Shielding effectiveness of cylindrical enclosures with annular ring apertures

This paper presents an efficient numerical analysis of the shielding effectiveness of a cylindrical enclosure with an annular ring slot. The problem is initially divided into two parts using the field equivalence principle: one is the half free space with an incident wave and a magnetic current on the aperture surface and the other is the cylindrical enclosure with an extended section of a coaxial waveguide representing the annular ring slot. A mixed potential integral equation is formulated for the magnetic current in the aperture and the mode-matching method is employed to model the excitation of the cylindrical enclosure through a coaxial waveguide. Numerical results are presented and compared to those obtained by Ansoft's HFSS.