Accurate Complex Permittivity Inversion From Measurements of a Sample Partially Filling a Waveguide Aperture

In this paper, we propose a microwave method, which eliminates the necessity of precise knowledge of sample thickness for accurate permittivity determination of thin materials partially filling the waveguide aperture. The method utilizes propagation constant measurements at two different frequencies for this goal. To facilitate the proposed method for dispersive and nondispersive dielectric materials, we have employed a power series representation of the complex permittivity. We have validated the proposed method from permittivity measurements of prepared thin samples by different methods. We have also noted that the accuracy of the proposed method can be increased by the enhancements in the measurement accuracy of conventional methods, which require complete sample filling into the waveguide aperture.