Investigating the Impact of the Open-Ended Coaxial Sensor Design on the Reflection Coefficient Using the Method of Moments

Abstract

Reflection coefficient measurements are critical and widely used to determine the permittivity and moisture content of materials. The calculation of both the magnitude and phase of an open-ended coaxial reflection coefficient via the Method of Moments (MoM) is presented. The solution to the problem of calculating the reflection coefficient of the PTFE-filled coaxial sensor for air is obtained by converting the electric field integral equations into a linear system. The variation of the measured and calculated magnitude reflection coefficient as a function of frequency for air at room temperature was found to be 0.7 to 1.02. A comparison between MoM and the quasi-static method, using measured data, showed that MoM was closer to the measured magnitude. The phase reflection coefficient was also more accurate with MoM than with the quasi-static method. The calculation of the reflection coefficient using analytical (quasi-static) and numerical (MoM) methods for air as the sample was shown to compare favorably with the measured magnitude and phase of the reflection coefficient.