Introduction of an effective waveguide width in transmission/reflection methods for dielectric measurements

In this contribution a novel technique which improves the accuracy of the transmission/reflection method in rectangular waveguides is presented. The cross section of waveguides is often not perfectly rectangular or its width differs slightly from the nominal value. Such small geometric variations can be described assuming an effective width for the waveguide. In order to determine this quantity the transmission coefficient of an empty waveguide section is measured. For the determination of the dielectric properties of a material under test (MUT) the scattering parameters of the same waveguide section filled with the MUT is then measured. It will be shown that the accuracy of material measurements can significantly be enhanced if the effective width of the waveguide section instead of its nominal one is taken into account.