An Improved Circuit Model for the Prediction of the Shielding Effectiveness and Resonances of an Enclosure With Apertures

Abstract

This paper presents an improved circuit model for the prediction of the shielding effectiveness and resonances of an enclosure with apertures. In the model, an aperture position factor is introduced to deal with an off-centered aperture. The factor considers the effect of higher order modes, and is thus more accurate than those considering the effect of TE10 mode only or considering the effect of higher order modes incorrectly. Moreover, because of the factor, multiple apertures are not required to be similar and can have arbitrary distribution. Three orthogonal components of voltage response are considered based on the waveguide theory; therefore, higher order modes including ${\rm TM}_{\rm mn0}$ modes can be predicted precisely, which are not possible with those previous circuit models derived from Robinson's model. Besides, monitor point can locate anywhere within enclosure and aperture can have arbitrary length–width ratio. The presented model provides a more accurate means for the prediction of the shielding effectiveness and higher order modes of an enclosure with arbitrarily positioned apertures over a wide frequency range compared with other existing circuit models, and costs much less solution time and fewer computing resources than traditional numerical methods. The validity of the presented model is verified by the transmission line matrix method.