An efficient circuital model is developed to predict the shielding effectiveness of an enclosure with an aperture array excited by a plane wave. First of all, the impedance of the aperture array is expressed as a function of the spacing between apertures, the radius of apertures, the incident angle, and the thickness of the perforated plate. Then, a multiple modes equivalent circuit method is proposed to evaluate the shielding effectiveness of the enclosure at frequencies up to multiple resonances region. Finally, the efficiency and accuracy of the method are demonstrated by comparing its results with analytical results from other equivalent circuit methods and numerical results from the transmission-line modeling method. The method outperforms the traditional equivalent circuit methods in that it takes into account several crucial geometrical parameters, the properties of the incident plane wave, the mutual coupling between apertures, and multiple modes propagation effect at the same time, thus having better accuracy. Meanwhile, the method provides a reasonable accuracy with a low computational burden, as compared with more complex numerical methods.

It is known that in applying the time-domain methods to study electromagnetic response of the system, the long time record required for generating accurate frequency domain results can be extrapolated from a relatively short time record by using Prony's method. In this paper, the electromagnetic shielding performances of two highly resonant enclosures with slot or aperture array are investigated by a combination of the finite-element time-domain (FETD) and extended Prony's method with a much smaller number of iterations. The procedure and details of using this combined method to investigate the shielding properties of highly resonant enclosures is demonstrated extensively. Moreover, some rules about selecting the parameters such as sampling position, sampling interval, sampling duration, and number of poles are proposed. As shown by comparison with the direct FETD generated results, the combined method achieves the same type of accuracy of frequency-domain delivered power with a FETD time record computed over a much shorter time duration.

The shielding properties of a rectangular enclosure with a doubly periodic array of apertures, exited by an obliquely incident and arbitrarily polarized plane wave is dealt with an improved method of moments (MOM) approach and mode-matching technique efficiently and accurately. Floquet waves for periodic structure are employed to represent the fields of the half-space, and the fields within the cavity are considered as superposition of waveguide modes. After enforcing the boundary conditions, MOM is used to obtain the shielding effectiveness and transmission coefficient. The proposed method has been successfully verified by a full-wave simulation tool CST and measurements. In our method, an arbitrary observation point is taken into account as well as higher order modes of the cavity. It is also found that all the resonant frequencies can be predicted from the transmission coefficient versus frequency curve.

Axial flow fans, used for heat dissipation in electronic equipment, may generate significant electromagnetic interference during PWM speed regulation. Due to its multiple radiation sources and relatively smaller size compared to the equipment, the radiation prediction model for equipment-level EMC analysis often involves a huge number of grids, which leads to computational difficulties and inefficiencies, and thus an equivalent modeling method for the electromagnetic radiation of PWM fan is presented. First, a detailed field-circuit coupling model of the radiation from winding and driving circuits is established using the time-domain finite-integral method with non-uniform grids. Then, a near-field hexahedron is defined to surround the fan, and the electromagnetic field of all its surfaces is derived based on the Huygens principle and calculated. Finally, the hexahedron encapsulating all radiation sources within the fan can be used in a higher level simulation as replicable and reusable equivalent sources. The proposed method is validated by a numerical example and actual measurements and applied to predict the radiation emissions within an electronic enclosure. The results show that the equivalent model can reduce 81.4% computation time and maintain good consistency in comparison to the detailed field-circuit coupling model.

This article presents an efficient statistical analysis of the shielding effectiveness (SE) of an enclosure with apertures under multiple uncertainties. It takes full advantage of the high efficiency of an extended equivalent circuit model and the versatility of the polynomial chaos theory to investigate the propagation mechanism of uncertainties from random input parameters to the SE. The uncertainties arising from fabrication tolerance and increasingly complex electromagnetic environment effects are embodied as parameters that follow Gaussian or uniform distributions. Important physical effects such as mutual coupling of apertures, propagation of higher-order modes, penetration of obliquely incident and arbitrarily polarized plane wave, and loading effect of dielectric plate are all taken into account to keep in line with practical scenario. Sensitivity analysis has been performed to investigate the influence of each random input parameter to the SE. A surrogate model has been established with expansion coefficients computed by using the stochastic Galerkin method and the stochastic collocation method. The results of the deterministic calculation and the statistical computation are validated by using the transmission-line matrix method in a commercial software and Monte Carlo simulation respectively.