Influence of metal enclosure shielding effectiveness on short penetrating conductor

The shielding effectiveness of a metal enclosure with a short penetrating conductor was studied in the frequency domain by using simulation and experimental observation. Electromagnetic simulation software computer simulation technology (CST) was used for simulations. Experimental system verifying the simulation results was built with a vector network analyzer, a power amplifier, a gigahertz transverse electromagnetic (GTEM) chamber, and an electromagnetic field measuring probe. The simulation and experimental results are in an agreement. Effects of different factors, such as length of a penetrating conductor, size of a penetrating aperture, and distance from observing points to a penetrating conductor on the shielding effectiveness were researched in the simulations. For a metal enclosure, its shielding effectiveness degrades about 30-40 dB when a penetrating conductor exists as a main coupling path, and about 10 dB more if the penetrating conductor outside the shielded enclosure is doubled in length. The shielding effectiveness degrades with increasing the size of a penetrating aperture or the distance from observation points to a penetrating conductor. The resonant frequency of the shielding effectiveness decreases when the length of a penetrating conductor inside the shielded enclosure increases. In order to improve the shielding effectiveness of an enclosure with a short penetrating conductor, the penetrating conductor should be short and the size of the penetrating aperture should be as small as possible, and circuits should be kept at a distance from the penetrating conductor. Effect of the penetrating conductor on the resonant frequency should be taken into account. The obtained results are useful for formulating guidances on design and installation of electronic products.