Complex permittivity of common dielectrics in 20–110 GHz frequency range measured with a Fabry–Pérot open resonator

Abstract

A Fabry–Pérot open resonator is a tool dedicated to broadband accurate microwave and mm-wave characterization of dielectric sheets. It has been applied in this paper to the measurement of the dielectric constant and loss tangent of various types of commonly used dielectric materials, such as semiconductors, electronic substrates, glasses, and plastics, in the 20–110 GHz range. The obtained results are in good agreement with the literature data, which are, however, often available only at discrete frequencies, thus making it difficult to recognize dispersive properties of the measured samples. It is shown in this paper that broadband measurement of high-resistivity and intrinsic silicon allows extracting their resistivity solely due to conduction losses. In the case of typical electronic substrates, it is shown that their dielectric constant is almost non-dispersive, whereas losses are, in general, linearly increasing with frequency. Glasses also exhibit almost non-dispersive dielectric constant, which is, however, larger than 3.8, whereas their losses can vary by over two orders of magnitude depending on the properties, like the hydroxyl content. The lowest dielectric constant is easily achievable in common plastics, spanning from ca. 2.03 for Teflon up to ca. 3.0 for PETG.