Dielectric Measurement in Liquids via the Cut-off Circular Waveguide Reflection Method After Sil Calibration Using SOM Termination

In this study, S 11 at the front of the sample with a coaxial-feed type cut-off waveguide was measured in the frequency band of 0.50 to 3.0 GHz with liquids in the cut-off circular waveguide after S 11 calibration using SOM (short, open and reference material) conditions. The permittivity of liquids was estimated from the above S 11 based on 1. an inverse problem approach involving comparison with the S 11 value calculated using electromagnetic analysis via the mode-matching method, and 2. an estimation formula involving comparison with termination associated with SOM conditions. The Debye dispersion equation for calculation of methanol’s complex permittivity was corrected from the results. The dielectric constants of various liquids were estimated using a formula for comparison with three reference materials (pure water, methanol and air) using methanol after dielectric-constant correction. The effectiveness of the proposed method was verified by comparing the above estimated values with otherwise obtained outcomes. Moreover, the S 11 value of the jig was calibrated with short, open and another reference material (methanol) conditions after permittivity correction of methanol. The estimation results for the dielectric constant of pure water and similar after calibration were also compared with the above estimation values, and the reversibility of the proposed estimation method was verified. Favorable agreement of values estimated with each method was observed, indicating the validity of the proposed dielectric measurement procedure.