A proposal of a new permittivity measurement method for low-loss materials

We have formulated a new permittivity measurement method for low-loss materials using a ring-resonator circuit made by transmission lines and directional couplers. This method can be used over broad-bandwidth nearly equal to operating bandwidth of transmission lines. We have measured S
₂₁
of the developed circuit and convert them to time-domain spectrums. We observed equally-spaced peaks with their amplitudes exponentially decayed. According to numerical calculations, directional couplers should have a low reflectivity coefficient and an optimized coupling factor in order to characterize dielectric properties of an encapsulated material from peak properties of time-domain spectrums of S
₂₁
.