A study on measurement accuracy of the dielectric properties in liquids based on a combination of an open-ended cut-off circular waveguide and comparison of expressions with reference material

This study involved examination of measurement accuracy differences associated with the introduction of an approximate expression (based on an equivalent circuit and comparison with a reference material) to the previously proposed cut-off waveguide reflection method by the authors. The insertion of various types of liquids with a plurality of frequencies was assumed. Specifically, dielectric properties were estimated by substituting the results of input impedance calculation using the mode-matching method to produce an exact solution into a comparison of expressions with a reference material. The insertion of various liquids featuring relative permittivities and loss tangents at frequencies of 500 and 1,000 MHz was assumed. Next, errors associated with approximate expression (i.e., measurement uncertainty) were clarified via comparison of estimated dielectric properties with actual dielectric property settings in electromagnetic analysis. The deference, validity and repeatability of measurement data obtained using the proposed method with actual insertion of certain liquids (under the condition that measurement was repeated) were compared with data from the approach previously proposed by the authors. The results indicated significant correspondence between the outcomes of each method and of variations in dielectric properties when measurement was repeated. Based on these outcomes, the results of measurement to clarify frequency characteristics associated with certain dielectric properties in octave-range frequency determination for certain types of liquids were also presented.