Multi-Frequency Measurements of Complex Permittivity of Dielectric Plates using Higher-Order Modes of a Balanced-Type Circular Disk Resonator

Abstract

A multi-frequency measurement method is proposed to determine the complex permittivity of dielectric plates. In these measurements, a balanced-type circular disk resonator excited in the center by coaxial cables is used to excite selectively only the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0m0</sub> modes having different values of integer m. The frequency dependence of the complex permittivity of the plates is obtained from the measured values of the resonant frequency and the unloaded Q of the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0m0</sub> modes for only one circular disk resonator. The numerical results based on the rigorous analysis are presented to explain the effects of the fringing field and coupling holes including coaxial cable. The usefulness of this method is verified by the measured results of polyolefin and PTFE plates