Study of reflection effect at fixture interfaces on permittivity measurements using the transmission/reflection method

We have evaluated the reflection effect at fixture interfaces in permittivity measurements using the transmission/reflection (T/R) method. In the T/R method, permittivity is derived from measured quantities without taken into account the reflections at fixture ends, thus they generate deviations of the results. From numerical calculations, we confirmed ripples due to multiple reflections are more pronounced in the frequency characteristic of the permittivity with increasing the reflection coefficient at fixture ends. We also performed permittivity measurements with the T/R method using four different types of fixtures. By comparing the resulting frequency characteristics of the permittivity, and by evaluating the uncertainties due to the connecting repeatability of fixtures, we clarified fixture-type dependence of the reflection effect on results of the T/R method.