High-Precision Complex Permittivity Measurement of High Loss Dielectric Materials Using a Geometrical Gap in Millimeter Wave Frequency

Abstract

We proposed a newly devised method for measuring the complex permittivity of high-loss materials at the millimeter wave frequency range. In this paper, we employed a geometrical gap between samples, which allows us to evaluate the complex permittivity of high-loss materials. By introducing this gap, we obtain a characteristic shape of the transmittance, which enables us to fit the data and obtain a more precise complex permittivity value. The proposed method has been supported by experimental results with a very low error bar compared to the existing fundamental transmission line method. We measured diverse samples including alumina, Teflon, Vero family, and AlN-SiC, and confirmed that the proposed gap method achieves much higher precision than the existing method by 3 to over 10 times. Particularly for high-loss materials like the AlN-SiC sample, the average error of the relative permittivity evaluated by the existing transmission line method is 2.05% whereas the error by the proposed method is 0.05%. Moreover, the average error of the loss tangent measured by the existing method and the suggested method is 1.85% and 0.3%, respectively, which confirms the superiority of the proposed method.