Open-Ended Half-Mode Substrate-Integrated Waveguide Sensor for Complex Permittivity Measurement

Abstract

A novel open-ended half-mode substrate-integrated waveguide (HMSIW) sensor with dielectric flange for measuring complex permittivity of liquids, semisolids, and granular and particulate materials is presented. The open-ended HMSIW is designed and fabricated on FR4 substrate. The sensor model is described by using the aperture admittance model of open-ended waveguide. The complex permittivity of a given material is determined from measurement of the one-port reflection coefficient. For accurate measurement of the complex permittivity, the well-known three-material (air, distilled water, and 25% ethanol aqueous solution) calibration method was used. Complex permittivity of ethanol and 50% and 76% ethanol aqueous solutions measured with the HMSIW were in good agreement with those obtained by using an open-ended coaxial-line probe. In addition, results of measurements on saline solutions, gelatin samples, and canola seed samples of different moisture contents are shown.