An accurate method to estimate complex permittivity of dielectric materials at X-band frequencies

In this paper, a measurement method is presented to estimate the complex permittivity of a dielectric material even if its length is higher than the half wavelength in the waveguide. The Sij-parameters at reference planes in the rectangular waveguide loaded by material sample are measured by Network Analyzer. First of all, the expression of the complex permittivity as a function of Sij-parameters are calculated by applying the transmission lines theory. Further, a comparison of the estimated values of the complex permittivity obtained from the presented method and the Nicholson-Ross method is presented. Finally, the results for complex permittivity of Teflon, Nylon and Verde measured at the X-band frequencies are presented