Measurement of Complex Permittivity of Thin Plates Using Multimode of Split-Cylinder Resonator

A modified split-cylinder resonator (SCR) with open slits, which can suppress the vast majority of TM modes while lowering the quality factors of non-zero azimuthal mode TE modes, is proposed. Then, complex permittivity measurement at multiple frequencies of thin plates can be realized using multimode $\mathbf{TE}_{\mathbf{0}\boldsymbol{n}\mathbf{1}}(\mathbf{n}=\mathbf{1}\sim \mathbf{6})$. In addition, a cavity operating at 10–25 GHz was machined and two specimens processed from PTFE and RT/duroid 5880 were measured, and the experimental results are in good agreement with the reference data.