An improved approach for resonant measurements of complex permittivity of lossy liquids

An improved approach for evaluation of complex permittivity of liquids using a cylindrical microwave cavity at E/sub 010/ natural mode is presented. Evaluation is processed on the basis of measured electrical parameters of the cavity with a sample inserted into centered glass tube. The approach is based on the consideration of forced oscillations boundary problem for the cavity coupled to a measuring microwave circuit. Numerical evaluation of characteristic equation for the natural mode is used. Ohmic losses in cavity walls are taken into account in the field model employed. There is no limitations in permittivity and loss tangent values of materials measured. Comparison of complex permittivity values given by the approach being presented with ones given by the simple perturbation approach conventionally adopted in resonant measurements is done.