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Complex Permittivity Measurement of Low-Loss Anisotropic Dielectric Materials at Hundreds of Megahertz

Resonant methods are well known for their accuracy in determining the complex permittivity of materials. However, to guarantee the accuracy, interference modes must be suppressed in the measurement band. In this paper, a multi-mode split rectangular cavity is designed and fabricated to measure low-loss anisotropic dielectric materials in the frequency range from 300 to 1000 MHz. Details of the cavity design are presented. Simulation results for a uniaxially anisotropic material validate both the setup and the processing. Moreover, validation measurements on a sheet of polytetrafluoroethylene (PTFE) are in agreement with the literature data, which indicate that the proposed method in this paper is reliable and accurate for low-loss complex permittivity characterization at hundreds of megahertz.