| The tendency of high frequency, high speed and high integration of a modern electric technology makes the environment where the electric equipments work more complicated. For air flow and heat dissipation, the shielding enclosure used to protect the electric equipment always needs the apertures which destroy the completeness of the enclosure. So the study of shielding effectiveness of an enclosure with apertures is very necessary and practical.The transmission line method are used for analyzing and predicting electromagnetic shielding characteristic of metal enclosures with single aperture ,an array of apertures and 2-layer model. Good agreements are obtained between the calculated results and those obtained by simulation software, which demonstrate the accuracy and validity of the approach.In this thesis, we first utilize the equivalent transmission line method to calculate the shielding effectiveness of a rectangular metal enclosure and discuss some parameters. Second ,we consider the rectangular aperture array as a combination of coplanar transmission line and the circular aperture array as parallel admittance. Then give the analytical expression for metal shielding enclosure with an array of apertures, focusing on incident plane wave with arbitrary polarization direction and the impact of the coupling between holes, And then propose an analytical formulation of holes varying from long side and wide side. At last but not least, 2-layer model considering higher mode and lossy material are derived, and then we discuss the impact of some parameters. All of the above are compared with simulation results from CST software, which verify the validity of the model. |
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