Prediction And Modeling Of Anti-electromagnetic Interference On Electronic Equipment

With the rapid development in the field of electrical and electronic engineering,digital computer, information technology, instrumentation equipment, telecommunicationand semiconductor technology are gradually covering a very versatile and yet specializedfields of our lives. Electromagnetic shielding, which as a kind of designing techniquesfor electromagnetic compatibility, not only can protect the electronic or communicationdevices from EMI of the surrounding equipment, but also suppress the its uselesselectromagnetic wave to meet the emission limits. In practice applications, because of theexistence of the air vent, the video window, switch structure, I/O cable and other factors,these slots and holes provide directive electromagnetic energy coupling paths, resultingin serious SE degradation.The main content of the paper is divided into two parts: the influence on shieldingeffectiveness caused by the geometry parameters of the rectangular slot or circularaperture, incident angle or polarization direction of the EMI; the transfer impedance ofthe extremely narrow gap in different geometry parameters and electromagneticcharacter.Firstly, for electronic equipment, the upper frequency limit and the frequencybandwidth of the leakage signal are confirmed. The inference band and the waveform ofthe radiation source are also set up. The key simulation solver parameters to metal cavitySE and the resonance phenomena are discussed. The model of metal cavity withrectangular slots and circular apertures array are established. The geometry parameters ofthe slots or apertures, the incident direction and polarization direction of EMI have effecton the cavity shielding effectiveness.Secondly, the paper proposes an analytic formulation to examine the shielding ortransmission properties of multiply bent slots, by dividing it into a series of misalignedslots in different width and length. The formulation can be applied into some commonslots and has wide scope of frequency application.In the end, the development of transfer impedance applied to cavity shieldingeffectiveness calculation are introduced. The numerical formula describing therelationship between transfer impedance and shielding effectiveness. A simulationmethod of extremely narrow multiply bent slots in low frequency. Four models ofmultiply bent slots used to optimize the geometry parameters, such as width, the total path length, are set up. To change the electromagnetic character of material filled into theslots can also improve the cavity shielding effectiveness.The mentioned results provided strong theoretical basis for the fabrication and testof shield.