Effects of Sample Thickness for Dielectric Measurements Using Transmission Phase-Shift Method

This paper re-studies the simple transmission phase-shift method for dielectric measurement of low-loss material. This method is explicit and material position-invariant. However, the sensitivity of transmission phase-shift is dependent on the material thickness. In this study, the effect of material thickness to the predicted relative permittivity of the material has been analyzed quantitatively. The sensitivity measurement was tested using customized X-band rectangular waveguide and three well-known materials, which are acrylic, FR-4 and RT/duroid 5880 substrate. Finally, appropriate thickness of the material in order to provide accurate predicted values of permittivity was determined.