Development of a sensor for dielectric constant measurements utilizing time-domain measurement with a vector network analyzer

Abstract

In this study, a sensor with a signal transmission line for simple dielectric constant measurements was devised. The key feature of this sensor is that it utilizes the apex of a bended signal transmission line as a sensing portion. Its measurement principle is based on signal reflections caused by variations in the characteristic impedance of the signal transmission line due to the presence of materials under measurement around the sensing portion. The sensor was validated using the measurements of the dielectric constant of various resin materials. As a result, a substantially linear relation was obtained between the measured reflection coefficient and the dielectric constant of the resin material measured. Further, we concluded that the dielectric constant of the resin material could be evaluated in a simple and convenient manner using the devised sensor.