Broadband material characterization using traveling-wave whispering-gallery-mode dielectric resonators

Abstract

A new technique for broadband material characterization, using a whispering-gallery-mode (WGM) resonator, is proposed. The resonant perturbation method is applied for the measurement of both the dielectric constant and loss tangent of various types of materials and over a wide frequency band. A comprehensive study on the reliability of using such technique, via simulations and measurements, is conducted as well. The feasibility of this device in sensing small variations of the dielectric properties of the material is investigated. Furthermore, the geometry of the resonator is slightly modified to fit liquid materials as well. This can be a promising solution for sensing human-body tissues or liquids such as blood or urine due to the sensitive nature of these resonators. The experimental setup is successfully utilized to measure the dielectric constant of a water droplet as a liquid sample as well as different material samples of arbitrary shapes and dielectric properties. The measurements are performed over the whole X- and K-bands where the obtained results are with a maximum deviation of only 3.3% for solids and 4.5% for liquids.