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,l) 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,l) modes enables continuous determination of the permittivity over operating frequencies. The characterization of the permittivity for even TE(1,0,l) 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.

Keywords

• aperture size
• cavity resonator
• complex permittivity
• perturbation technique
• rf/microwave sensor