The effect of aperture shape, angle of incidence and polarization on shielding effectiveness of metallic enclosures

Apertures and slots of the enclosures come into prominence for heat allocation, ventilation, I/O cable, etc. These slots and apertures induce the coupling route of electromagnetic interference (EMI) from the inside to outside. So, electromagnetic shielding is usually used to decrease the emissions or to the progress of equipment immunity. In this paper, an effect of an aperture shape on the performance of electrical shielding effectiveness has been investigated by means of simulation. Rectangular, square, circular, equilateral triangle and hexagonal shape apertures that have a constant area of 5625 mm2 have been studied in addition to polarization type of applied electromagnetic field. It has been observed that ESE depends on the electric field direction and plane wave polarization and rectangular shape aperture has more effective ESE performance than square, circular, equilateral triangle and hexagonal type apertures. Rectangular shaped aperture has approximately 43 dB better performance than equilateral triangle one for whole frequency band of 100 MHz to 1GHz. Rectangular, square, circular, hexagonal and equilateral triangle type apertures have been ranked from best performance to the worst with respect to their ESE. There have been considerable findings that can be useful for enclosure designers about the effect of angle of incidence and polarization angle.