A Simple Microwave Technique for Determination of Complex Permittivity and Thickness of High-Loss Planar Samples

A simple and accurate technique is demonstrated for determination of complex permittivity and thickness of high-loss samples in waveguides. The technique uses frequency as an independent parameter and assumes that complex permittivity does not change over very small frequency shifts. A set of equations are derived for the determination of complex permittivity and the uniqueness of them is shown. The measurements of high-loss cement paste samples are conducted for validation of the technique. It is shown that whereas the technique outputs less than 2 percent error in the determination of real part of the complex permittivity, approximately 6 percent error is observed for the determination of imaginary part of the permittivity. The thickness of the sample determined by the technique has a less than 10 percent offset from the actual one. The technique can be very useful for samples with almost constant electrical properties over a wide frequency range whenever the simplicity and low-cost are required.