Abstract：With the trend towards high frequency and high power density power electronics, electro-magnetic interference from switching devices has become a critical factor affecting system reliability. Metallic enclosures with apertures are widely used to mitigate this interference, so accurate evaluation of their shielding effectiveness and internal resonance is essential. For cavities with multiple apertures, however, existing analytical approaches usually treat the apertures on different faces independently. The internal field at an observation point is obtained by superposing fields transmitted through each aperture, while electromagnetic coupling among apertures and the propagation of these coupled fields inside the cavity are neglected. As a result, some resonance points and local field enhancements cannot be predicted, causing resonant points and local field enhancements cannot be predicted, leading to an incomplete assessment of shielding performance. This paper develops an improved analytical method by incorporating electromagnetic coupling at the apertures. The method expresses the total electric field at an internal observation point as the vector superposition of the field produced by the incident wave directly exciting each aperture and the additional field generated by electromagnetic coupling and its propagation inside the cavity. The simplicity of field superposition is retained while capturing the interaction between apertures on different surfaces. The derivation is based on Bethe's small-aperture coupling theory and dyadic Green's functions. Each aperture is represented by an equivalent electric dipole and magnetic dipole at its center coordinates. For a given incident plane wave, the equivalent dipole moments associated with the directly transmitted field are obtained, and analytical expressions from the dyadic Green's functions of the rectangular cavity are used to calculate the internal electric field at the observation point. When coupling is ignored, the internal field is given by the superposition of the fields arising from the plane-wave components incident on each surface. In the improved formulation, Bethe's theory and the mirror theory are applied to determine additional equivalent dipoles associated with the coupled fields. The fields radiated by these coupling dipoles are again evaluated using the dyadic Green's functions and then vectorially added to the independently superposed field, thereby accounting for the effect of aperture coupling on the internal field distribution and the positions of resonance points. The algorithm applies to cavities with multiple apertures under arbitrary plane-wave incidence, for arbitrary aperture locations and internal observation points over a wide frequency range, provided that the apertures satisfy the assumptions of the small-aperture model. The formulation yields the frequency-dependent shielding effectiveness and the associated resonance characteristics. Numerical results are compared with CST full-wave simulations for various cavity configurations, aperture arrangements, incidence conditions, and observation points. The results show that the method can accurately and efficiently evaluate shielding effectiveness and resonance points for cavities with multiple apertures. The approach can be used to assess the shielding performance of enclosures in high-frequency, high-power-density power electronic systems and to examine the influence of cavity geometry, aperture parameters, and observation locations on internal field distributions and resonance.
黄海宏, 廖和其. 考虑异面孔缝电磁耦合的腔体屏蔽效能快速计算方法[J]. 电工技术学报, 2026, 41(16): 5375-5387.
Huang Haihong, Liao Heqi. A Fast Calculation Method for Cavity Shielding Effectiveness Considering Electromagnetic Coupling of Apertures on Different Surfaces. Transactions of China Electrotechnical Society, 2026, 41(16): 5375-5387.
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2026, Vol. 41 
