Complex Permittivity Measurement of Materials With a Wide Loss Tangent Range Based on Multiholes Cylindrical Resonant Cavity

A complex permittivity test method is proposed for materials with a wide loss tangent range (covering an order of magnitude from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-4}$</tex-math> </inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{0}$</tex-math> </inline-formula>) and multiple morphologies (solid, powder, and liquid). The test is based on a TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0<i>n</i>0</sub> cylindrical cavity, which has a central sample hole and two acentric sample holes, and the wide loss test is achieved by using different sample holes. Complex permittivity inversion algorithms for the acentric placement of the sample are proposed, where a tube for powder or liquid filling is considered. The validity of the proposed fixture and method is verified by simulation and test. For a sample with a radius of 3 mm, the measurable loss tangent reached 2.12. The proposed method has an important application for quickly obtaining the complex permittivity of unknown materials.