An improved waveguide method for accurate complex permittivity measurement of medium/high-loss material

In this paper, we propose an improved method for accurately measuring medium/high-loss material permittivity to overcome the air gap problem in the conventional waveguide method. This method improves the sample fixture and has a high tolerance on the wide side air gap, which is a dominant factor affecting the accuracy of the conventional waveguide method. Meanwhile, the proposed method avoids the effects of tilting and displacement during sample assembly. In our study, a typical lossy material commonly used in vacuum tubes has been quantitatively analyzed in Ka-band. The simulation results show that the relative error of ϵr′ can be reduced from more than 10% to less than 1% compared with the conventional waveguide method with a 0.1 mm wide side tolerance. The relative error of tan δ can be reduced from over 20% to below 6%. In addition, different lossy materials are discussed. The accuracy improvement was verified by measuring different BeO-TiO 2 samples using conventional and improved methods.