Continuous Characterization of Permittivity over a Wide Bandwidth Using a Cavity Resonator

Abstract

We examine a rectangular cavity resonator method to accurately characterize the complex permittivity of dielectric materials over a wide frequency range of 1–5 GHz by exploiting the fundamental mode and higher-order TE_{(1,0,<i>l</i>)} modes. For this purpose, a rectangular waveguide is coupled with a cavity resonator through a large inductive aperture. The permittivity characterization at both even and odd TE_{(1,0,<i>l</i>)} modes enables continuous determination of the permittivity over operating frequencies. The characterization of the permittivity for even TE_{(1,0,<i>l</i>)} modes suffers from potential errors due to the displacement of materials. This paper also proposes a method to compensate for these errors and improve the accuracy in the even modes. The experimental results of the fabricated cavity are presented using different materials (frequency-independent and frequency-dependent). The measured complex permittivity results show a good agreement with the reported results over a wide bandwidth available in the literature.