A study on the open-ended coaxial line method for measuring the permittivity of materials at microwave frequencies

The authors report the results of a study on the open-ended coaxial line method for measuring the complex permittivity of materials at microwave frequencies. The method is based on the quasi-static analysis of an open-ended coaxial line terminated by a semi-infinite medium. The complex permittivity of a 40% dioxane-water mixture at 25.1° is evaluated for measured admittance over a frequency range of 1 to 18 GHz. The results obtained compare favorably with the available experimental and theoretical data. The sensitivity of the measurement to the standard used is shown by measurements of 20% dioxane-water mixture using two different sets of standards. The limitations of this technique are also discussed