Study On Methods Of Fast Analysis And Improvement Of Shielding Enclosure Performance

The development of modern information technology has made more and more electronic and electrical equipment widely used in people's life,economic construction and national defense.However,electromagnetic interference in space environment has also increased,causing more potential electromagnetic hazards.Electromagnetic compatibility issues have become increasingly prominent.Shielding is an effective method of electromagnetic compatibility that blocks electromagnetic interference and protects electronic devices and systems.A common practice is to place a device or system in a metal enclosure.In practice,there are often slots,holes or arrays of apertures in the wall of the enclosure,which reduces the shielding performance of the cavity.In order to analyze the shielding performance of the enclosure,many scholars and experts have proposed various methods for calculating the shielding effectiveness.Among them,the equivalent circuit method has attracted attention in research due to its advantage of fast.And with the integration of electronic systems,this method has been improved and applied in recent years.The purpose of this dissertation is to quickly analyze and improve the shielding performance of the metal enclosure.Therefore,the basic principle of equivalent circuit method was studied in this dissertation.And based on this,a fast calculation method for shielding effectiveness of metal enclosure under complex conditions was developed.Combine this method and numerical simulation,some general methods have been proposed to improve the shielding performance of the enclosure.The main work of this dissertation includes:(1)A fast calculation method for shielding effectiveness of metal cavity in the case of installing a dielectric plate.The dielectric plate can be equivalent to the macroscopic model of the PCB circuit board or can be used as absorbing material.In order to quickly analyze the shielding effectiveness of the enclosure,based on the equivalent circuit method and the theory of coplanar strip transmission line,a new method was proposed to solve the shielding effectiveness of the metal enclosure when the dielectric plate is loaded.The calculated results agree well with the CST simulation results,which proves the correctness of the proposed method.(2)Expanded application of the fast calculation method.For more complex cases,such as the array of apertures on the metal wall,the aperture at any position and the observation point located anywhere in the enclosure,which is used for calculating the shielding effectiveness,the fast calculation method proposed in this dissertation was extended and improved to calculation the shielding effectiveness fast in the above complex cases.The calculated results are also in good agreement with the CST numerical simulation results,which proves the effectiveness of the expanded application of the proposed method.(3)Improvement of the shielding performance of the enclosure.As for the problems existing in the current metal enclosure,such as the potential hazard caused by excessive resonance and need for the improvement of shielding effectiveness,this dissertation proposed some general methods.The absorbing materials were loaded to suppress the resonance and the influence of the loading position and quantity on the resonance suppression was discussed.Suggestions for absorbing materials for different positions,thicknesses and quantities are given.The new carbon nanotube shielding material was used to improve the shielding effectiveness of the enclosure.Results show that the shielding performance is greatly improved over the entire frequency band.Besides,without changing the external size of the enclosure,a suitable number and size of T-shaped screws were installed inside to change the resonant frequency.The resonant frequency was deviated from the response frequency of the internal circuit to reduces the hazards.The proposed calculation method in this dissertation has a certain promotion effect on the development of the equivalent circuit calculation method,and is also beneficial to the optimization design of the shielding enclosure in more complicated cases in engineering.The general shielding performance improvement methods proposed in this dissertation also have a certain guiding role for shielding in practical engineering applications.