Measurement of complex permittivity of the highly absorbing liquids based on a two-layer circular waveguide in a wide frequency range

A waveguide-type cell for measuring the complex permittivity of strongly absorbing liquids in the frequency range of about two octaves is proposed. The cell is formed by a round metal waveguide with a coaxial cylindrical insert made of a dielectric with low losses. The liquid under study fills the space between the insert and the waveguide. The characteristics of modes of a two-layer waveguide with an absorbing layer of liquid are studied by means of numerical solutions of the characteristic equation for the two-layer waveguide. The results of electromagnetic simulation method used to wave excitation in such a cell are presented. The advantages of the proposed cell are compared to the known technical solutions used in the microwave dielectrometry of absorbing liquids.