Permittivity measurement using a long fixture to eliminate reflection effect at fixture ends

We have developed a correction method of the reflection effect at fixture interfaces on permittivity measurements using the transmission/reflection (T/R) method. In the T/R method using a coaxial fixture, ripples and gradients often appear in the frequency characteristics of measured permittivities caused by reflections at fixture ends. We proposed to use a long air line as a fixture to distinguish reflection signals at sample interfaces from those at fixture interfaces. Measured S-parameters are analyzed in the time-domain by gating unwanted reflection signals, and then replacing them with estimated S-parameters to eliminate their effects. We validated the developed procedure by numerical calculations.