Shielding Effectiveness Analysis of Enclosure with Aperture by High-order Mode Transmission Line Model

An analytical formulation has been developed for shielding effectiveness calculation of rectangular enclosure with aperture. The theory has been extended to high frequency analysis by making use of high-order mode transmission line model. The number of high-order modes is according to the highest frequency. Analytical and simulation results prove high-order mode should be included when frequency is above the cut-off frequency of different modes. This paper investigates how many modes to choose in shielding effectiveness calculation in detail and gives a practical case, which is validated by simulation. Effect of aperture size, test point location, loss of enclosure as well as frequency can be obtained by the analytical formulation. In addition, shielding effectiveness of enclosure with PCB inside is also investigated.