Complex permittivity measurement method of high loss materials using cylindrical cavity resonator in millimeter-wave band

We proposed a new method to measure the complex permittivity of small biological tissue in millimeter-wave band using the TE_01n mode of a cylindrical cavity resonator. We examined the validity of the proposed measurement technique using an agar sample. The agar sample was maded by mixing pure water 98 % and agar powder 2 %. We prepared agar samples of different thickness ranging from 0.3 to 0.8 mm, and measured the complex permittivity between the 32 GHz-35 GHz band for each sample. It was assumed that the agar samples have approximately the same complex permittivity as pure water. We compared the measured value of agar sample with the theoretical values of water. As a result, when the thickness of the agar sample of 0.57 mm or less, the measured values approximately agreed with the theoretical values of water.