Complex permittivity measurements of lossy liquids at microwave frequencies

The TE010 mode cylindrical cavity was used for accurate complex permittivity measurements of lossy liquids at frequencies 7.4 GHz and 7.8 GHz. The complex permittivity was evaluated from measured resonance frequencies and Q-factors of the cavity with and without liquid under test employing rigorous electromagnetic analysis of the resonant structure in the complex frequency domain. Influence of the complex permittivity on the conductor losses in the cavity was taken into account in the complex permittivity determination. Several reference liquids have been measured including methanol, ethanol, 2-propanol and water showing good agreement with literature data. Uncertainty budget discussion proved high accuracy of this method.