A new method and apparatus for evaluating the electromagnetic shielding effectiveness of textiles

Abstract

Textile structures with electromagnetic shielding ability are widely used to attenuate the strength of electromagnetic fields, and their functionality is evaluated through direct measurement of their electromagnetic shielding effectiveness. Depending on the size of the shield and measured frequency range, various test methods can be used. There is still a need for development of a rapid testing procedure designed for special materials where only small samples are accessible. The paper presents a new convenient shielding effectiveness measuring procedure based on the modified shielded box method. The design, construction, and testing results of a new device are described in this paper. The proposed method is primarily designed for rapid comparative measurements of newly fabricated samples of relatively small size. Replacement of existing measurement standards is not the goal of this proposal. The main advantages of the new device and methodology are a small required sample size, no necessity of sample preparation to special shapes or dimensions, rapid measurements, and simple and cheap equipment in comparison with standardized equipment. To prove usability of the proposed method the electromagnetic shielding effectiveness of a textile sample set was tested with the help of the new method and the obtained results were statistically compared with those gained by the coaxial transmission line method based on ASTM D 4935-10. The agreement between results from the proposed and comparative methods was verified for textile samples with low and intermediate electric conductivity. Suitability, scope of application, benefits, and limitations of proposed measuring system are discussed.