Prediction of Shielding Effectiveness at Arbitrary Observation Points in Rectangular Cavities Based on the BLT Equation and Field Strength Relationships

This article presents an improved model for predicting the shielding effectiveness (SE) at arbitrary observation points within a rectangular enclosure, based on the Baum–Liu–Tesche (BLT) equation and the field strength relationship. The SE at the central observation point is initially predicted using the BLT equation. The relationship between the SE at two observation points located along the same section of the rectangular enclosure is derived from waveguide theory. Subsequently, the SE at arbitrary observation points is predicted based on the SE at the central observation point, for other points within the same section. The model accounts for the impact of eccentric apertures and higher order modes on SE by incorporating the aperture position factor, as well as the characteristic impedance and propagation constant of higher order modes. Furthermore, when the system operates under the main mode, the model allows for the use of simulations or experimental data to obtain SE values for known observation points, thereby enabling the direct prediction of SE at other observation points within the same section. This approach minimizes the need for repeated simulations or experiments, saving both time and cost.