| In the face of increasingly complex space electromagnetic environment,electronic instruments and equipment are vulnerable to electromagnetic wave interference.Shielding cavity can not only cut off the external electromagnetic wave,but also prevent the electromagnetic wave generated by internal instruments from entering the external environment.However,in practical applications,when the equipment inside the shielding cavity/casing needs to interact with the outside world for visual information,transparent optical windows should be set on the surface of the cavity.The optical window made of ordinary transparent materials has no electromagnetic shielding ability,leading to a serious decline in shielding performance of the shielding cavity.In this paper,metallic mesh is applied to the light window of shielding cavity,and the light window design,light window installation mode and edge treatment of shielding cavity are analyzed and discussed respectively.This paper first discusses the design rules of the light window of the shielded cavity,and USES CST STUDIO SUITE to analyze the influence of the size and position of the light window and the polarization mode of incident wave on the shielding efficiency of the cavity.At the same time,Robinson analysis method and its improvement method are used to compare with the simulation results.Next,it analyzes the improvement of shielding performance of metal mesh electromagnetic shielding light window installed in shielding cavity and conventional light window.In order to solve the problem of the large difference between the characteristic size of metallic mesh in micron scale and the size of shielding cavity in decimeter scale.The method of equivalent simulation of shielding light window is put forward,the metallic mesh window is equivalent to aluminum sheet,the feasibility of equivalent is analyzed,and then the edge gap of light window is equivalent to ring gap,which greatly improves the simulation speed.Simulation analysis shows that metallic mesh light window can significantly improve the shielding efficiency of the shielding cavity.For the analyzed shielding cavity,about13dB shielding efficiency is improved at low frequency.On the basis of equivalent simulation,the specific installation mode of shielded light window relative to shielded cavity is studied.The conductive connection between the electromagnetic shielding light window and the shielding cavity is discussed.The influence of six typical shielding light window installation modes on the shielding efficiency of the cavity is simulated and analyzed.The effect of using conductive adhesive to seal the shielding light window on the shielding efficiency of the cavity was analyzed.Finally,a 300×300×600(mm~3)aluminum shielding cavity with light window opening was designed and prepared,and metallic mesh window samples with diameters of 57mm and 100mm were prepared.A measurement system was built to test the shielding cavity in the range of 500MHz-6GHz.The experimental results verify the simulation conclusion:shielding efficiency of shielding cavity can be improved by the shorter side length of shielding light window perpendicular to the polarization direction of electric field,conducting the connection between the shielding light window and the shielding cavity in the direction of incident wave polarization,and the metallic mesh surface close to the side wall of the shielding cavity.The experiment shows that the shielding efficiency is improved by 20dB in the frequency band of 2GHz~6GHz when the metallic mesh light window is installed in the aperture of 100mm light window of the shielding cavity.The research of this subject provides the theoretical basis and design and installation ideas for the shielding cavity design with light window requirements,which is of great significance to the electromagnetic shielding protection of the instrument. |
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