Measurement technology of complex permittivity based on split resonant cavity and hybrid field solution

This paper proposes a measurement technology of complex permittivity based on split resonant cavity and hybrid field solution. Compared to closed cylindrical resonant cavity, the split resonant cavity with an open design does not require samples to be fabricated into specific sizes, thus enabling non-destructive testing. In this paper, the split resonant cavity operates in TE01p (p = 1, 3, 5) mode, with a frequency range of 2-7 GHz and a highest quality factor of 7×104, which provides a good frequency selectivity and testing sensitivity. In addition, a simple hybrid field solution was designed for the split resonant cavity to solve the complex permittivity of the sample. In the cavity region, the electromagnetic field is modeled according to the field of a cylindrical resonant cavity, while in the sample region, the electromagnetic field is analyzed using the eigenmode expansion method. Subsequently, the mode-matching method is employed to determine the complex permittivity of the planar sample. Finally, through both simulation and experimental validation, the measurement technology proposed in this paper demonstrates high measurement accuracy and is well suited for non-destructive characterization of the complex permittivity of planar materials.