Research On The Shielding Effectiveness Test Method Of Actual Shielded Shelter

With the increasingly harsh electromagnetic environment,the electromagnetic interference problem faced by electronic devices has become more and more serious.Shielding shelter is a platform for carrying electronic equipment.In order to deal with electromagnetic interference problems,the shelter is required to have good shielding performance.The shielding effectiveness test is a way to verify the shielding performance.The current shielding effectiveness test standard stipulates that the test should be carried out in the empty cabin state,but there is no specific test method for the actual shelter after the equipment is installed,and the current shielding effectiveness tests is mostly carried out in the frequencydomain,there is no uniform method for time-domain testing.Therefore,it is of great significance to study the shielding effectiveness test method of the actual shielded shelter and the equivalent calculation of the time-domain shielding effectiveness.This thesis takes the electronic equipment shelter as the research object,analyzes its shielding performance and shielding effectiveness test methods.The problems in the test of shielding effectiveness and the acquisition of shielding effectiveness in time-domain are studied.The main work and achievements of this thesis are as follows:In the first part,the shielding characteristics of electronic equipment shelter are analyzed.According to the typical shelter structure and the electromagnetic shielding principle,this thesis analyzes the influencing factors and requirements of the shielding performance of the shelter,and determines that the overall shielding effectiveness of the shelter depends on the weakest part of the shelter.Then,the shielding effectiveness testing method of shelter is introduced,and the shortcomings of the current testing method are pointed out based on the structure of actual shielded shelter.In the second part,the test method of shielding effectiveness in frequency-domain is discussed.The resonance of the shelter is analyzed by theory and numerical simulation,and the influence of different resonant modes is clarified.Through simulation analysis,a solution for the loading of absorbing materials to eliminate resonance is given.The simulation analysis of the test state blocked by the cabinet is carried out.The influence of the test distance change and the cabinet reflection on the test result is clarified.In the meantime,the calculation method of the correction value of the test result is given,and it is verified through the actual test.Through theoretical analysis and practical test,the influence of the antenna close to the wall on the test results is investigated,and some suggestions for practical test are given.In the third part,the index and testing method of time-domain shielding effectiveness are discussed.The advantages and disadvantages of time-domain shielding effectiveness and frequency-domain shielding effectiveness are compared.Aiming at the problem that there is no uniform standard for time-domain testing and the practical operation is not easy to implement,a method of calculating time-domain shielding effectiveness results using frequency-domain shielding effectiveness results is proposed.The equivalent calculation of shielding effectiveness in time-frequency domain is completed,and the feasibility of the method is verified by practical test.