Research On Shielding Effectiveness Analysis Method Of Electronic Equipment Enclosures Under Uncertainties

Electromagnetic shielding performance is an important technical indicator in the electromagnetic compatibility structural design of electronic equipment enclosure.The existing shielding performance analysis techniques mainly calculate the electromagnetic field inside the enclosure under the condition that all parameters are known,which cannot meet the analysis requirements of input parameters uncertainty that are widely existing in engineering.Based on the existing equivalent circuit model,this thesis studies the electromagnetic shielding characteristics analysis method of electronic equipment enclosure,obtains a more widely applicable analytical model of shielding effectiveness,and proposes a statistical analysis method of shielding effectiveness for complex enclosure structure based on statistics,which provides technical support and method guidance for the electromagnetic shielding structure design of electronic equipment enclosure under uncertainties.The main research contents are as follows:(1)A more widely applicable method for calculating the shielding effectiveness of enclosureFor the electromagnetic shielding problem of electronic equipment under interference,the equivalent circuit model of an enclosure containing ventilation board and dielectric plate structure is established based on the transmission line and waveguide theory.The coupling effect between apertures,the propagation of higher-order modes,and the influence of incidence direction and polarization direction of interference wave,etc.are taken into account.The shielding performance of the enclosure can be accurately evaluated in the wide frequency band of 0～3GHz.The validity of the equivalent circuit model is verified by using the full-wave electromagnetic field simulation software CST,and the influences of the geometric parameters,material parameters and position parameters of the dielectric board on the shielding effectiveness of the enclosure are analyzed.(2)The statistical analysis method of the shielding effectiveness based on polynomial chaos theoryFor the analysis of shielding characteristics of enclosures under uncertainties,the statistical analysis method of shielding effectiveness of an enclosure loaded with dielectric plate structure based on polynomial chaos theory is proposed.The equivalent circuit model of the enclosure is expanded by polynomial chaos using the Stochastic Galerkin Method and the Stochastic Collocation Method respectively.The accurate surrogate model of the shielding effectiveness is established,and the statistical properties of the shielding effectiveness under various random parameters are accurately evaluated.The validity of the statistical analysis method is verified by the Monte Carlo Method.Excellent agreement between the results of the proposed methods and that of traditional Monte Carlo Method can be observed.Significantly,for the case that including 5 random parameters,the Stochastic Galerkin Method and the Stochastic Collocation Method have2.5 times and 168 times acceleration over the Monte Carlo Method respectively,and the calculation efficiency of the Stochastic Collocation Method is about 68 times higher than that of the Stochastic Galerkin Method.(3)Numerical and analytical hybrid method for the shielding effectiveness of enclosures under uncertaintiesFor the electromagnetic shielding problem of an enclosure with complex PCB structure inside,the hybrid calculation method of the shielding effectiveness based on a PCB scattering parameter model is proposed by combining the full-wave transmissionline-matrix method and the equivalent circuit method,which improves the calculation efficiency by about 275 times with the same order of accuracy.After that,the hybrid model is further expanded by polynomial chaos theory,and the accurate surrogate model of the shielding effectiveness is established.Remarkably,the hybrid algorithm based statistical analysis method turns out to be far more efficient than the Monte Carlo Method.