Micromesh Research On Electromagnetic Field Distribution Of The Electrically Small Shielding Box With Apertures

Shielding protection is is a common problem in the industry of electrician,electric power and radio technology.The electromagnetic environment is increasingly complex,and the requirements of modern industry for electromagnetic shielding are also increasing,especially the requirements for compactness.When a shield is used to shield sensitive objects,the shield is usually perforated for wiring and ventilation purposes.The shielding effect near the opening is poor.In engineering,in order to ensure the effective shielding effect,the distance between the sensitive object and the opening is usually determined empirically,which is easy to cause excess margin and cannot meet the compact requirements of modern industry.Reasonable selection of the distance between sensitive objects in the shield body and the aperture needs to be based on the cognition of the fine distribution of electromagnetic field in the aperture shield body.However,most of the existing relevant studies focus on individual field points and high frequency band,and the research on the field distribution in the low frequency band range of the shield body is relatively lacking.In this paper,the electromagnetic field distribution of the electrically small shielding spherical shell with apertures is studied.Firstly,based on the superposition principle,the calculation model of the electromagnetic field inside the open-hole conductor ball under the action of external electromagnetic field in any direction is proposed.The analytical formula of the superposed submodel is derived in detail and its validity is verified by finite element simulation.Then,a finite element simulation model was built to explore the distribution law of electromagnetic field in the electrically small shielding box,and the distribution law of electromagnetic field under different opening conditions was analyzed.The direction of external electromagnetic field was considered to be perpendicular to the opening plane and parallel to the opening plane.The results show that the relative error between the simulation model and the theoretical calculation is less than 5%.The ratio of the isobdB line distance from the hole to the radius of the ball is approximately proportional to the central Angle of the hole,and the slope of the proportional relationship is greater with the larger the attenuation multiple.When two holes are opened in the electrically small shielding ball,the superposition principle is satisfied in the whole ball from the perspective of the field.As the two holes get closer,the relative error between the results of the submodel and the results of the total model is less than 10%when calculating the electric field,which means the superposition principle is satisfied when there is no area crossing between the two holes in the cases where the accuracy requirement is not very high,and the superposition principle is not satisfied in most cases when calculating the magnetic field.