Calibration of a Coaxial-Loaded Stepped Cut-Off Circular Waveguide and Related Application of Dielectric Measurement for Liquids

Abstract

A novel jig structure for S 11 calibration with short/open conditions and one reference material (referred to here as SOM) in dielectric measurement of liquids using a coaxial feed type stepped cut-off circular waveguide and a formula for exact calculation of S 11 for the analytical model of the structure using the method of moments (MoM) was proposed. The accuracy and validity of S 11 values calculated using the relevant formula was then verified for frequencies of 0.50, 1.5 and 3.0 GHz, and S 11 measurement accuracy with each termination condition was verified after calibration with SOM by combining the jig of the proposed structure with the study's electromagnetic (EM) analysis method. The relative complex permittivity was then estimated from S 11 values measured with various liquids in the jig after calibration, and differences in results obtained with the proposed method and the conventional jig, the analytical model and the EM analysis method were examined. The validity of the proposed dielectric measurement method based on a combination of the above jig structure, numerical S 11 calculation and the calibration method was thus confirmed.