A measurement method for ultra-wideband electromagnetic shielding effectiveness of thin materials

Shielding effectiveness is the core metric characterizing a material's electromagnetic shielding performance. With respect to measuring shielding effectiveness for thin materials over an ultra-wide frequency range, existing methods suffer from an inherent bottleneck: they cannot achieve broadband testing that simultaneously accommodates low-frequency cutoffs and high-frequency upper limits. To address the bottleneck where existing methods struggle to cover ultra-wide frequency bands starting from 10 MHz, this paper effectively overcomes measurement limitations within the 10 MHz-8 GHz ultra-wideband range by specifically optimizing the support medium and flange structures of the coaxial flange assembly. This establishes a comprehensive electromagnetic shielding effectiveness measurement methodology suitable for ultra-wide frequency domains. To verify the effectiveness and reliability of the proposed method, this study selected carbon nanotube materials as representative test samples for comparative validation experiments. The results show that the deviation between the values measured by this method and the standard reference values is less than 0.5%. A quantitative assessment performed in accordance with the Guide to the Expression of Uncertainty in Measurement confirms that the measurement accuracy of this method fully meets the electromagnetic shielding effectiveness testing requirements specified by the American Society for Testing and Materials, National Institute of Standards and Technology, and IEEE standards, thereby validating the accuracy and reliability of the proposed method for ultra-wideband measurements.