Dielectric Measurement of Liquids via the Cut-off Circular Waveguide Reflection Method After S11 Calibration Using Three Reference Materials

In this study, S
11
for the front surface of the sample material was measured in the frequency band of 0.50 to 3.0 GHz with various liquids in the cut-off circular waveguide after S
11
calibration using three reference liquid materials, and the dielectric constants of the liquids were estimated as an inverse problem based on comparison of S
11
calculated from an analytical model using electromagnetic analysis via the mode-matching technique with the measured S
11
values described above. The effectiveness of the proposed S
11
calibration and the dielectric measurement method with three reference materials was verified by comparison with dielectric constants estimated after S
11
SOM (short/open conditions and one reference material) calibration termination. The frequency characteristics of complex permittivity for various liquids at 0.50 to 3.0 GHz after S
11
calibration with the reference materials as described above were compared with estimated values after S
11
SOM calibration, with results showing favorable agreement with each method. The study’s outcomes indicated the validity of the proposed S
11
calibration and dielectric constant estimation approaches.