Analysis of Radiated Emissions and Shielding Effectiveness for a Metallic Enclosure with Shielding Springs

The high speed digital processing in modern electronic products has made more difficult the achievement of conformity about limits emissions. To verify the requirements of standards on these emissions the use of a metallic enclosure is often necessary: in this way the power radiated by the system is reduced. In this paper the radiated emissions and the shielding performance of a metallic rack with shielding springs are studied both by dedicated experiments and by simulations. An internal source represented by a loaded monopole antenna is used to investigate the radiated emissions at 3 meters from the box. A simplified model of the antenna is proposed in the numerical model and a good agreement over a frequency range up to 1 GHz is achieved between measured results and simulated results. Shielding Effectiveness is finally evaluated by means of two different kinds of source: 1) near field (internal source) and 2) far field (plane wave source).