Assessment of Shielding Effectiveness of Gaskets by Means of the Modified Bethe´s Coupling Theory

This paper investigates estimates for the shielding effectiveness (SE) of finger stock gaskets. Valuable insight into the nature of the openings principally responsible for coupling between gasket and mating surfaces are gained via a dipole characterization. It is shown that through visualization of the real contact area, the overall length of the engaged active contact region between fingers and their mating surfaces is generally smaller than the finger´s width, thus leading to an additional ldquoellipse-like´´ shape opening between two adjacent fingertips, which is much greater than the spacing slot. As a consequence, the dipole moment exhibited by the elliptic aperture is dominant and is responsible for the radiated fields into or from a shielding enclosure. Modified Bethe´s coupling theory for small apertures is applied to derive these fields and assess the SE of the gaskets. The validity and accuracy of the analysis become obvious in view of the good correlation with measurements.