator. Thus the measurement accuracy by the proposed method has been greatly improved. The proposed method was used to measure the permittivity of the sample of sawdust, of which the moisture content is from 0 to 120% on dry basis. The values of complex permittivity obtained by using HE211 mode and TE011 mode are in good agreement By the proposed method, the maximum difference for real and imaginary part of permittivity using the two modes are 5.8% and 5.0%, respectively. It was shown that the results are much better than that by the conventional method.