Millimeter wave measurement of Complex Permittivity by Perturbation method using Open Resonator

This article explains how to improve the measurement methods and the results to achieve the better accuracy of permittivity (relative dielectric constant epsiv´r) and tandelta (dielectric loss tangent) of thin films at 10-100 mum thick. A specimen´s thickness for an open resonator needs integer times of a wavelength to be measurable, so thinner specimens can not be measured by the open resonator. However, the use of the perturbation method made it possible to obtain the test results of permittivity and tandelta of ultra-thin specimens such as PTFE, FEP, a printed circuit board made of PTFE, identical to those by a measurement of thick specimens. It is important that the specimens be precisely placed and set in the center of the cavity