Characterizing Complex Permittivity of Thin Materials by Free-Space Transmission and Reflection Coefficients

In this letter, we introduce a permittivity characterization method for thin materials. It can operate without reference-plane calibrations in free space, reducing system complexity, especially at THz frequencies. The relevant solving formulas and resolution analysis are derived. Full simulations validate the proposed method and analyze its performance with different thicknesses and loss tangents, showing excellent performance for common materials. When applying the method to characterize the permittivities of different samples in the G-band, it provides accurate estimates, particularly for high-loss materials. Therefore, it is a proper candidate for permittivity characterization of thin materials.