Complex permittivity characterization through differential waveguide group delay measurement

This work presents a method for extracting the broadband complex permittivity of dielectric samples in rectangular waveguide. The method relies on the differential measurement of group delay and insertion loss of two samples with a known length difference, but unknown position in the sample holder waveguide. It is demonstrated by extracting the $\varepsilon_{\mathrm{r}}$ and $\tan \delta$ of a common stereolithographic printed resin from 18 to 27GHz in WR42 waveguide, with good agreement to prior estimates of the same material obtained by other methods.