Electromagnetic Characterization of Thin Dielectric Materials From Amplitude-Only Measurements

A method is proposed for unique and accurate permittivity (ε
_r
) extraction of low-loss thin samples from reference-plane-invariant amplitude-only measurements without resorting to the information of explicit permittivity of a sample holder. Thanks to the amplitude-only measurements, it is possible to bypass the increased phase uncertainty of scattering parameters and retrieve unique ε
_r
. An uncertainty analysis is followed to investigate improved accuracy attained by our method. Waveguide measurements at the X-band are next conducted to measure ε
_r
of polyethylene and polyvinyl chloride samples with different lengths (the sample holder is a soda-lime glass) for validation of the method and for comparison its accuracy with other methods. From the comparison, we note that reference-plane-dependent methods necessitate precise knowledge of sample location for accurate ε
_r
retrieval. Besides, it is observed that while compared reference-plane-invariant techniques either require that the sample holder does not move while positioning the sample over it or produce more than one solution for ε
_r
measurement of low-loss dielectric samples, our method removes these two problems.