Permittivity measurements at millimeter wave frequencies using dielectric rod resonator excited by NRD-guide

A method of measuring the relative complex permittivity (ɛr = ɛ′ – jɛ″, tan δ = ɛ″/ɛ′) for low-loss dielectric materials at millimeter wave frequencies has been developed, using a dielectric rod resonator excited by the nonradiative dielectric waveguide (NRD-guide). Relative permittivity (ɛ′) and loss factor (tan δ) of the rod specimen are determined by the resonant frequency (f0) and unloaded Q-factor (Qu) of a TE0m1 mode resonator. The effective conductivity (σ) of conducting plates for short-circuiting the rod resonator is determined using TE021 and TE02δ mode sapphire resonators. Temperature dependence of ɛ′ and tan δ of sapphire and cordierite ceramics were evaluated at 60 GHz. This method has been adopted as the Japanese Industrial Standard (JIS R 1660-3) and is being prepared for the IEC international standard. Several standardized specifications are presented.