Shielding Effectiveness Analysis of a Spherical Shield Made of Medium Conductivity Material against Low-Frequency Electric Field

With quasi-static field approximation, an analytic formula is derived for shielding effectiveness analysis of a spherical shield made of medium conductivity material (10 S/m-1000 S/m) against low-frequency electric field. The effects of frequency, material conductivity, and shield dimensions on shielding effectiveness are investigated. It is shown that the shielding effectiveness decreases at first and then increases with the frequency increasing from DC to MHz if the thickness of the shield is large. However, the shielding effectiveness decreases versus the increase of frequency continuously if the thickness is small. The shielding effectiveness can be enhanced by increasing either the material conductivity or the shield thickness. This research is helpful for the evaluation of composite conductive material for electromagnetic shielding applications.