Influencing factors of shielding effectiveness test of electromagnetic shielding clothing

Abstract

There is no perfect method to test and evaluate electromagnetic shielding (EMS) clothing up to now. The main reason is that the influence laws of the emission source parameters and the test position on the shielding effectiveness (SE) of the EMS clothing has not been clarified. In this paper, the SE of the EMS clothing is tested using a semi anechoic chamber in the frequency range of 1–18 GHz. The variation of the SE of the clothing is explored when the emission source parameters and the test positions are different. It is found that the SE of the EMS clothing decreases obviously with the increase of the testing distance, and the decline degrees are different with different frequencies. The decline trend slows down and approaches stability as the distance increases to a certain extent. The influence of the emission source angle on the SE is closely related to the frequency and positive or negative effects are produced at different frequency points. The SE are low when the test points are in the leakage areas with seams and openings, and the SE are high in the normal area. Under certain conditions, the measured SE of the clothing is close to zero or even less than zero. That is, a dangerous frequency point is formed. The mechanism of the above-mentioned laws is analyzed, and a new multi-index composite evaluation method is proposed to scientifically evaluate the EMS clothing based on the comprehensive consideration of the influencing factors. This research has great significance to promote the scientific test, evaluation and relevant standard formulation of the EMS clothing, and provides a reference role for the design and production of the EMS clothing.